Insights on the physical adsorption of hydrogen and methane in UiO series of MOFs using molecular simulations

Abstract

Molecular simulations were used to study the single component adsorption of H2 and CH4 in the iso-structural MOFs UiO-66, UiO-67 and UiO-68. The energetic landscape and the adsorption sites for the two gases are analyzed in detail while the pure component adsorption results are discussed in terms of excess adsorption capacities and isosteric heats, highlighting the limitations of the UiO pore topology for the adsorptive storage of H2 and CH4. It is shown that adsorption occurs primarily due to the interactions between the linker and the guest molecules.We furthermore analyze the performance of the UiO series for H2 and CH4 storage either at 77K or at 298K. At 77K the unique topology of the UiO structures enhances the fluid–solid interactions and it is shown that the excess H2 adsorption capacity of UiO-66, at 1bar as well as the maximum adsorption excess of UiO-68 surpass most of the known MOF structures (including MOF-7, MOF-177 and HKUST1). On the other hand at room temperature the theoretical adsorption limit of these MOFs for both H2 and CH4 is rather moderate.