ZIF-8 membranes with improved reproducibility fabricated from sputter-coated ZnO/alumina supports

• Partial self-conversion of sputtering ZnO layer to continuous ZIF-8 membrane.
• The reproducibility is improved, compared to that from sol–gel coated ZnO layer.
• There exists an optimal amount of ZnO precursor for high quality ZIF-8 membranes.
• Lower pressure drop favors better performance for propylene/propane separation.

Zeolitic imidazolate framework-8 (ZIF-8) membrane has shown great potential for propylene/propane separation based on molecular sieving mechanism. Although diverse synthesis strategies were applied to prepare ZIF-8 membranes, it is still a challenge for reproducible fabrication of high-quality membranes. In this study, high-quality ZIF-8 membranes were prepared through hydrothermal synthesis under the partial self-conversion of sputter-coated ZnO layer on porous α-alumina supports. The reproducibility was significantly improved, compared with that from sol–gel coated ZnO layer, due to the highly controllable sputtering deposition of ZnO precursor. The relationship between the quality of as-synthesized membrane and amount of deposited ZnO was also determined. The effect of pressure drop in C3H6/C3H8 separation on separating performance was also examined.