Symposium Organizers
MarkD. Allendorf Sandia National Laboratories
Kendra McCoy Strategic Analysis, Inc.
A.Alec Talin National Institute of Standards and Technology
Stefan Kaskel Fraunhofer-Institute for Material and Beam Technology IWS
Symposium Support
Agilent Technologies UK Ltd
Defense Threat Reduction Agency (DTRA)
HORIBA Jobin Yvon, Inc.
National Institute of Standards and Technology
PANalytical
Quantachrome Instruments
Sandia National Laboratories
Sigma-Aldrich
Strategic Analys
UU1: Novel Synthetic Methods
Session Chairs
Tuesday PM, April 26, 2011
Room 2024 (Moscone West)
9:30 AM - **UU1.1
Functional Porphyrin-based Metal-organic Framework Materials.
Joseph Hupp 1 , Omar Farha 1 , Abraham Shultz 1 , SonBinh Nguyen 1
1 Chemistry, Northwestern University, Evanston, Illinois, United States
Show AbstractThis presentation will describe some strategies we have used to obtain and activate a substantial family of porphyrin-containing metal-organic framework materials featuring accessible porphyrin metal sites. These sites can be used to tether redox-active species and to interact transiently with a variety of candidate chemical reactants. Also to be described will be some applications of these materials, including catalysis-centered applications.
10:00 AM - UU1.2
Structural Control of Metal-organic Frameworks Based on Linear Linkers by Co-ligand Addition.
Trevor Makal 1 , Hong-Cai Zhou 1
1 Department of Chemistry, Texas A&M University, College Station , Texas, United States
Show AbstractMetal-organic materials, specifically porous metal-organic frameworks (MOFs), have shown considerable promise in applications including gas storage and gas separation. However, the numerous building units and abilities to bind in unexpected fashions continue to astound and baffle researchers. With this in mind, we investigate the effects of introducing linear N-binding co-ligands to the solvothermal syntheses of MOFs using large, linear ditopic organic linkers and cobalt or manganese metal salts. We show extension from nonporous 2-dimensional sheets, which feature ditopic paddlewheel secondary-building units (SBUs), to 3-dimensional porous frameworks composed of significantly different SBUs where addition of 4,4’-bipyridine is the only substantial modification to synthetic method. The effect of such a change in SBU and structure is emphasized in the significant differences in gas sorption abilities of the materials. Diligent selection of ligand and metal salts with relation to coordination mode, length, steric bulk and oxidation state all play significant roles in the control of SBU formation and connectivity in the crystalline materials. Current work continues to probe the control of SBU formation through modification of the N-binding co-ligand, as well as the extension of our large, linear ditopic linkers through both size and connectivity.
10:15 AM - UU1.3
Large-pore Periodic Mesoporous Quartz.
Paritosh Mohanty 1 , Manuel Weinberger 1 , Yingwei Fei 2 , Kai Landskron 1
1 Chemistry, Lehigh University, Bethlehem, Pennsylvania, United States, 2 Geophysical Laboratory, Carnegie Institution of Washington, Washington, District of Columbia, United States
Show AbstractPeriodic mesoporous silica materials were discovered by Mobil Oil in 1992 for petroleum cracking applications. It was envisaged that these larger pore materials would allow for a more effective processing of the heavier hydrocarbon molecules than microporous zeolite catalysts. However, this did not happen because the mesoporous silicas proved to be insufficiently hydrothermally stable, a consequence of their amorphous channel walls. In addition, the acidity of the amorphous walls of Al-doped mesoporous silicas, proved to be much less than that of crystalline Al-modified zeolites. Pressure very effectively promotes crystallization because crystalline phases are normally denser phases as compared to amorphous phases. The stress induced into chemical bonds by pressure kinetically activates the bonds which further facilitates crystallization. We report that large-pore periodic mesoporous quartz can be produced at a pressure of only 4 GPa, which is compatible with industrially used piston-cylinder high-pressure methods.
10:30 AM - UU1.4
The Growth of Single-crystal, (100) Oriented Hexacyanferrate Crystals on Au (111) using Electrodeposition.
Alec Talin 1 , C. Susut 1 , G. Stafford 1 , U. Bertocci 1 , B. McMorran 1 , A. Agrawal 1 , H. Lezec 1
1 CNST, NIST, Gaithersburg, Maryland, United States
Show Abstract11:15 AM - UU1.5
A Rational Synthetic Strategy to Incorporate Accessible Metal Centers in Metal-organic Frameworks.
Wonyoung Choe 1
1 Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States
Show AbstractMetal-organic frameworks (MOFs), assembled from organic molecules as linkers and metal clusters as joints, often resulting in robust frameworks with nanopores. Among numerous nanoporous MOFs synthesized, those MOFs with accessible metal centers are particularly interesting due to their potential in applications, ranging from heterogeneous catalysis to hydrogen storage. However, the rational synthesis of such materials has been a challenge to synthetic MOF chemists. Instead of creating accessible metal centers in metal nodes, we have been focused on creating these metal centers on the linker part using metalloligands. In this ‘metalloligand’ approach, the metal node does not have to play dual roles, namely structure building joints and functional metal centers. Separating these two roles in MOF synthesis is a crucial part of our synthetic strategy. Among the metalloligands, porphyrins are chosen because these macrocycles can accommodate various elements in the periodic table, ranging from transition metals to main group elements. In this talk, several synthetic pathways to create MOFs with accessible metal centers will be presented, together with interesting photochemical and catalytic properties associated with these MOFs.
11:30 AM - UU1.6
Combinatorial Synthesis of Multifunctional MOF via a Generic Post-functionalization Route: Application to Acid/Base Catalysis.
David Farrusseng 1 , Marie Savonnet 1 2 , Catherine Pinel 1 , Vincent Lecoq 2 , Dephine Bazer-Bachi 2 , Nicolas Bats 2
1 IRCELYON, CNRS, Villeurbanne France, 2 , IFP Energies Nouvelles, Lyon France
Show AbstractIt is acknowledged that ultimately MOFs could mimic “enzymes” using “molecular recognition” concept to allow high chemio-, regio-, enantio-selectivity. We could indeed anticipate MOFs as potential “artificial enzymes” that can combine several properties at the nanometer scale in a concerted fashion. However to date, the number of MOFs with more than one reactive “catalytic” function is rather scarce. A key to address advanced MOF materials suitable for more sophisticated applications is to add functionalities of greater complexity in a controlled manner. The ability to modify the chemical environment of the cavities within MOFs would allow tuning of the interactions with guest species, and serve as a route to tailor the chemical reactivity of the framework. However, the introduction of reactive chemical functions by self-assembly methods is not a trivial task. The post-synthetic modification (PSM) using covalent type grafting methods has seen outstanding evolution in the recent months. Nevertheless, methods developed so far are not very generic since they can be applied either to the most robust MOF due to relative harsh conditions or to linear or ramified alkyl (non functional) chains.We have recently reported an original PSM method starting from amino derived MOFs. The first step consists in converting the amino group into azide (N3). Without isolation nor purification, the desired functionalized material is obtained by grafting a the corresponding alkyne using “Clik Chemistry”.In this contribution, we show that our method can be applied to all kind of MOFs with respect to pore size range (micro to meso), chemical stability (low to high) and different degree of -structural flexibility and to all kind of grafted chemical functions (acid, coordinative, base, aromatic, aliphatic, hydrophilic). A diverse library of 48 original MOFs was synthesized and characterized. -to the best of our knowledge, this work reports for the first time the synthesis of two dimensional combinatorial library of functionalised MOFs. -we also show that we can control the grafting rate from 10 to 100%.-for the first time, we report the effect of the grafting rate and on the porous volume of the host MOF. -we will show that this method can be used to graft very reactive groups using protection/deprotection principles, -finally, this method was used to engineer catalytic MOFs for the transesterification of ethyldecanoate with methanol. Results show the linear increase of conversion with the increase of the degree of modification. The best performances are obtained for a multi-functionalized MOF which combined an optimum basicity/hydrophby balance.[1] M.Savonnet, et al, JACS, 2010, 132, 4518-4519
11:45 AM - UU1.7
Paving the Way to Multifunctional Catalytic MOFs via Non-traditional Post-synthetic Methods: Sulfonation and Chloromethylation.
Freek Kapteijn 1 , Jorge Gascon 1 , Maarten Goesten 1 , Jana Juan Alcaniz 1 , Enrique Ramos-Fernandez 1
1 ChemE, TUDelft, Delft Netherlands
Show AbstractThe last decade numerous publications on novel MOF structures have emerged, but recent years also advances in functionalization of these materials are progressing. Both pre- and post-synthetic approaches to incorporate functional groups have been presented. Pre-synthetic modifications, however, are limited due to the possibility of functional groups disturbing the synthesis of the MOF, or even coordinating to the metal. One-step post-functionalization on aromatic ring structures can be successfully achieved by electrophilic substitution, but in many cases it is difficult to extrapolate this to MOF chemistry due to the severe reaction conditions, and also provides only a limited amount of possible substituents. Post-synthetic functionalization through modification of pre-synthetically implemented amine groups is promising, but results in functional groups connected through C-N bonds while from a thermal and chemical stability perspective, C-C bonds would be preferred. Also, transforming - and therefore losing - the amine to a new functional group, is not the optimal route when going for the highly targeted multifunctional MOFs. In this work we present two mild methods to introduce strong functionalities in different –unfunctionalized- Metal-Organic-Frameworks: sulfonation and chloromethylation. With the first one we are able to introduce uncoordinated, covalently bonded sulfonate functionalities, resulting in microporous functional materials with a strong acidity and high proton conductivity. The second method, chloromethylation of the aromatic ring of MOFs opens the door for easy synthesis of multifunctional MOF systems, as the chlorine can be substituted by virtually any group of choice.The functionalized MOFs are characterized by MAS NMR, IR spectroscopy, XRD, Elemental Analysis, TGA and N2 sorption. These versatile routes to the functionalization of MOFs pave the way to a plethora of specific and multifunctional applications. Among them, special emphasis on catalytic applications will be paid in this work.
