Hydrogen Storage in a Prototypical Zeolitic Imidazolate Framework-8

William Penn University, Filadelfia, Pennsylvania, United States
Journal of the American Chemical Society (Impact Factor: 12.11). 05/2007; 129(17):5314-5. DOI: 10.1021/ja0691932
Source: PubMed


Using the difference Fourier analysis of neutron powder diffraction data along with first-principles calculations, we reveal detailed structural information such as methyl group orientation, hydrogen adsorption sites, and binding energies within the nanopore structure of ZIF8 (Zn(MeIM)(2)). Surprisingly, the two strongest adsorption sites that we identified are both directly associated with the organic linkers, instead of the ZnN4 clusters, in strong contrast to classical MOFs, where the metal-oxide clusters are the primary adsorption sites. These observations are important and hold the key to optimizing this new class of ZIF materials for practical hydrogen storage applications. Finally, at high concentration H-2-loadings, ZIF8 structure is capable of holding up to 28 H-2 molecules (i.e., 4.2 wt %) in the form of highly symmetric novel three-dimensional interlinked H-2-nanoclusters with relatively short H-2-H-2 distances compared to solid H-2. Hence, ZIF compounds with robust chemical stability can be also an ideal template host-material to generate molecular nanostructures with novel properties.

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    • "The composition and formulation of the filler and matrix of MMM materials are important aspects of achieving superior gas separation performance. A variety of polymer matrices have been employed, including: polyimides [20] [21], super glassy polymers [22], cross-linkable polymers [23] [24] [25] [26] [27], amphiphilic graft copolymers [28] [29] [30] and block copolymers [31] [32]. In particular, block copolymers are a promising matrix due to the elaborate microphase-separated structures that are possible with these materials, enabling a synergistic effect of high gas permeation properties and mechanical strength. "
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    • "In particular, zeolitic imidazolate frameworks (ZIFs) are a subclass of metal organic frameworks with zeolite or zeolitelike topologies, which possess several extraordinary features, such as chemical robustness and thermal stability [7] [8]. Among various ZIFs materials, ZIF-8 which is a tetrahedral framework formed by zinc ions and imidazolate ligands with sodalite topology is the most extensively studied [9]. Substantial works have been done on synthesizing ZIF-8 for gas sorption/separation, catalysis, electrochemical biosensor, as well as functionalized thin films, etc. [10] [11] [12] [13] [14]. "
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    • ", Covalent Triazine based Frameworks (CTFs) [10] and Zeolitic Imidazolate Frameworks (ZIFs) [11] are promising candidates as hydrogen storage materials. This is due to their great number of hydrogen adsorption sites, tunable pore sizes to trap hydrogen molecules on the host material's surface and ease of hydrogen adsorption/desorption from the host materials . "
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