An Ab Initio Force Field for Predicting Hydrogen Storage in IRMOF Materials

An ab initio force field that describes interactions between hydrogen molecules and IRMOF materials is proposed. The force field parameters were derived by fitting to ab initio data that includes higher-order electron correction and extended basis-set effects and validated by calculating adsorption isotherms and isosteric heats of adsorption of H2 in IRMOF-1 using GCMC simulations performed at 77 and 298 K, in a broad range of pressure from 0.0 to 8.0 MPa. Excellent agreements with experimental data were obtained. The force field was then applied to predict hydrogen-storage capacities for eight additional IRMOF materials. It was identified that the void fraction of volume (VFV) has a strong impact on the adsorption capacity, and its impacts on gravimetric and volumetric adsorption uptakes exhibit opposite trends. An overall optimal VFV is ca. 87% for IRMOFs at 77 K and 8.0 MPa.