Symposium Organizers
MarkD. Allendorf Sandia National Laboratories
Kendra McCoy Strategic Analysis, Inc.
A.Alec Talin National Institute of Standards and Technology
Stefan Kaskel Fraunhofer-Institute for Material and Beam Technology IWS
Symposium Support
Agilent Technologies UK Ltd
Defense Threat Reduction Agency (DTRA)
HORIBA Jobin Yvon, Inc.
National Institute of Standards and Technology
PANalytical
Quantachrome Instruments
Sandia National Laboratories
Sigma-Aldrich
Strategic Analys
UU9: Poster Session
Session Chairs
Mark Allendorf
Alec Talin
Wednesday PM, April 27, 2011
Salons 7-9 (Marriott)
UU5: Membranes and Separations
Session Chairs
Wednesday PM, April 27, 2011
Room 2024 (Moscone West)
9:00 AM - **UU5.1
Crystalline Nanoporous Framework Materials and Composites for Protection and Decontamination.
Charles Bass 1
1 Physical Science & Technology Division, Protection and Hazard Mitigation DTRA-CB, Fort Belvoir, Virginia, United States
Show AbstractThe Defense Threat Reduction Agency – Joint Science and Technology Office – Chemical Biological Defense (DTRA-JSTO-CBD) has established a new thrust area dedicated to chemical biological defense research of Dynamic Multifunctional Materials. Under this area, crystalline nanoporous framework materials and composites have been identified as those that will drive development of technologies in areas such as protection and decontamination. Metal organic framework materials, in particular, show great potential to transform technologies across a broad range of applications. The promise of nanostructured materials is in the ability to design and tailor their chemical and physical properties. Also, crystalline structures allows for ease in development of modeling tools. This will lead to the predictive capabilities necessary to gain support for the use of such novel materials and technologies in Department of Defense applications. This talk will provide an overview of the JSTO-CBD Protection and Decontamination area and the needs, for which, crystalline nanoporous frameworks materials and composites may drive technological advancement.
9:30 AM - UU5.2
CO2/N2 Separation in Real Condition on an Ultramicroporous MOF Tubular Membrane (SIM-1): Effect of Pore Size and Process Evaluation.
David Farrusseng 1 , Sonia Aguado 1
1 IRCELYON, CNRS, Villeurbanne France
Show AbstractFor gas separation and solvent pervaporation, the manufacture of crystalline porous membranes is of prime interest. Although the synthesis of several zeolite membranes (including AlPO and SAPO) supported on porous ceramic bodies is now well established, the synthesis of new, defect-free crystalline molecular sieve membranes remains a challenge. Metal Organic Frameworks (MOFs) exhibiting tunable pore size are appealing new candidates for separation using membrane processes.Although the synthesis of supported thin MOF films has progressed rapidly, permeance data of a single gas on MOF membranes are scarce.Recently, Gascón and Kapteijn addressed the perspectives and current limitations of supported MOF membranes [1]. The major technological hurdle limiting the application of MOF membranes in chemical processes is the development of a manufacture process of tubular membranes that is reproducible and that can be implemented on a large scale. A second issue raised by Gascón and Kapteijn,is the effects of smaller pore size and the functionalization of the framework with pending groups on gas separation and also on catalysis appear to be very critical.Here, we report a very reproducible one-step process operating at atmospheric pressure to prepare thin MOF membranes on a long tubular support, which meets the first criterion enabling the scale-up for the preparation of large surface of membranes [2-3]. The second achievement of this work is the effective CO2/N2 separation under mixture and humid conditions. With respect to ZIF-7 and ZIF-8 membranes, this breakthrough result is obtained by combining a polar and bulkier linker resulting in a novel imidazolate-based MOF (SIM-1). In this paper, we will show:-the structure of the new ultramicroporous zinc imidazolate SIM-1,-the nature of the gas transport mechanism which takes place inside the framework,-the effect of the pore size on the adsorption features (ab inito modelling)-testing in real conditions, including the effect of water of the permeance rate and CO2/N2 separation factor-the process evaluation at large scale for CO2/N2 separation (OPEX and CAPEX) and comparison with conventional PSA/TSA processes. [1] J. Gascon et al, Angew. Chem., Int. Ed., 2010, 49, 1530[2] D. Farrusseng FR09/04488, FR09/04489[3] S. Aguado, New J. Chem., DOI:10.1039/C0NJ00667J
9:45 AM - UU5.3
Interplay of Metal Connector and Amine Functionalization in Flexible MOFs: Repercussions on CO2 Separation.
Pablo Serra-Crespo 1 , Jorge Gascon 1 , Freek Kapteijn 1
1 Catalysis Engineering, Delft University of Technology, Delft Netherlands
Show AbstractMetal Organic Frameworks that undergo a notable transformation of their lattice during adsorption/desorption are becoming of great interest, not only from the scientific point of view, but especially for the interesting adsorptive properties that some of them display. This phenomenon, rare in widely used micro-structured materials such as zeolites and other molecular sieves, occurs in several MOF families where the entire framework is supported by coordination bonds and/or other weak cooperative interactions. Despite the great interest in such flexible structures, very little is known about the mechanism that governs the dynamic behaviour of these frameworks.With the discovery of MOFs, it was only a matter of time until the combination of amines and flexibility was proposed for CO2 capture. Recently, we reported the excellent performance of the NH2-MIL-53(Al) in the separation of CO2 from CH4 (JACS 131(2009)6326).In this contribution, we present a combined experimental (performance, in situ DRIFTS, in situ XRD) and theoretical study (dispersion corrected DFT) of a series of group III elements based NH2-MIL-53(X) frameworks (X = Al, Ga, In, Sc). Spectroscopic and DFT studies point out only an indirect role of amine moieties. In contrast to other amino-functionalized CO2 sorbents and alcoholic amine solutions, no chemical bond between CO2 and the NH2 groups of the structure is formed, while in situ XRD and adsorption/separation experiments reveal that both the functional organic group on the linker and the metal modulate the “breathing” behaviour of the final material. That is, the capability of the adsorbent to alter its structure upon the introduction of specific adsorbates. With this knowledge in hand we are now able to formulate the fundamental requirements for the successful CO2 capture MIL-53 type materials. The high CO2 adsorption selectivity is driven by the preference for the formation of the narrow pore polymorph after the solvent removal. On the other hand, a rather facile opening of the MIL-53 structure is needed to accommodate larger quantities of carbon dioxide. In the case of NH2-MIL-53(Al) the associated energy losses are substantial. The flexibility of coordination polyhedra around the metal centers should be enhanced to ensure a smoother increase of the pore size upon the increasing CO2 pressure and thus allow for a larger CO2 adsorption capacity. This results in materials with unprecedented selectivities for CO2 capture, while maintaining a good regenerability, essential for practical application.
10:00 AM - UU5.4
MOF Based Gas Chromatography: A Comparative Study.
Florian Mertens 1 , Alexander Muench 1 , Juergen Seidel 1 , Tony Boehle 1 , Maria Lohse 1 , Diana Schindler 2 , Edwin Weber 2
1 Institut fuer Physikalische Chemie, Technische Universitaet Bergakademie Freiberg, Freiberg Germany, 2 Institut fuer Organische Chemie, Technische Universitaet Bergakademie Freiberg, Freiberg Germany
Show AbstractSeparation tasks were one of the earliest applications fields for MOFs discussed. In respect to chromatography, the use of packed columns appears to be an obvious choice. However, due to the recent developments in generating MOF based surface coatings using the controlled SBU approach [1] and self-assembled monolayers [2], new variants of PLOT (Porous Layer Open Tubular) columns for gas chromatographic applications can be fabricated. In this presentation we will demonstrate that the potential for these new systems is vast and for some standard separation tasks the performance of the state of the art technology is already surpassed. Given the fact that these results were already achieved without specific adaptation of the MOF system to the analytes investigated, a significant further performance increase can be expected. Since chromatographic performance in general cannot be judged by a single parameter comparison, we conducted a thorough, multidimensional analysis to support the claim. Kinetic investigations concerning the analyte - stationary phase interaction were carried out by classical van Deemter/Golay analyses. From these types of analyses, diffusional properties of various analytes in the MOF lattice can conveniently be derived and will be interpreted. Although MOFs would be particularly well suited for the exploitation of size selectivity as a possible means of effective separation because of the diversity of MOF pore sizes and shapes, some large pore MOF systems with small diffusional barriers also display excellent separation properties. This phenomenon will be demonstrated and explained by the analysis of a MOF based separation of the C1-C4 main natural gas components. [1] Steffen Hausdorf, Felix Baitalow, Tony Böhle, David Rafaja, Florian Mertens, J. Am. Chem. Soc. 2010, 132, 10978-10981[2] D. Zacher, O. Shekhah, C. Woell, R. A. Fischer, Chem. Soc. Rev. 2009, 38, 1418.
10:15 AM - UU5.5
Silver Impregnated Silica Inorganic Nanofiltration Membrane for Saltless Softening of Water.
Gordon Nangmenyi 1 , Ernie Lee 1
1 , A.O. Smith Corporation, Milwaukee, Wisconsin, United States
Show AbstractSilver impregnated silica nanofiltration membrane with an ultra high charge capacity offers very unique features which may provide a viable solution for saltless softening . Unlike ion exchange, no acids, bases, or salt solutions are required for regeneration of the system. Since no organic membranes or high pressure pumps are required, the new inorganic nanofiltration membrane offers operational advantages over the alternatives for ion exchange such as electrodialysis and reverse osmosis. With a high charge density, the silver impregnated silica nanofiltration membrane is capable of yielding large rejection values of Na+ and K+ from brackish solutions (>85%). The new membrane also displays the following: high flux due to hydrophilic nature of the membrane; low biofouling due to the inorganic matrix; effectiveness over a range of cations (Na+, K+, Ca2+, Mg2+, Li2+); effectiveness against microbiological contamination (bacterial inactivation, viral adsorption); low secondary waste after discharge of ions; and low wastewater volume for regeneration.
