On the Mechanism of Hydrogen Storage in a Metal−Organic Framework Material

Department of Chemistry, University of South Florida, Tampa, Florida, United States
Journal of the American Chemical Society (Impact Factor: 12.11). 01/2008; 129(49):15202-10. DOI: 10.1021/ja0737164
Source: PubMed


Monte Carlo simulations were performed modeling hydrogen sorption in a recently synthesized metal-organic framework material (MOF) that exhibits large molecular hydrogen uptake capacity. The MOF is remarkable because at 78 K and 1.0 atm it sorbs hydrogen at a density near that of liquid hydrogen (at 20 K and 1.0 atm) when considering H2 density in the pores. Unlike most other MOFs that have been investigated for hydrogen storage, it has a highly ionic framework and many relatively small channels. The simulations demonstrate that it is both of these physical characteristics that lead to relatively strong hydrogen interactions in the MOF and ultimately large hydrogen uptake. Microscopically, hydrogen interacts with the MOF via three principle attractive potential energy contributions: Van der Waals, charge-quadrupole, and induction. Previous simulations of hydrogen storage in MOFs and other materials have not focused on the role of polarization effects, but they are demonstrated here to be the dominant contribution to hydrogen physisorption. Indeed, polarization interactions in the MOF lead to two distinct populations of dipolar hydrogen that are identified from the simulations that should be experimentally discernible using, for example, Raman spectroscopy. Since polarization interactions are significantly enhanced by the presence of a charged framework with narrow pores, MOFs are excellent hydrogen storage candidates.

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    • "The simulations have great concurrency with the experimental results, which mainly depend on the calculation algorithms and methods. Molecular simulation calculations used to understand mechanism of hydrogen storage in MOF material by Belof and co-workers [32]. That the main approach was Grand Canonical Monte Carlo ensemble (GCMC) which was described by Vlanchy et al. [33]. "

    Full-text · Article · Nov 2015
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    • "However, significant hydrogen adsorptive storage capacities in physisorption need to be reached at liquid-nitrogen temperatures (77 K) and pressures of several MPa. This is attributed to weak binding energy between molecular hydrogen and the surface of sorbents in the range of 2–5 kJ mol À 1 H 2 [8] [9] [10] [11] [12]. Generally, the hydrogen storage properties of physisorption appear to be limited by specific surface area (SSA), pore structures and pore size distributions, surface functionality and the bulk density of the adsorbents. "
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    • "O(abtc) 3/2 (NO 3 ), also termed soc-MOF – indicates that electrostatic interactions and induction effects play an important role for these special cases [27] "
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    ABSTRACT: The capabilities and limitations of the application of molecular simulation techniques to the adsorption of hydrogen in metal-organic frameworks (MOFs) are explored for selected case studies. Force field based grand-canonical Monte Carlo simulations are employed to investigate the adsorption characteristics of three different isoreticular MOFs, resulting in good agreement with experimental findings. The predictive potential of the method is demonstrated for Zn4O(mip)3, a novel system which has not yet been fully characterized experimentally. Further calculations for MOFs with unsaturated metal sites reveal a shortcoming of the simulation technique, as the interaction of hydrogen with these sites is not adequately represented by the potential model. Density functional theory calculations are employed to study the metal–dihydrogen interaction in more detail, making use of a non-periodic model system which is representative for many copper-containing MOFs.
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