Identifying highly selective MOFs for CH4/H2 separations using computational tools

Abstract

The large number of metal organic frameworks (MOFs) represents both an opportunity and a challenge for identification of materials exhibiting promising properties in gas separations. We used molecular simulations to screen 250 different MOP structures in order to examine their adsorption-based CH4/H-2 separation performances. Adsorption selectivity, working capacity, sorbent selection parameter, and regenerability of MOFs were calculated and compared with those of traditional nanoporous materials. The accuracy of simple models that can predict adsorption selectivity of MOFs based on structural properties of materials was discussed. With the use of molecular dynamics, gas diffusivities were computed in the MOFs which were identified as the top performing materials for adsorption-based CH4/H-2 separation. Membrane selectivities of these MOFs were predicted to discuss kinetic separation performances of materials. Results showed that there is a significant number of MOFs that exhibit extraordinarily large adsorption-based and membrane-based CH4/H-2 selectivities compared to well-known nanoporous materials such as zeolites. Using MOFs as adsorbents rather than membranes would be more efficient in CH4/H-2 separation.