UU8: Sensors
Session Chairs
Wednesday PM, April 27, 2011
Room 2024 (Moscone West)
4:30 PM - **UU8.1
Design and Modeling of Microcantilever Sensors for Gas Detection using Metal Organic Frameworks.
Anandram Venkatasubramanian 1 , Ilya Ellern 1 , Jin-Hwan Lee 1 , Vitalie Stavilia 2 , Mark Allendorf 2 , Peter Hesketh 1
1 Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 , Sandia National Laboratories, Livermore, California, United States
Show AbstractMicrocantilevers are exquisitely sensitive transducers that have received a great deal of attention for chemical and biosensing applications [1]. To increase the selectivity we have investigated nanoporous coatings of Metal-Organic Frameworks (MOFs) which have a very high surface area and well defined pore sizes. MOFs have been used for gas storage, gas purification and separation applications [2,3], however, little focus has been given to gas sensing. Our past work has demonstrated that the MOF Cu3(BTC)2 could be grown on a microcantilever surface and used to detect gases at room temperature [4] and to detect volatile organics [5]. This paper focuses on stress induced sensing mechanism with different MOF materials and different cantilever geometries and a comparison with mechanical modeling. The microcantilever arrays with, n-type piezoresistive strain sensing are of length 230 µm and width 100 µm. They were fabricate,d using standard MEMS batch fabrication processes with both oxide and nitride structural layers forming the cantilever beam. The resonant frequency of the cantilevers is measured with optical displacement system to determine the amount of MOF coated on each cantilever. The microcantilever sensors are placed in a custom designed flow chamber with heating to remove water vapor. The stress response was obtained by the subtraction of the uncoated reference microcantilever response from the MOF-coated cantilever response using a Wheatstone bridge. The substantial resistance changes with MOFs exhibited a fast response time, strong, and completely reversible response for adsorption and desorption. The measured response shows concentration dependence that conforms to Langmuir type behavior. Modeling of the thermomechanical behavior of the MOF has been undertaken with COMSOL multiphysics modeling software to examine the effects of cantilever geometry, MOF coating thickness and properties on the sensor response. The microcantilevers with different dielectric layers produced the maximum response up to a MOF coating thickness of 1500 nm. However for designs with silicon dioxide dielectric, at the top produce a slightly better response than the nitride coated beams for a MOF layer of the same thickness. With a MOF coating on both sides of the cantilever improved response is possible for MOF thickness of greater than 600 nm. From these simulations the optimum design for the cantilever to yield the best response has been identified.REFERENCES:1. K. M. Goeders, et.al., Chem. Rev. vol. 108, pp. 522-542 (2008)2. See special issue, Chem Soc Rev., vol. 38(5), pp. 1201-08 (2009)3. K. Uemura, et.al., Desalination, vol. 234, pp. 1-8 (2008)4. M. D. Allendorf, et.al., J. Am. Chem. Soc., vol. 130, pp. 14404-05 (2008)5. J. H. Lee, et.al., Proceedings of SPIE, Micro- and Nanotechnology Sensors, Systems, and Applications II, Vol 7679, No.7679-27 (April 2010).
5:00 PM - UU8.2
MOF Films for Microsensor Coatings.
Alex Robinson 1 , Mark Allendorf 2 , Steve Thornberg 1 , Vitalie Stavila 2 , Peter Hesketh 3
1 , Sandia National Labs, Albuquerque, New Mexico, United States, 2 , Sandia National Labs, Livermore, California, United States, 3 School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractMetal organic framework (MOF) materials are a class of hybrid organic-inorganic crystalline materials whose pore structures and chemical properties can be tailored by the selection of component chemical moieties. Many MOFs have extraordinary intrinsic surface areas, capable of adsorbing large quantities of other chemicals, such as volatile organic compounds or moisture. Upon absorption of guest molecules, many MOFs undergo reversible changes in the dimensions of their unit cells. These properties suggest several routes to chemical sensing in which the transduction mechanisms are: 1) the stress induced at an interface between a flexible MOF layer and a static microcantilever fabricated with a built-in piezoresistive stress sensor; 2) a change in the resonant frequency of an oscillating microcantilever induced by mass adsorption; and 3) a change in the resonant frequency of an acoustic sensor, such as a surface acoustic wave (SAW) sensor through changes in mass and film moduli. We will present data on these sensors, demonstrating highly sensitive chemical sensing over a very broad sensing range. The dimensions and scalability of microsensors combined with the tailorability of MOFs opens the possibility for highly discriminating chemical sensor arrays beyond the capability of commonly used polymer films.Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.
5:15 PM - UU8.3
Computational Modeling of Low-pressure Gas Detection in Nanoporous Framework Materials.
Todd Zeitler 1 , Mark Allendorf 2 , Jeffery Greathouse 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , Sandia National Laboratories, Livermore, California, United States
Show AbstractWhile much attention has been paid to the extraordinary properties of NFMs for gas storage, it has become apparent that low-level gas detection (< 5 mbar P/Po) is also possible with these materials. However, synthesis and low-pressure testing of NFMs is expensive and otherwise problematic. Computational modeling of adsorbate-NFM interactions overcomes these challenges by allowing for both efficient screening of existing structures and identifying desired molecular properties of potential new structures. In the current work, grand canonical Monte Carlo simulations of methane adsorption by NFMs are used to screen candidate materials for their low-level gas adsorption properties. Members of the MOF-74-M series (M=Mg, Co, Ni, Zn) and a set of Cu-based MOFs show 2-5 times greater adsorption over a set of COFs and high surface area Zn-based MOFs at 50 mbar P/Po. Our results also show that methane adsorption can be incrementally enhanced by functionalizing organic linkers of existing NFMs. For example, MOF-74-M series materials show a 25-45% enhancement in methane adsorption with amine functionalization. The results from computational modeling of adsorbate-NFM interactions—via large-scale screening, as well as modeling of novel structures—can be used to guide synthesis of NFMs for low-level gas detection applications.Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
5:30 PM - UU8.4
Influence of MOF Structure on Luminescence and Energy Transfer.
Patrick Feng 1 , John Perry 1 , Scott Meek 1 , Fred Doty 1 , Mark Allendorf 1
1 , Sandia National Labs, Livermore, California, United States
Show AbstractNumerous examples of Metal-organic frameworks exist that exhibit notable variations in structural and crystallographic properties, including interpenetration, host-guest interactions, and dynamical effects such as “breathing.” This paper describes the relationships between these structural and electronic effects and the observed luminescence properties in a diverse series of MOFs, with an emphasis on energy transfer via intra- and intermolecular interactions. Implications for radiation detection and optoelectronic applications are discussed.
UU9: Poster Session
Session Chairs
Mark Allendorf
Alec Talin
Thursday AM, April 28, 2011
Salons 7-9 (Marriott)
9:00 PM - UU9.1
Thermal Amorphization of Zeolitic Imidazolate Frameworks: The Ubiquitous a-ZIF.
Thomas Bennett 1 , Jin-Chong Tan 1 , David Keen 3 4 , Andrew Goodwin 2 , Emma Barney 4 , Anthony Cheetham 1
1 Materials Science and Metallurgy, Univerisity of Cambridge, Cambridge United Kingdom, 3 Physics, Unviversity of Oxford, Oxford United Kingdom, 4 , ISIS Facility, Didcot United Kingdom, 2 Chemistry, University of Oxford, Oxford United Kingdom
Show AbstractZeolitic Imidazolate Frameworks (ZIFs) are a family of Metal-Organic Frameworks (MOFs) which display network topologies analogous to those seen in zeolites, whereby the zeolitic building blocks of corner-sharing SiO4 tetrahedra are replicated by MN4 tetrahedra linked by imidazolate anions. Interest has focused mainly on the tuneable gas sorption and separation properties of these porous materials. The retention of thermal stability derived from their zeolitic structures makes them particularly attractive candidates for practical applications. Inorganic zeolites are known to undergo pressure– or temperature–induced amorphization. The amorphous materials thus formed can retain some aspects of crystalline topology, and consequently be of low entropy. Polyamorphism (the presence of structurally isomeric amorphous phases differing in density and entropy) has been identified both experimentally and theoretically in these materials. Given the often made similarities between ZIFs and zeolites (ascribed to the common subtended angles of ~145° at the metal-bridging species), it is perhaps not surprising that reports of pressure-induced ZIF phase transitions and amorphization exist, albeit at pressures far lower than their zeolitic counterparts. In recent work, we demonstrated the formation of an amorphous ZIF (a-ZIF) with a network topology comparable to that of silica glass, through the thermal amorphization of the crystalline Zn-based ZIF-4 framework. More remarkably perhaps, the temperature of amorphization is comparable to that of purely inorganic zeolites. The mechanical properties of the a-ZIF were studied by nanoindentation, being found to be isotropic and intermediate between ZIF-4 and ZIF-zni, the two bounding crystalline phases.In the present work, we show that a-ZIF and crystalline ZIF-zni can also be prepared by heating two structural isomers of ZIF-4. Zn-based ZIF-1 and ZIF-3, possessing the zeolitic topologies BCT and DFT respectively, undergo amorphization and recrystallization to ZIF-zni at similar temperatures to that of ZIF-4. We also demonstrate the same process in a cobalt analogue of ZIF-4, (Co-ZIF-4) yielding an amorphous material with potentially interesting magnetic properties. Variable Temperature PXRD, Gas Pycnometry, X-ray total scattering and nanoindentation techniques are all used.Based on our observations, it is to be expected that all other ZIFs encompassing an unsubstituted imidazolate linker (specifically ZIF-2, ZIF-6 and ZIF-10) will undergo thermal amorphization, it following necessarily that this subsection of the ZIF class of materials is not as thermally stable as other members of the family.No evidence of polyamorphism in the Zeolitic Imidazolate Framework family has been found thus far, the a-ZIF being formed regardless of which unsubstituted ZIF is thermally treated. This work has important consequences for the selection of ZIF candidates for practical application.
