Atomistic Simulations for Adsorption, Diffusion, and Separation of Gas Mixtures in Zeolite Imidazolate Frameworks

Atomically detailed simulations were used to assess the performance of zeolite imidazolate frameworks (ZIFs) for separation of CH4/H2, CO2/CH4, and CO2/H2 mixtures to provide information for material selection in adsorbent and membrane designs. Adsorption isotherms and self-diffusivities of gas mixtures in ZIFs were computed using grand canonical Monte Carlo and equilibrium molecular dynamics simulations, respectively. Adsorption selectivity, diffusion selectivity, and permeation selectivity of ZIF membranes were calculated on the basis of the results of atomistic simulations. Selectivity and permeability of gases through ZIF membranes were compared to well-known zeolite membranes and metal organic framework (MOF) membranes. Results showed that ZIF-3 and ZIF-10 exhibit significantly higher adsorption and permeation selectivities for separation of all gas mixtures as compared to widely studied MOF membranes.