Computational study of hydrogen binding by metal-organic framework-5.

We report the results of quantum chemistry calculations on H(2) binding by the metal-organic framework-5 (MOF)-5. Density functional theory calculations were used to calculate the atomic positions, lattice constant, and effective atomic charges from the electrostatic potential for the MOF-5 crystal structure. Second-order Møller-Plesset perturbation theory was used to calculate the binding energy of H(2) to benzene and H(2)-1,4-benzenedicarboxylate-H(2). To achieve the necessary accuracy, the large Dunning basis sets aug-cc-pVTZ, and aug-cc-pVQZ were used, and the results were extrapolated to the basis set limit. The binding energy results were 4.77 kJ/mol for benzene, 5.27 kJ/mol for H(2)-1,4-benzenedicarboxylate-H(2). We also estimate binding of 5.38 kJ/mol for Li-1,4-benzenedicarboxylate-Li and 6.86 kJ/mol at the zinc oxide corners using second-order Møller-Plesset perturbation theory. In order to compare our theoretical calculations to the experimental hydrogen storage results, grand canonical Monte Carlo calculations were performed. The Monte Carlo simulations identify a high energy binding site at the corners that quickly saturated with 1.27 H(2) molecules at 78 K. At 300 K, a broad range of binding sites are observed. (c) 2004 American Institute of Physics.