Atomic insight into the transport mechanism of CO2/N2 molecules passing through UiO-66/PDMS membranes

Abstract

Mixed matrix membranes (MMM) prepared by adding MOF filler to polymeric membranes are expected to overcome the trade-off effect inherent in membranes and improved the efficiency of separation and CO2 capture. In this work, concentration-gradient-driven molecular dynamics (CGD-MD) was employed to explore gas permeability of pure CO2/N2 and their mixture in PDMS membrane, UiO-66 membrane and UiO-66/PDMS membrane, respectively. The transport mechanism of gas molecules in the membranes was illustrated from molecular level. Moreover, the simulated permeability and predict permeability were compared to investigate the effect of the porosity at the UiO-66/PDMS interface on gas transport in mixed matrix membrane. The competitive effect between CO2 and N2 molecules in mixture could explain their different permeability in different membranes. The pore sizes distribution map and pore connectivity diagrams within UiO-66/PDMS membrane shown that the relative larger pore size and interconnectivity voids are formed in the interfacial region, and the interfacial porosity formed in UiO-66/PDMS membrane shown a positive effect on pure N2 transport and almost no effect on pure CO2 permeability. While the selectivity of UiO-66/PDMS membrane for the mixed gas case is improved because CO2 increases the retention time of N2 in the membrane and decreases the N2 permeability. This work provides a worthwhile perspective on the design of high-performance membranes for separation.