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

Jonathan L. Belof, Abraham C. Stern, Mohamed Eddaoudi, and Brian Space*
Contribution from the Department of Chemistry, University of South Florida, 4202 East Fowler Avenue, CHE205, Tampa, Florida 33620-5250
J. Am. Chem. Soc., 2007, 129 (49), pp 15202–15210
DOI: 10.1021/ja0737164
Publication Date (Web): November 14, 2007
Copyright © 2007 American Chemical Society

Abstract

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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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History

  • Published In Issue December 12, 2007
  • Received June 11, 2007

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