Polyzwitterion-grafted UiO-66-PEI incorporating polyimide membrane for high efficiency CO2/CH4 separation

Abstract Mixed matrix membrane (MMM) has been a promising selection to surpass the Robeson limitation of commercial polymer membranes. Here, we present high selectivity MMMs based on structural regulation of UiO-66-PEI fillers grafted with polyzwitterion. XRD, FTIR, SEM and TGA characterization techniques were used to evaluate the structure and properties of UiO-66-PEI@pSBMA and MMMs. It can be found that the introduction of branched polyethyleneimine (PEI) and poly(sulfobetaine methacrylate) (pSBMA) can not only avoid the agglomeration of UiO-66-NH2 and improve the compatibility between the polymer matrix and filler particles. In addition, the UiO-66-PEI@PSBMA can bond with a noticeable amount of amino groups and water molecules to promote the transportation of CO2 in the membrane. Impressively, the incorporation of 15 wt% UiO-66-PEI@pSBMA into the PI membrane increases the gas perm-selectivity of the MMM and exceed the Robeson upper bound. Therefore, PEI post-modification and polyzwitterion grafting of UiO-66-NH2 provides a good prospect for eliminating interface defects and enhancing the gas separation performance of MMMs