9:00 PM - UU9.10
Synthesis and Characterization of Nano Structured AlON and GaN Using Mesoporous Carbon Nitride as Hard Template as Well as Reactive Template.
Siddulu Talapaneni 1 3 , Vinu Ajayan 1 3 , Mori Toshiyuki 2 3
1 Material Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki, Japan, 3 Department of Chemistry, Hokkaido University, Sapporo, Hokkaido, Japan, 2 Center for Fuel Cell, National Institute for Materials Science (NIMS), Tsukuba, 116, Japan
Show AbstractMetal nitrides have been receiving much attention in recent years owing to their excellent properties such as extreme hardness, high thermal and mechanical stability, and semiconducting ability. These properties made them to be available for various applications including optoelectronic devices, catalysis, supercapacitors. For the applications such as catalysis and supercapacitors, the control of the nanostructure and the textural properties such as surface area, and pore volume of the metal nitride are extremely important as they dictate the efficiency of the materials in those applications. However, unfortunately, there has been no report on the nanostructure metal nitride with very high surface area. Here we introduce a new concept of making nanostructures metal nitride materials using nanoporous carbon nitride as templates and the nitrogen source. It was recently reported that two dimensional nanoporous carbon nitride materials with different pore diameters and surface areas can be fabricated. Although the materials were interesting, the nitrogen content of the material was low. In this manuscript, we report the synthesis of highly ordered nanoporous graphitic carbon nitride with C3N4 stoichiometry using three dimensional nanoporous silica KIT-6-150 as hard template and cyanamide, aminotriazole and aminotriazines are the precursors. These materials exhibit a high surface area (300 m2 g-1, 260 m2 g-1 and 560 m2 g-1), a high nitrogen content, and large pore volume. Highly ordered nanostructured AlON and GaN was also fabricated using this three dimensional nanoporous graphitic carbon nitride with C3N4 stoichiometry as template. The obtained nanostructured AlON and GaN are highly pure and exhibits high surface area and high crystallinity. More structural details of the nanostructured AlON, GaN and nanoporous carbon nitride materials will be presented during the conference.1.Vinu, A, Adv. Funct. Mater. 2008, 18, 816-827.
9:00 PM - UU9.11
Synthesis of Mesoporous Titanium Dioxide – Metal Oxide Composite Materials with UV-light Blocking Properties.
Minyoung Yoon 1 , Sang Hoon Jeon 2 , Sun Sang Kwon 2 , Yeong Jin Choi 2 , Ji Man Kim 1
1 Department of Chemistry and BK21 School of Chemical Materials Science, Department of Energy Science, and SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, Gyeonggi-do, Korea (the Republic of), 2 R&D Center, Amorepacific Corporation, Yongin, Gyeonggi-do, Korea (the Republic of)
Show AbstractCrystalline titanium dioxide (TiO2) is one of the most important wide band gap semiconducting materials and is widely investigated for use in photoelectrolysis, photocatalysis, heterojunction solar cells, environmental purification, and gas sensing. Especially, the TiO2 materials have been also attracted much attention as sun-screening materials in cosmetics, due to the excellent UV-light blocking (or absorbing). In the present work, we have synthesized mesoporous TiO2 with crystalline framework and high surface areas. In order to enhance the UV-light blocking property, various kinds of metal oxides have been loaded within the mesopores of TiO2 materials. The physicochemical properties of TiO2-based composite materials thus obtained have been investigated by using X-ray diffraction technique, N2 adsorption-desorption analysis, scanning electron microscope, transmission electron microscope, and UV-visible spectroscopy. Metal oxides loaded mesoporous TiO2 materials exhibit higher UV-light blocking effect than the TiO2 materials without other metal oxides, which is probably due to increase of reflective index and enhancement of UV/VIS absorption properties.
9:00 PM - UU9.13
ZIFs Can Breath!
David Farrusseng 1 , Sonia Aguado 1 , Pera Titus Marc 1 , Virginie Moizan 2 , Carlos Nieto-Draghi 2 , Nicolas Bats 2
1 IRCELYON, CNRS, Villeurbanne United States, 2 , IFP Energies Nouvelles, Lyon France
Show AbstractSoft porous crystals that exhibit dynamic frameworks upon external stimuli such as variations of pressure, temperature or electric field are the latest generation of porous solids. They are bi(multi)stable crystalline materials with long-range structural ordering that possess a structural transformability. The phase transformation can take place when a guest molecule is adsorbed or removed from the network. This property is very attractive for designing new generations of adsorbants or sensors using “gate-opening” features.First porous Zinc imidazolates were discovered by Huang et al [1]. In these solids, tetrahedral Zn(II) are solely coordinated by nitrogen atoms of the imidazolate bridging ligand. These solids were reexamined by Yaghi and co-workers, who extended this class of porous coordination polymers to 90 novel structures by high throughput screening [2]. Because the Zn-im-Zn linkage is similar to the Si-O-Si linkages found in zeolites, the zinc imidazolate solids usually crystallize in the same topologies as do aluminosilicates. These structures are therefore referred to as Zeolite Metal-Organic Frameworks (ZMOF) [3] or, more frequently, as Zeolite Imidazolate Frameworks (ZIF) [2]. Their high hydrothermal, chemical and thermal stability further reinforce their similarity to zeolites. ZIF materials are, however, not as rigid as zeolites. For example, Cheetham et al. reported that the sodalite cell of ZIF-8 can shrink or expand, to a limited extend, under pressure due to rotation of the linkers. More recently, the same team has shown that upon heating, ZIF-4 undergoes a reversible transformation from the crystal to the amorphous state [4].In this study, we show for the first time that ZIF-XX exhibits a reversible breathing effect upon changes in temperature or CO2 partial pressure. The thermodynamics of the process were studied in detail and compared to other reference flexible MOFs. We demonstrate that a reversible phase-to-phase transformation is responsible for this phenomenon. To the best of our knowledge, this constitutes the first example of a guest-induced gate-opening ZIF.1.X. Huang et al, Angew. Chem., Int. Ed., 2006, 45, 1557 ; Chin. Sci. Bull., 2003, 48, 1531.2.K. S. Park et al, Proc. Natl. Acad. Sci. U. S. A., 2006, 103, 10186.3.Y. Liu, et al, Chem. Comm., 2006, 14, 1488-1490.4.T. D. Bennett, et al, Phys. Rev. Lett., 2010, 104, 115503.
9:00 PM - UU9.14
Engineering the Environment of a Catalytic MOF by Postsynthetic Hydrophobization: A Next Step Towards Artificial Enzymes.
David Farrusseng 1 , Jerome Canivet 1 , Sonia Aguado 1
1 IRCELYON, CNRS, Villeurbanne France
Show AbstractHeterogeneous catalysis is of paramount importance in many areas of the chemical and energy industries. However the air moisture or the water formed during the organic transformation often hinders the reaction or limits the reaction rate due to poisoning effects. This motivates the design and the engineering of catalytic materials with hydrophobic features to avoid water-induced catalyst poisoning, as the hydrophobic outer shell of enzymes do.Due to their calibrated pore size, they are regarded as new shape selective catalysts with respect to zeolites. MOFs have been already reported to catalyze a broad range of organic transformations involving their Lewis acid nodes as well as their Brønsted acido-basic properties. Many reports deal with carbon-carbon bond formation catalyzed by unmodified MOFs.In order to get more sophisticated MOF-catalysts many research teams examined the functionalization of those materials. Cohen and co-workers extensively studied the covalent organic PSM of a variety of amino-functionalized MOFs. Furthermore Cohen extended his study to the hydrophobization of amino containing MOFs through amide coupling in order to increase their moisture-resistance. In a parallel work, Yaghi et al. also reported the functionalization of porous materials and especially the reactivity of the ZIF-90 against an amine or a reducing agent. However, the catalytic effect of the functionalization of MOF by hydrophobe agents has not been reported so far.In contrast to previous studies, our methodology is based on the modification of the environment of the catalytic centers and not on the insertion of new sites on the MOF structure. We thus studied the ability of modified ZIF materials to accelerate the reaction rate involving water formation. We chose the Knoevenagel condensation which is a cross-aldol condensation of a carbonyl compound with an active methylene compound leading to C=C bond formation. This reaction has wide applications in the synthesis of fine chemicals and is classically catalyzed by bases in solution. This reaction can also be catalyzed by solid bases such as metal oxides. However, the water which is produced in the course of the reaction usually enters in adsorption competition with substrates, and thus acts as a poison.We herein report the fine tuning of hydrophobic properties of a MOF by post-synthetic modification in order to optimize its catalytic properties. Hydrophobic was characterized by water adsorption and surface tension measurements. To the best of our knowledge, we show for the first time that the engineering of the hydrophobic/hydrophilic environment can enhance the catalytic activity by an order of magnitude.
9:00 PM - UU9.16
Probing the Effects of Interpenetration and Open-metal Sites on the Uptake and Selectivity of Noble Gas Adsorption in Metal-organic Frameworks.
