Atomically Detailed Models for Transport of Gas Mixtures in ZIF Membranes and ZIF/Polymer Composite Membranes

In this work, we introduced atomic models for transport of single component gases (CH4, CO2, H-2, and N-2) and binary gas mixtures (H-2/CO2, H-2/N-2, H-2/CH4) in zeolite imidazolate framework (ZIF) membranes and ZIF/polymer composite membranes. The predictions of atomic models were validated by comparing with the available experimental data for a ZIF-90 membrane. Motivated from the good agreement between experimental measurements and predictions of our molecular simulations for single gas and mixture permeances, we extended atomic modeling methods to an unfabricated ZIF membrane, ZIF-65, for predicting its separation performance. Various selectivities of ZIF membranes such as ideal selectivity, mixture selectivity, adsorption selectivity, and diffusion selectivity were computed for a wide range of operating conditions to assess the potential of ZIF membranes in H-2/CO2 separations. We then combined atomic simulations with continuum modeling to estimate the performance of ZIF-90/Matrimid and ZIF-90/Ultem composite membranes for gas separations. Our theoretical predictions agreed very well with the experimental measurements for these two composite membranes, and therefore, we assessed the performances of several ZIF/polymer membranes composed of various polymers, ZIF-90 and ZIF-65, for separation of H-2 from CO2.