A computational approach towards understanding hydrogen gas adsorption in Co-MIL-88A

Unsaturated metal centers in metal-organic framework MIL-88A are able to significantly enhance the amount of gas adsorbed at ambient temperatures and low pressures. This material has been investigated for various applications; however, it has not yet been tested for hydrogen storage. In this research, we examined the interaction of hydrogen gas (H-2) with Co-MIL-88A by using the van der Waals dispersion-corrected density functional theory calculations. The H-2 molecule was found to adsorb most favorably at the hollow site of the metal trimers in Co-MIL-88A because of the maximum overlap between the bonding state of the H-2 molecule and the total density of state of the Co-MIL-88A. In addition, the hydrogen adsorption isotherms were also assessed by grand canonical Monte Carlo simulations. The results showed that Co-MIL-88A is one of the most effective H-2 storage materials.