John Perry 1 , Scott Meek 1 , Patrick Feng 1 , Mark Allendorf 1
1 , Sandia National Laboratories, Livermore, California, United States
Show AbstractMetal-Organic Frameworks (MOFs) represent a burgeoning class of materials that are receiving a great deal of attention, largely due to their highly crystalline nature and potential applications. As they can often be obtained in a highly crystalline form, MOFs are uniquely well suited to act as platforms of materials useful for probing structure-property relationships. Additionally, MOFs often demonstrate permanent porosity and many of their most anticipated potential applications, such as gas storage (hydrogen storage and carbon dioxide sequestration for energy applications), chemical separations, chemical sensing, catalysis, and drug delivery involve the uptake or encapsulation of guests. Perhaps the most widely investigated application of MOFs to date has been gas storage, especially regarding hydrogen, carbon dioxide, methane, and more generically nitrogen. A fundamental understanding of adsorbent – adsorbate interactions for the nascent field of MOF materials has been elusive and would be greatly aided by empirical and corresponding theoretical studies concerning additional adsorbates, most notably noble gases. This presentation will outline recent experiments designed to evaluate a large assortment of MOFs for their ability to selectively adsorb noble gases. Particular attention will be given to MOF characteristics that have been shown to be important in the sorption of other gases, namely the total free-volume available, the presence of open-metal sites, and the effect of pore size through the influence of interpenetration. Furthermore, it is understood that for any MOF-based material to become truly practical in use, additional concerns must be addressed. In this vein, alternative synthetic methods designed to aid in scale-up to industrial levels will be discussed for the MOFs investigated. Finally, the viability of these materials as adsorbents over an extended lifetime will be addressed.
9:00 PM - UU9.17
Simulation of Low-pressure Noble Gas Adsorption in Nanoporous Framework Materials.
Stephanie Teich-McGoldrick 1 , Jeffery Greathouse 1 , Mark Allendorf 2
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , Sandia National Laboratories , Livermore, California, United States
Show AbstractDue to their extremely high surface areas but low density, nanoporous framework materials (NFM’s) are an important class of materials for gas storage and capture[1]. NFM’s are created from metal oxide centers connected by organic linkers, and with appropriate choice of building material NFM porosity and geometry can be tuned to preferentially adsorb and store gasses[2]. Specifically, we are interested in the adsorption of noble gases, which are present in the atmosphere in very low concentrations. We use grand canonical Monte Carlo simulations to determine the Henry’s constant, adsorption energies, and adsorption isotherms for noble gas and NFM systems at low pressures and room temperature. Simulations allow for the rapid screening of thousands of NFM’s and to predict the most favorable materials for noble gas storage and adsorption applications. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.1. Rowsell, J.L.C. and O.M. Yaghi, Metal-organic frameworks: a new class of porous materials. Microporous and Mesoporous Materials, 2004. 73(1-2): p. 3-14.2. Eddaoudi, M., et al., Systematic design of pore size and functionality in isoreticular MOFs and their application in methane storage. Science, 2002. 295: p. 469-472.
9:00 PM - UU9.18
Theoretical Binding Curves for Nanoscale Hydride Clusters.
Lucas Wagner 1 , Eric Majzoub 3 , Mark Allendorf 2 , Jeffrey Grossman 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Physics and Astronomy, University of Missouri, St. Louis, Missouri, United States, 2 , Sandia National Laboratories, Livermore, California, United States
Show AbstractMetal hydride materials are among the strongest contenders for hydrogen storage, offering good weight and volume density. The main reason that these materials are not used now is that it is very challenging to find a material that is both light enough and has the proper binding to allow for easy absorption/desorption near room temperature.We will evaluate two routes to controlling the binding energy: particle size and alloy composition. The two degrees of freedom can be explored experimentally using nanoporous materials, but it can be challenging to separate out size effects from surface effects and other confounding factors. We will present our work on generating benchmark-quality theoretical calculations of the binding energy as a function of size and alloy composition using the very accurate quantum Monte Carlo method. We find that traditional methods of calculating the binding energy such as the Wulff construction and density functional theory should be applied with caution, as they can lead to misleading results. We will also report on the prospects for finding a sweet spot of size and alloy composition that has the correct binding energy for hydrogen storage applications.
9:00 PM - UU9.3
Antimony-doped Highly Ordered Mesoporous SnO2 for Lithium-ion Battery Electrode.
Eun Byeol Hyeong 1 , Gwi Ok Park 1 , Ji Man Kim 1
1 Department of Chemistry and BK21 School of Chemical Materials Science, Department of Energy Science, and SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, Gyeonggi-do, Korea (the Republic of)
Show AbstractTin oxide is an attractive anode material as a potential substitute for the conventional graphite in lithium-ion batteries because the theoretical capacity of SnO2 (783 mAh/g) is higher than graphite (372 mAh/g). However, the practical use of SnO2 for anode material has several problems such as poor cycle ability resulting from severe volume changes and the poor electronic conductivity hinders the reaction with Li-ion during the first discharge. In order to enhance these drawbacks, we prepared antimony-doped highly ordered mesoporous SnO2 nanopowders by nano-replication method which is using silica template and simple reagents (SnCl4 and SbCl3) by impregnation. The synthesized mesoporous tin oxide with Ia3d meso-structure had high specific surface areas about 85-120 m2/g (calculated by BET equation) and pore size of ~18 nm (calculated by BJH equation). Synthesized samples were analyzed by powder X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron micrographs (TEM) and N2 adsorption-desorption isotherms. The prepared samples were tested as anode materials for lithium-ion batteries, whose charge-discharge properties, cyclic voltammetry, and cycle performance were examined.
9:00 PM - UU9.4
InfraSORB – A New Tool for High Throughput Adsorption Screening.
Stefan Kaskel 1 , Frieder Dreisbach 2 , Philipp Wollmann 1 , Matthias Leistner 3
1 , TU Dresden, Dresden Germany, 2 , Rubotherm, Bochum Germany, 3 , Fraunhofer Institute Materials and Beam Technology, Dresden Germany
Show AbstractIn recent years, the discovery of new materials such as Metal-Organic-Frameworks (MOFs), Element-Organic-Frameworks (EOFs), or Covalent-Organic-Frameworks (COFs) has led to novel benchmarks in terms of surface area and pore volume exceeding that of traditional adsorbents significantly [1-3]. Due to the wide parameter space in synthesis conditions and composition, high throughput synthesis and screening has been demonstrated to be an efficient tool for the discovery of new MOF structures [4-5]. Thereby, the development of high-throughput methods for the discovery of porous solids is crucial to speed up the discovery process. While diffraction and catalytic screening is nowadays an established technique, so far only a few instruments are available for rapid screening of specific surface area and porosity – for this application we present a new tool for fast screening of 12 samples within 5 minutes [6].The developed automated screening tool (infraSORB) is the last brick to skip the bottle-neck between high-throughput synthesis and measurement of adsorption capacities. Beside the investigation of new materials the instrument can also be used for product control. Enormous time benefits in connection with an easy-to-use interface and a sufficient accuracy are the advantages of the infraSORB instrument. The application of the instruments on different classes of porous materials such as zeolites, carbons, and MOFs will be presented.[1]Kitagawa et al.; Angew. Chem. (2004), (116), 2388-2430[2]Rose et al.; Chem. Comm. (2008), (21), 2462-2464[3]Masterlerz; Angew. Chem. Int. Ed. (2008), (47), 445-447[4]Biemmi et al.; Microp. Mesop. Mat. (2008), (117), 111-117[5]Plabst et al.; Cryst. Growth & Design (2009), (9), 5049-5060[6]S. Kaskel, P. Wollmann, M. Leistner; patent pending
9:00 PM - UU9.5
A Highly Porous Metal-organic Framework Based on a Ni5O2(O2CR)6 Secondary Building Unit.
Stefan Kaskel 1
1 , TU Dresden, Dresden Germany
Show AbstractWithin the growing field of MOF research the search for catalytically active materials and efficient adsorbents plays a key role. The presence of open metal centers within the framework is crucial in terms of a potential catalytic application3 but is also assumed to enhance the hydrogen storage capacities of MOFs.In the present contribution, we present the synthesis and characterization of a nickel based MOF with outstanding adsorption properties. The material, denoted as DUT-9 (DUT: Dresden University of Technology), is built of Ni5O26+ clusters interconnected by BTB linkers (BTB = 1,3,5-benzene tribenzoate) to form a three dimensional open framework structure exhibiting two types of pores approx. 13 Å and 25 Å in diameter arranged in an alternating fashion parallel to the c axis leading to the formation of channels. The material features a high concentration of open metal sites per cluster (Fig. 1) being occupied by coordinated solvent molecules (water, N,N-diethylformamide).Removing the guest molecules by conventional methods lead to destruction of the framework, thus, supercritical drying (SCD) turned out to be a suitable technique. An additional activation of the supercritically dried material at 120°C in vacuum lead to a partial removal of the coordinated solvent molecules which could not be achieved by SCD alone. As a result, a further increase of adsorption capacities is observed resulting in a pore volume of 2.18 cm3g-1, a hydrogen uptake of 5.85 wt.% (62 mg g-1) at 40 bar and a methane uptake of 219 mg g-1 at 100 bar. All values are among the highest reported for Metal-Organic Frameworks today and are in particular unique for nickel containing MOFs.
9:00 PM - UU9.7
II-VI Binary and II-II-VI Ternary Semiconductor Materials with Highly Ordered Mesostructures and Crystalline Frameworks.
