High-Flux ZIF-8 Membranes on ZnO-Coated Supports for Propane/Propylene Separation

Zeolitic-imidazolate framework ZIF-8, a subclass of metal-organicframeworks (MOFs) with sodalite topology, has been a promising candidatefor gas separation applications. Nevertheless, fabricating a high-fluxpropylene-selective ZIF-8 membrane is still challenging owing to theintrinsic crystalline nature of ZIF-8. In this study, an effectivevapor-phase technique has been used to synthesize thin ZIF-8 membranes.ZnO was coated on anodic alumina oxide (AAO) supports via atomic layerdeposition (ALD). The ZnO layer was vapor-phase treated with 2-methylimidazole, which converted the ZnO layer to ZIF-8. The vapor-phasesynthesized ZIF-8 membranes were evaluated for propylene/propane separation.With a ZIF-8 layer of similar to 400 nm thickness, a high propylene/propaneseparation factor of 58 was obtained, concomitant with a high propylenepermeance of 3.6 x 10(-7) mol m(-2) s(-1) Pa-1. It was found thatthe vapor-phase solvent-free synthesis minimized the number of chemicalsneeded to fabricate a thin, highly permeable, and propylene-selectiveZIF-8 membrane.

Automated summary

A thin ZIF-8 membrane was successfully synthesized using an effective vapor-phase technique, which involved converting a ZnO layer to ZIF-8. This membrane exhibited high selectivity and permeability for propylene/propane separation.