Boosting pervaporation performance of ZIF-L/PDMS mixed matrix membranes by surface plasma etching for ethanol/water separation

Mixed matrix membranes (MMMs) have been shown great performance and remarkable stability for diverse molecular separations. Considering that the density of MOFs is usually higher than that of polymer doping solution, the upper separation layer surface of MMMs is enriched by the polymer matrix, compromising the membrane performance. In this study, the asymmetric separation layer of MOF-filled MMMs was etched by the long-distance and dynamic low-temperature (LDDLT) plasma for enhanced ethanol permselective pervaporation. The thickness of separation layer decreased and the MOF amount on surface increased after the LDDLT plasma etching, which dramatically reduced the molecular permeation resistance and improved the membrane performance. Under optimal plasma conditions, the etched MMMs exhibited the superior permeation flux of 1120 g·m⁻²·h⁻¹ (60% more than that of unetched membrane) and the separation factor of 12.3 (1.16 times as much as that of unetched membrane) in separation of 5 wt% ethanol aqueous solution at 40 °C.