Synergistic improvement in gas separation performance of MMMs by porogenic action and strong molecular forces of ZIF-93

Abstract

In the present study, ZIF-93 metal–organic frameworks were prepared. N2 adsorption tests revealed that the particle size, specific surface area, and pore size of ZIF-93 were 30 nm–45 nm, 869.40 m2/g, and 0.36 nm, respectively. Pebax-based mixed matrix membranes (MMMs) were prepared using ZIF-93 as the filler. The pore diameters of ZIF-93 lied between the kinetic diameters of CO2 and N2; thus, its pore structure provided a fast transfer channel for CO2 and increased the permeability of the membrane. Further, X-ray diffraction showed that the membrane became denser upon introducing ZIF-93 because of the formation of a bridging structure between the Pebax molecular chains and ZIF-93. A denser stacking by moving the Pebax molecular chains closer to each other effectively bettered the CO2 selectivity of the mixed matrix membrane. The test results showed that when the ZIF-93 loading was 10 wt%, the CO2 permeability was 84.85 barrer and the CO2/N2 selectivity was 65.76 at 0.4 MPa, which are 51.57 % and 65.50 % higher than those of the pure Pebax membrane, respectively. When the feed pressure was increased to 0.8 MPa, the CO2 permeability was 94.5 barrer and the CO2/N2 selectivity is 87.5, which are 51.57 % and 65.50 % higher compared with those of the pure Pebax membrane, in order. The membrane performance significantly exceeded that of the 2008 Robeson curve.