Molecular dynamics simulation study on the hydrogen adsorption and diffusion in non-interpenetrating and interpenetrating IRMOFs

We performed molecular dynamics simulations at 77 K on the non-interpenetrating isoreticular (having the same underlying topology) metal-organic frameworks (IRMOFs) and the interpenetrating IRMOFs to investigate the adsorption behavior of hydrogen on the surface of MOFs, catenation effect on the density of adsorbed hydrogen, and dynamic behavior of adsorbed hydrogen molecules. We tested two classical force fields, universal force field (UFF) and DREIDING force field for the simulations and found out that the UFF describes the adsorption of hydrogen more reliably than DREIDING force field. The simulations showed the density values of adsorbed hydrogen in the small pores of the interpenetrating IRMOFs are higher than those in the larger pores of the non-interpenetrating IRMOFs, and the diffusion of the hydrogen molecules in the interpenetrating IRMOFs is highly restricted compared to the non-interpenetrating IRMOFs. From the simulation results, we concluded that the small pores created by the catenation might contribute the increase of the adsorption capacity of the interpenetrating IRMOFs.