Effects of structure on hydrogen adsorption in zeolitic imidazolate frameworks

Grand canonical Monte Carlo (GCMC) simulations were employed to compute the adsorption of hydrogen gas in zeolitic imidazolate frameworks (ZIF-1, ZIF-2, ZIF-3, ZIF-4, ZIF-6, ZIF-10 and ZIF-64). In this set of ZIFs, all of them have the same metal atoms and ligands, but they have different structures. A reasonable relationship between the saturated adsorption of ZIFs and their effective porosities is established. Further, this linear relationship was used to predict the saturated adsorption amounts of ZIFs with the same metal atoms and ligands. In addition, by comparing the different structural forms it is found that the hydrogen uptake of ZIFs is mainly controlled by their structure; the order is Tetragonal>Orthorhombic>Monoclinic, and with the same crystal system, the body-centered lattice (I) is better than the simple lattice (P). These results would be helpful for designing and synthesizing new ZIFs with improved hydrogen uptake capability.

► A linear relationship between the hydrogen adsorption and the effective porosity.
► Prediction of the ZIFs’ hydrogen adsorption with the same metal atoms and ligands.
► The hydrogen uptakes of ZIFs in order of Tetragonal>Orthorhombic>Monoclinic.
► The same crystal system, the body-centered lattice better than the simple lattice.