Grand canonical Monte Carlo (GCMC) simulations of H2 sorption were performed in rht-MOF-1, a metal–organic framework (MOF) with rht topology that consists of Cu2+ ions coordinated to 5-tetrazolylisophthalate ligands. rht-MOF-1 is a highly charged and polar MOF through the presence of two types of open Cu2+ ion sites (via the [Cu2(O2CR)4] and [Cu3O(N4CR)3] units) and extra-framework NO3– counterions. The simulations were performed using four different H2 potentials of increasing complexity, with the most realistic potential including induced dipole parameters to account for explicit many-body polarization interactions. Explicit polarization effects were implemented in classical GCMC simulation using a Thole-Applequist type model. Experimental observables for rht-MOF-1, such as the H2 sorption isotherms at 77 and 87 K for pressures up to 1 atm and the isosteric heat of adsorption (Qst) values, were closely reproduced in simulation using only the polarizable H2 potential. Simulations using potentials that include only explicit repulsion and dispersion and/or permanent electrostatic interactions failed to reproduce such measurements. Further, simulations using only the polarizable H2 potential revealed a significant quantity of H2 molecules sorbed onto both types of open metal-sites in the MOF, with short and accurate Cu2+–H2 distances. In addition, simulations involving explicit many-body polarization interactions assisted in the determination of the binding sites in rht-MOF-1 through the distribution of the induced dipoles.

Importance of polarization in simulations of H2 sorption in rht-MOF-1

251st National Meeting (2016)

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