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 Moller-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 Moller-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.