Yoon Yun Lee 1 , Jeong Kuk Shon 1 2 , Seung Hwan Hong 1 , Ji Man Kim 1
1 Department of Chemistry and BK21 School of Chemical Materials Science, Department of Energy Science, and SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, Gyeonggi-do, Korea (the Republic of), 2 Energy Lab., Emerging Center, Samsung Advanced Institute of Technolgy (SAIT), Samsung Electronics Co., Ltd., Suwon, Gyeonggi-do, Korea (the Republic of)
Show AbstractRecently, II-VI semiconductor binary and ternary alloys have attracted a lot of attention because of their potential use in electronic and optoelectronic devices such as diode lasers, light-emitting diodes, photodetectors and photovoltaic devices operating in the ultraviolet-visible spectral range. The II-VI compound semiconductors are mostly characterized by a direct band gap with a range covering the entire visible spectrum from infra-red to ultraviolet. In addition, they are also characterized by bright emissions, which make them good candidates for application in photonic devices. Herein, we report on a facile synthetic route to highly ordered mesoporous II-VI binary and II-II-VI ternary compound semiconductor materials via nano-replication method using a ordered mesoporous silica (OMS) as a hard-template. The physicochemical properties of the replicated template-free semiconductor materials with high surface area and crystalline frameworks are characterized by using powder X-ray diffraction technique, nitrogen adsorption-desorption analysis, scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDS), ultraviolet-visible spectroscopy and photoluminescence analysis.
9:00 PM - UU9.8
Preparation of Highly Ordered Nanoporous Graphitic Carbon Nitride for Sensing Applications.
Gurudas Mane 1 2 , Toshiyuki Mori 3 2 , Vinu Ajayan 1 2
1 International Center for Materials Nanoarchitectonics, World Premier International (WPI) Research Center for Materials Nanoarchitectonics (MANA), National Institute of Material Science, Tsukuba, Ibaraki, Japan, 2 Graduate School of Science, Department of Chemistry, Hokkaido University, Sapporo -060-0810, Hokkaido, Japan, 3 Fuel Cell Materials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Ibaraki, Japan
Show AbstractCarbon Nitride materials have been of great interests to the scientific community because the incorporation of nitrogen atoms in the carbon nanostructures can enhance the mechanical, conducting, energy storage, adsorption and catalytic properties. In recent years much attention has been paid toward synthesis of graphitic carbon nitride which is the most stable allotrope of carbon nitride under ambient conditions. However, due to the high thermodynamic stability of carbon and N2 molecules, synthesis of carbon nitride with C3N4 stoichiometry and ordered mesoporosity is difficult to achieve. Recently, Vinu et al. reported the synthesis and characterization of one dimensional nanoporous carbon nitride materials with different pore diameters and surface areas. However, the nitrogen and the graphitic content of the materials are very low. In order to increase the nitrogen content and the graphitic nature of the materials, we have used aromatic precursors containing high nitrogen content, namely 3-Amino-1,2,4 triazine (3AT) as a nitrogen source. 3D nanoporous silica KIT-6 was used as a template. 3AT was effectively incorporated and polymerized inside the large pores of 3D-cubic KIT-6 silica template. The final highly ordered nanoporous graphitic carbon nitride with high nitrogen content was obtained by carbonizing the 3AT/KIT-6 silica composite followed by the removal of silica with HF. The obtained material (MCN-TN-x) has been unambiguously characterized by powder XRD, TEM, Nitrogen sorption measurements, EDX, FTIR and elemental analysis. The characterization results reveal that material possesses high specific surface area, large pore diameter, large pore volume and graphitic nature with average atomic C/N ratio value approaching the ideal stoichiometry and well ordered porous structure (Fig.1 and Fig.2). Interestingly, the nitrogen content of the materials is four times higher than the previously reported nanoporous carbon nitride. In addition, the sensing properties of the material were demonstrated by quartz crystal microbalance (QCM) measurement. The material showed a huge frequency shift for the acetic acid vapors as compared with the ethanol, ammonia, toluene and aniline vapors. Such a massive uptake of acetic acid vapors can be attributed to the combination of excellent textural properties and basic functionalities introduced by the nitrogen enrichment in carbon framework. This demonstrates that the above excellent material could be an excellent candidate for sensing toxic acidic molecules.
9:00 PM - UU9.9
Ordered Mesoporous SnO2 as Stable and High Capacity Anode Material for Lithium Ion Battery.
Gwi Ok Park 1 , Jeong Kuk Shon 1 2 , Hansu Kim 2 , Kiyoung Moon 1 , Eun Byeol Hyeong 1 , Ji Man Kim 1
1 Department of Chemistry and BK21 School of Chemical Materials Science, Department of Energy Science, and SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, Gyeonggi-do, Korea (the Republic of), 2 Energy Lab., Emerging Center, Samsung Advanced Institute of Technology (SAIT), Samsung Electronics Co., Ltd., Suwon, Gyeonggi-do, Korea (the Republic of)
Show AbstractLithium ion battery is considered the most promising energy storage technology for mobile electronics, electric vehicles and renewable energy system. Mesoporous anode material that consisted of particles containing nano-size pores separated by walls of similar size can deliver high rate power and high stability on cycling. In this report, we present simple and generic concept involving metal oxide with residual silica as stable and high capacity anode materials for Li ion battery. Specifically, highly ordered mesoporous SnO2 anode material with residual silica species for lithium ion battery was prepared using SBA-15 silica template via nano-replication and simple etching processes with various concentration of etching solution. Remaining silica species are in the range of 0.9–17.4 wt%, which induce a nano-propping effect enabling the mesoporous SnO2 material to remain stable up to 973 K without any significant structural collapse. More importantly, the optimum amount of residual silica species (3.9–6.0 wt%) results in a dramatic reduction in capacity fading after prolonged charging–discharging cycles. The observed, enhanced thermal stability with high capacity retention is derived from the residual silica species which acts as a physical barrier to prevent aggregation of Sn formed during the Li alloying and dealloying. The tools for this study included electron microscopy (SEM and TEM), XRD and standard electrochemical techniques.
Symposium Organizers
MarkD. Allendorf Sandia National Laboratories
Kendra McCoy Strategic Analysis, Inc.
A.Alec Talin National Institute of Standards and Technology
Stefan Kaskel Fraunhofer-Institute for Material and Beam Technology IWS
Symposium Support
Agilent Technologies UK Ltd
Defense Threat Reduction Agency (DTRA)
HORIBA Jobin Yvon, Inc.
National Institute of Standards and Technology
PANalytical
Quantachrome Instruments
Sandia National Laboratories
Sigma-Aldrich
Strategic Analys
UU10: Characterization Methods
Session Chairs
Thursday AM, April 28, 2011
Room 2024 (Moscone West)
9:30 AM - **UU10.1
Applications of Neutron Scattering to Understanding Structure and Gas Storage Properties of Metal-organic Frameworks and Related Materials.
Craig Brown 1 , Wendy Queen 1 , Matthew Hudson 1 2
1 Center for Neutron Research, NIST, Gaithersburg, Maryland, United States, 2 Material Science and Engineering, University of Maryland, College Park, Maryland, United States
Show AbstractThe development of nanostructured materials with predictable and controllable connectivity and functionalities has sparked a multitude of research directions. We have been studying emerging metal-organic framework (MOFs) systems and their adsorption properties for methane storage, carbon capture, gas separations but primarily hydrogen storage. Hydrogen storage materials must achieve higher gravimetric and volumetric densities than those of currently available in order to achieve a viable storage system that can be reversibly refueled. Although the storage capacities of MOFs have progressed significantly over recent years, some technological obstacles pose challenges for their future improvement. These include the generally low H2 adsorption enthalpy limiting room temperature applications and the lack of understanding of surface packing density hindering the efficient improvement of H2 adsorption uptake. The current approaches to achieving a viable material for hydrogen storage absorbents will be discussed. Neutron methods including powder diffraction, vibrational and rotational spectroscopy, and quasi-elastic scattering, are invaluable to advancing our understanding the performance (or lack of performance) of novel storage and adsorption systems. This will be illustrated by discussing several examples taken from our recent research involving both MOFs and nano-structured carbon-based materials.
10:00 AM - UU10.2
On the Porosity of Nanoporous Materials - From a Microscopic Point of View.
Nan Jiang 1
1 Physics, Arizona State Univ., Tempe, Arizona, United States
Show AbstractNanoporous materials have very unique properties that the corresponding bulk materials may not have, due to their high surface-to-volume ratio. One of important parameters characterizing porous materials is porosity, which is generally the ratio of void volume to solid volume. Here we introduce a new method to determine porosity of nanoporous materials, based on valence electron energy-loss spectroscopy (EELS). The method is based on effective medium dielectric theory. In inhomogeneous materials consisting of a fine scale mixture of different dielectric phases, the dielectric response is distinctively different than in the bulk materials, and can be replaced by effective medium response function ε(ω).This method was applied to nanoporous MgO, Al2O3, NiO, and TiO2. The bulk plasmon shifts are observed in all these nanoporous materials and the shift energy depend on the porosity. We successfully reproduced the experimental spectra by the effective medium dielectric theory and porosities were calculated using the fitting parameters. The results are consistent with measurements by small angle electron diffraction method.
10:15 AM - UU10.4
Szilard-Chalmers and X-ray Absorption Spectroscopy to Locate Copper Cations in Zeolite X.
Syed Khalid 1
1 Photon Science Directorate, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractSynthetic faujasites like Zeolites X and Y are important catalysts used in fossil energy for cracking and reforming. Position of cations in zeolites control their properties. Szilard-Chalmer Recoil studies and Neutron Activation Analysis was used to find the location of cations in Ba exchanged faujasites at different temperatures. We are using EXAFS as a complimentary technique to find the location of copper cations in a fully exchanged zeolite-X. The fully exchanged samples were calcined and then eluted with ammonium chloride to remove copper from open sites (super-cages). The remaining copper cations were in locked sites (sodalite-cages or hexagonal-prisms). Using X-ray Absorption Spectroscopy and the analysis of the first shell for co-ordination numbers, we will relate the position of cations at site I in the hexagonal-prism and site II in the sodalite-cages, adjacent to site I.
