Simulation of the Mechanism of Gas Sorption in a Metal–Organic Framework with Open Metal Sites: Molecular Hydrogen in PCN-61

Abstract

Grand canonical Monte Carlo (GCMC) simulations were performed to investigate hydrogen sorption in an rht-type metal–organic framework (MOF), PCN-61. The MOF was shown to have a large hydrogen uptake, and this was studied using three different hydrogen potentials, effective for bulk hydrogen, but of varying sophistication: a model that includes only repulsion/dispersion parameters, one augmented with charge-quadrupole interactions, and one supplemented with many-body polarization interactions. Calculated hydrogen uptake isotherms and isosteric heats of adsorption, Qst, were in quantitative agreement with experiment only for the model with explicit polarization. This success in reproducing empirical measurements suggests that modeling MOFs that have open metal sites is feasible, though it is often not considered to be well described via a classical potential function; here it is shown that such systems may be accurately described by explicitly including polarization effects in an otherwise traditional empir...