Improved CO2/CH4 separation performance of mixed‐matrix membrane by adding ZIF‐7‐NH2 nanocrystals

Abstract Membrane‐based technology is an attractive alternative in terms of CO 2 separation. Pebax‐based membranes are regarded as potential candidates for CO 2 separation due to the favorable interaction between its poly (ethylene oxide) chains with CO 2 molecules and inorganic fillers. However, the separation performance for CO 2 /CH 4 mixture is still suffered from the moderate gas permeability and selectivity. To overcome this problem, in this work, amino‐functionalized zeolite imidazolate framework (ZIF‐7‐NH 2 ) nanocrystals were used as fillers to blend with Pebax 1657 for fabricating mixed‐matrix membranes (MMMs). XRD, Brunauer–Emmett–Teller (BET), scanning electron microscope, and 1 H nuclear magnetic resonance characterization indicated that ZIF‐7‐NH 2 with the highest crystallinity was synthesized. Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and Young's modulus showed that it has good interfacial interaction. Gas separation test results showed that both the CO 2 permeability and CO 2 /CH 4 selectivity of the 31 wt% ZIF‐7‐NH 2 /Pebax MMMs increased by 80 and 170%, respectively. The improved performance is attributed to the addition of ZIF‐7‐NH 2 nanocrystals and the favorable interfacial interactions between the polymer and ZIF‐7‐NH 2 nanocrystals. Furthermore, the polyvinylidene fluoride supported hollow fiber composite membranes also exhibit the long‐term stability for CO 2 /CH 4 separation.