10:30 AM - UU10: CM
BREAK
UU12: Gas Storage
Session Chairs
Thursday PM, April 28, 2011
Room 2024 (Moscone West)
2:30 PM - UU12.1
Mesoporous Metal-organic Frameworks for Gas Storage and Enantioselective Catalysis.
Stefan Kaskel 1
1 , TU Dresden, Dresden Germany
Show AbstractFor the separation or conversion of larger molecules in porous systems, well defined mesoporous catalysts are needed. Recently significant progress was made in the area of mesoporous MOFs. DUT-6 (Zn4O(2,6-NDC)(BTB)4/3) [1], is a novel MOF system with a specific pore volume > 2 cm3/g and is therefore suited in gas storage applications, especially with regard to hydrogen, methane and n-butane uptake. Here the mixed ligand linker approach was successful and BTB generated large pores of dodecahedral cages. A novel system composed of Ni5-clusters was obtained with even larger pore volume (DUT-9)[2] and an umprecedented motif exposing nickel sites. A new approach to the synthesis of chiral Metal-Organic Frameworks was developed by substitution of the BTB linker by chiral oxazolidinone subunits (H3ChirBTB-n). The materials obtained with zinc nitrate, Zn3(ChirBTB-n)2, show different framework structures depending on the nature of the chiral substituent. Using copper as metal for framework formation, materials with similar crystal structures were obtained being analogous to that of Zn3(ChirBTB-1)2. Application of the ChirBTB-MOFs in Mukaiyama aldol reaction lead to an enantiomeric excess of the formed product [3].[1] Klein, N.; Senkovska, I.; Gedrich, K.; Stoeck, U.; Henschel, A.; Mueller, U.; Kaskel, S. Angew. Chem. Int. Ed. 2009, 48, 9954.[2] K. Gedrich, I. Senkovska, N. Klein, U. Stöck, A. Henschel, M. Lohe, I. Baburin, U. Müller, S. Kaskel, Angewandte Chemie 2010, DOI: 10.1002/anie.201001735.[3] Heitbaum, M.; Gedrich, K.; Notzon, A.; Senkovska, I.; Fröhlich, R.; Getzschmann, J.; Mueller, U.; Glorius, F.; Kaskel, S. Chem. Eur. J. accepted.
2:45 PM - UU12.2
Volatile Gas Adsorption in Metal-organic Frameworks (MOFs).
Dorina Sava 1 , Mark Rodriguez 2 , Karena Chapman 3 , Gregory Halder 3 , Peter Chupas 3 , Tina Nenoff 1
1 Surface & Interface Sciences, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Materials Characterization, Sandia National Laboratories, Albuquerque, New Mexico, United States, 3 X-ray Science Division, Advanced Photon Source, Argonne National Laboratories, Argonne, Illinois, United States
Show AbstractInteractions occurring at the molecular level between adsorbed volatile gases and porous hosts proffer very useful information for the design of made-to-order materials. Here, we investigate fundamental studies aimed to understand the nature of the chemical environment of adsorbed molecular iodine within metal-organic frameworks (MOFs). Emphasis is placed on identifying key structural features that play an important role for efficient and highly selective iodine retention.The adsorption of volatile gases resulted during nuclear fuel reprocessing represents an ongoing challenge. In spite of not being a major component of the off-gas resulted during this process, radioiodine is particularly challenging as it is a long-lived radionuclide (16 million years), it is mobile and it is known to cause metabolic reactions in humans. Therefore, its capture and sequestration is of great interest on a societal level. In this context, our studies align with current investigations that utilize solid-state porous materials, such as silver-exchanged zeolites as benchmark compounds for iodine trapping. Additionally, we further extend the endeavor to capture volatile gases of interest onto highly porous and tunable MOFs.Experiments include the synthesis and characterization of both commercially available and novel synthesized frameworks, and the structure-property relationship between the framework and its ability to sorb iodine. Results indicate that activated MOFs sorb iodine in larger amount from both solution and vapor phase. Information concerning the adsorbate-adsorbent interactions was obtained performing structure refinement from powder X-ray diffraction on the as-loaded compounds using the Rietveld method. Thus, it was confirmed that iodine is present in its molecular form inside the pores, finding that was further reinforced by differential pair distribution function (d-PDF) studies. Preliminary results indicate that molecular iodine occupancy increases with increased loadings, while values obtained for the intramolecular iodine distances fall within the expected ranges. Complementary characterization techniques, such as SEM-EDS analysis, and TGA-MS have also been employed to depict the profile of the iodine-loaded compounds.Future work is directed towards identifying the structure-function relationships in these systems, which will further facilitate the engineering of novel materials that will selectively adsorb iodine-containing species (I2, HI, HIO3 and CH3I) from complex streams. *Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
3:00 PM - UU12.3
Some New Flexible Gate Pressure MOFs.
Stefan Kaskel 1 , Irena Senkovska 1 , Eike Brunner 1
1 , TU Dresden, Dresden Germany
Show AbstractIn contrast to traditional porous solids such as zeolites or activated carbons, MOFs do show gas pressure dependant crystal-to-crystal transformations associated with pore opening and closing (gate pressure effect).Recently DUT-8 (Ni2(ndc)2dabco) was obtained as a new gate pressure MOF with high surface area (2000 m2/g) after gate opening. The system shows a gate effect for gases such as N2, Xenon, and Butane. The gate opening is not only visible in the isotherm but also monitored using Xe NMR. Furthermore, an extended tetracarboxylate afforded a new Zn-MOF (DUT-13) also showing flexibility. The impact of the supercritical state on the adsorption isotherm will be analysed.
3:15 PM - UU12.4
MOFs as Templates for Nanoscale Metal Hydrides: Implications on the Thermal Properties.
Raghunandan Bhakta 1 , Aaron Highley 1 , Rich Behrens 1 , Vitalie Stavila 1 , Mark Allendorf 1 , Lucas Wagner 2 , Jeffrey Grossman 2
1 Energy Nano Materials, Sandia National Laboratories, Livermore, California, United States, 2 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractHydrogen storage is under intense investigation because of the challenging technical barriers in the implementation of a hydrogen-based energy economy. Lightweight metal hydrides are often considered as good storage media, but are limited by their kinetic constraints. An alternative approach to address this issue is to reduce the particle size of the metal hydride to the nanometer range, resulting in enhanced kinetics without the need of a catalyst. The objective of this work is to use metal organic frameworks (MOFs) as templates for the synthesis of nano-scale metal hydride particles, and to determine quantitative differences from corresponding bulk properties. LiH has the highest hydrogen content of any metal hydrides. Since LiH is not sufficiently soluble to be infiltrated into template pores by solution methods, commercially available LiC2H5 solutions (~ 0.5M) were used to introduce Li to the pores. Heating the infiltrated MOF template (CuBTC in this case) to 200 C under reduced pressure for 16 hours creates LiH by beta hydride elimination. The presence of the hydride is clearly evident from the infrared spectrum, although according to elemental analysis the loading is very light. TEM/electron energy loss spectroscopy confirms the presence of Li uniformly throughout the template crystals, indicating that the Li is within the pores. On average, there are only three LiH formula units for every two of the large pores in the CuBTC template. This light loading provides an opportunity to compare the hydrogen desorption kinetics of extremely small LiH clusters with the predictions of theoretical models. The Wulff construction model predicts that (LiH)n becomes increasingly stable as n decreases, while the QMC calculations predict little variation from the bulk until n = 1 or 2, at which point the hydride is destabilized relative to the bulk. MOf infiltrated LiH nanoparticles did not show any destabilization effect relative to bulk, consistent with quantum Monte Carlo predictions (QMC). In order to analyze the solid state reaction of hydrogen desorption from the NaAlH4@CuBTC, experiments were carried out using isothermal steps in the temperature range of 50-200°C. Two desorption regions are observed, the first one during the heating up to 180 C, and the other during the cooling off period. The rate of H2 release during the cooling portion of the first cycle is much less than is observed in the heating portion. This may indicate absence of an equilibrium type of process. Analyses were carried out using 16 different types of solid state reaction models. Preliminary results show that the activation energy for hydrogen desorption from NaAlH4@CuBTC varies from 50.1- 94.6 kJ/mol by applying two different models.The present work demonstrates that MOFs are stable hosts for metal hydrides and their reactive precursors and those can be used as templates to form metal hydride nanoclusters on the scale of their pores (1 – 2 nm).
3:30 PM - UU12.5
Probing Host-guest Interactions Involving a Hydrophobic Metal-organic Framework and a Variety of Gas and Solvent Vapor Adsorbates.
