Methane diffusion mechanism in catenated metal–organic frameworks

In this work, molecular dynamics simulations were performed to investigate the gas diffusion mechanism in catenated metal–organic frameworks (MOFs), for which methane was adopted as a probe and two catenated IRMOFs with interwoven structure, IRMOF-11 and IRMOF-13, were considered. This work reveals that the diffusion pathways of methane molecules in catenated MOFs are mainly governed by the strong confinement in catenation regions, leading to a 3D diffusion along the sheets formed by the A-regions (xy-direction) as well as from one A-region to another by crossing a B-region (z-direction). In addition, the present work shows that the effect of catenation on methane diffusivity is very large, much larger than that on hydrogen diffusivity at room temperature, and that both adsorption selectivity and dynamic selectivity of gas mixtures may be enhanced largely in catenated MOFs, indicating that catenation is a good strategy to improve the overall performance of a material as a membrane in separation applications.