High-Temperature Hydrogen Storage of Multiple Molecules: Theoretical Insights from Metalated Catechols

Insertion of open metal sites (OMS) into metal-organic frameworks (MOFs) is a promising strategy for preparation of physical adsorbents that enable H-2 storage at room temperature. Density functional theory (DFT) calculations are reported on a promising paradigm for adsorption of multiple hydrogen molecules to a single OMS attached to an MOF linker via a catechol or thiocatechol. The interactions between adsorbed H-2 and the OMS are characterized with special attention to their degrees of freedom and thermal properties. By combining the present calculations with experimental data, some of these materials are predicted to have usable capacities close to the Department of Energy (DOE) 2020 target of 40grL(-1) marking them as important synthetic targets. Surprisingly, calculations suggest that a Ca-catechol OMS retains the ability to bind up to two hydrogens even in the presence of residual solvent.