Chi Yang 1 , Nour Nijem 2 , Kui Tan 2 , Augustin Venero 3 , Ushasree Kaipa 1 , Ecatherina Roodenko 2 , Yves Chabal 2 , Mohammad Omary 1
1 Department of Chemistry, University of North Texas, Denton, Texas, United States, 2 Material Science and Engineering, University of Texas at Dallas, Dallas, Texas, United States, 3 , VTI Corporation, Hialeah, Florida, United States
Show AbstractFluorinated metal-organic frameworks (FMOFs) is a new class of porous materials exhibiting fluoro-coated cavities that bestow unusual stability, high volumetric gas adsorption capacity, and gigantic negative and positive thermal expansion with record-breaking breathing capabilities (Yang et al. JACS 2007; Angew Chem. 2009). Here we report that the hydrophobic cavities of the FMOFs render high water stability compared to conventional MOFs and very little water adsorption compared to zeolites and BPL carbon. Furthermore, we show enhanced adsorption of aromatic and aliphatic hydrocarbons (with enhanced selectivity for the former) as well as CO2 into FMOF-1 when a small amount of water is absorbed into its smaller cavities. FMOF-1 consists of semi-rectangular fluoro-lined microporous channels (~ 12.2 Å) along with diamond-shaped nanoporous cages (~4 Å). Other crystal polymorphs with larger and smaller channels and/or cages have also been isolated and characterized crystallographically. Our work illustrates remarkable uptake by the FMOFs for various guest molecules, including hydrogen, oxygen, nitrogen, carbon dioxide, methane, hexane isomers, benzene, toluene, xylene isomers, and hazardous industrial gases. The focus of this presentation will be competitive uptake of such guests in presence of water so as to simulate practical conditions to encounter the potential use of FMOFs in various transportation and environmental-related applications. We will show multiple crystal structures of FMOFs trapping many of the aforementioned guests as obtained by crystallization from non-dry solvents, gas and solvent sorption isotherms (including water vapor for FMOF-1 vs. zeolites and BPL carbon), and results of in-situ vibrational spectra (IR and Raman). The latter are used as probing techniques to study the influence of water on the adsorption of methane, CO2 and H2 in order to identify their different adsorption sites in FMOF-1. The existence of small traces of water in the H2 gas could be identified by the appearance of an IR band at ~3683 cm-1 that is attributed to isolated OH bands. H2 and CO2 adsorption show a hysteresis that has been verified by both IR and isotherm measurements. The adsorption of minute amounts of water into the small pores will be discussed as a possible reason for this hysteresis, as unraveled by both IR spectroscopy and Powder X-ray Diffraction (PXRD) measurements. PXRD results show that the FMOF-1 structure retains its crystallinity after water adsorption. Isotherm, IR, and PXRD data will be intercorrelated to illustrate framework expansion upon multiple cycles of high-pressure adsorption.
4:15 PM - UU12.6
Molecular Modeling of the Structure, Thermodynamics and Kinetics of Gas Adsorption in Zeolitic Imidazolate Frameworks (ZIFs).
Brian Laird 1 , Ning He 1 , Mark Asta 2 , David Olmsted 2 , Yao Houndonougbo 3
1 Chemistry, University of Kansas, Lawrence, Kansas, United States, 2 Materials Science and Engineering, University of California, Berkeley, California, United States, 3 Chemsitry, University of Eastern Washington, Cheney, Washington, United States
Show AbstractWe present the results of a series of Monte Carlo and Molecular Dynamics simulations of carbon dioxide, methane and nitrogen uptake in several zeolitic imidazolate frameworks (ZIFs) . In this talk we focus primarily on an isoreticular series of ZIFs with a RHO structure is examined to understand the role of ZIF functionalization on the structure, thermodynamics and kinetics of gas adsorption at fixed ZIF topology. Using standard off-the-shelf potentials, we obtain good agreement between simulation and experimental adsorption results and that the adsorption is strongly dependent on the polarizability and symmetry of the imidazolate functionalization. Adsorption is seen to occur preferentially into the hexagonal bridging channels of the RHO structure over the octahedral pore.
4:30 PM - UU12.7
Exploring the Effects of Chemical Functionality on the Interactions Between Noble Gases and Metal-organic Frameworks.
Scott Meek 1 , John Perry 1 , Patrick Feng 1 , Mark Allendorf 1
1 , Sandia National Laboratories, Livermore, California, United States
Show AbstractWith applications ranging from lighting, lasers and analgesics to window insulation and detection of underground nuclear explosions, noble gases represent a very useful class of compounds. As these gases, especially krypton and xenon, can be quite rare and expensive, materials for capturing, separating and concentrating noble gases are highly desirable. Metal-organic frameworks (MOFs), hybrid lattices of metal ions and organic electron donors, have enjoyed extensive study in the fields of gas storage and separation. However, few reports investigate the adsorption of the noble gases by these materials. In particular, the role of chemical functionality in tuning noble gas-MOF interactions has not been extensively explored. We have prepared a series of IRMOF-1 derivatives with various monosubstituted terephthalic acids, including functional groups –H (IRMOF-1), -NH2 (IRMOF-3), -Br (IRMOF-2), -I, -Cl, and –F. We will present noble gas adsorption isotherms for these materials from 0-1 atm and at near ambient temperatures. The effects of chemical functionality, surface area, and pore size on overall uptake, heats of adsorption, and gas selectivity will be discussed. Additionally, we will report the effects of various activation methods, including solvent exchange and supercritical CO2 drying, on the structural and noble gas adsorption properties of these MOFs.
4:45 PM - UU12.8
Hydrogen Storage in Metal-organic Frameworks.
Kenji Sumida 1 2 , Hye Jin Choi 1 2 , Zoey Herm 1 2 , Jeffrey Long 1 2
1 Department of Chemistry, University of California, Berkeley, Berkeley, California, United States, 2 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractMaterials exhibiting reversible hydrogen adsorption with high gravimetric and volumetric capacities are sought for use in on-board storage systems of hydrogen fuel cell-powered vehicles. Microporous metal-organic frameworks with high internal surface areas have been shown to display excellent storage properties, but only at cryogenic temperatures. Methods for synthesizing frameworks containing coordinatively-unsaturated metal centers are therefore being developed as a means of increasing the H2 adsorption enthalpy. In particular, we seek to synthesize thermally-robust, high-surface area materials with a high concentration of open metal coordination sites. By adjusting the electronic structure of the metal ions, it is expected that an optimal H2 binding enthalpy in the range 15-20 kJ/mol can be achieved, leading to a high H2 storage capacity at room temperature and safe pressures of up to 100 bar. Our approaches involve the insertion and activation of metal carbonyl units on the aromatic components of existing frameworks, as well as the design of new frameworks using bridging ligands that facilitate the generation of open metal coordination sites.
5:00 PM - UU12.9
First-principles Calculations on Hydrogen Storage Capacity.
Hiroshi Mizuseki 1 , Natarajan Venkataramanan 1 , Ryoij Sahara 1 , Yoshiyuki Kawazoe 1
1 , Institute for Materials Research, Tohoku Univ., Sendai, Miyagi, Japan
Show AbstractDoping with alkali metal elements increases the hydrogen storage capacity of many materials. Inspired by these findings, we have explored the hydrogen storage properties of lithium doped Metal Organic Frameworks (MOFs) and BN fullerenes. Binding energy of alkali atoms on BN fullerenes were identical to C60. However, the binding on BN fullerene occurs at the bridge site near the tetragonal site. Alkali adsorption can be adsorbed to a maximum of six sites. Each Li atom was found to hold up to 3 hydrogen molecules. Ab initio MD studies shows that these materials have working temperature between 200K and 300K. In the case of the MOF materials, Li-doping significantly improves the hydrogen uptake. Each Li atom doped was found to hold three H2 molecules firmly due to the charge induced dipole interaction. The most stable position for the Li atom was found to be on the benzene ring, forming a Li-benzene complex and each benzene ring was able to hold two Li atoms [1]. The pure organic compound, p-tert-butyl calixarene (TBC), has the capability to store up to 0.6 wt.% of hydrogen. TBC was found to hold one H2 molecules inside its cavity, whereas Li-functionalized TBC was able to hold 4 H2 molecules inside its cavity. The mean distance between the Li and hydrogen molecules increases with the increasing number of hydrogen molecules, while the fourth H2 molecule exists at a nonbonding distance of 4.19 Å from the Li atom and was inside the cavity. Ab initio molecular dynamic studies show that Li - functionalized TBC is stable up to 200K while hydrogen incorporated material was stable up to 100K [2, 3]. A part of this work has been supported by New Energy and Industrial Technology Development Organization (NEDO) under “Advanced Fundamental Research Project on Hydrogen Storage Materials”. 1) N. S. Venkataramanan, R. Sahara, H. Mizuseki, and Y. Kawazoe, Int. J. Mol. Sci. 10, 1601 (2009). 2) N. S. Venkataramanan, R. Sahara, H. Mizuseki, and Y. Kawazoe, J. Phys. Chem. C. 112, 19676 (2008).3) N. S. Venkataramanan, R. Sahara, H. Mizuseki, and Y. Kawazoe, Comput. Mater. Sci., 49 (2010) S263-S267.
5:15 PM - UU12.10
Concentration-driven Enhancement of Hydrogen Storage Capacity of MOF-5s.
Seung Jae Yang 1 , Jung Hyun Cho 1 , Chong Rae Park 1
1 Department of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractThe development of a viable hydrogen storage system is crucial step for realization of hydrogen fuelled automobiles. Among a variety of materials such as carbon nanotubes, zeolites, complex metal hydrides and metal-organic framework (MOF), MOFs have been considered as an effective hydrogen storage adsorbent. But there has been little systematic information available on the effect of synthetic parameters on the evolution of structural features such as crystal structure and pore characteristics and further on hydrogen storage capacity of MOFs. We therefore carried out a systematic study to find the effects of the synthetic conditions on the evolution of crystal structure, pore characteristics, and hydrogen storage capacities of MOF-5s through both experimental and computational studies. We found that the precursor concentration had a noticeable influence on the degree of interweaving in the MOF-5s: high concentrations favored interwoven crystal forms, whereas low concentrations favored non-interwoven crystal forms. This variation has led to a substantial difference in the pore characteristics. Since the interweaving reduced pore volume and constricted pore dimensions, the Langmuir specific surface areas of the MOF-5s were significantly decreased from 2696 to 1006 m2/g, with concurrent evolution of ultramicroporosity. Moreover, the changes in the pore characteristics have affected the hydrogen storage capacities of the product. Cryogenic hydrogen storage capacity (77 K) at 1 bar of the interwoven MOF-5s was enhanced from 1.03 wt% (non-interwoven MOF-5) to 1.76 wt% due to highly developed ultramicroporosity. Our results indicate that this simple but efficient concentration controlled synthesis method not only provides highly interwoven and/or non-interwoven MOF-5s, but also allows a control of the pore characteristics and H2 storage capacity of MOF-type materials. The understanding of this correlation is particularly useful to establish favorable synthetic criteria for the preparation of MOF-type materials with rational designs.