Supercritical Processing of a Highly C3H6-Permselective ZIF-8 Membrane on a Tubular Porous α-Al2O3 Substrate

Highly permselective metal–organic framework (MOF) membranes would play a significant role in energy-efficient separation if they could be prepared in a sustainable manner, but it remains challenging, in particular, on tubular ceramic supports. In this work, we proposed a supercritical fluid (SCF) process to sustainably prepare tubular ZIF-8 membranes with high performance. Both the high quality of the ZnO layer and high diffusivity of supercritical CO2 resulted in fewer grain boundary defects and superior microstructure, thus leading to enhanced C3H6/C3H8 selectivity. The ideal C3H6/C3H8 selectivity of the tubular ZIF-8 membrane was 120.6, which was better than that of most tubular ZIF-8 membranes. Furthermore, after SCF processing, residual 2-methylimidazole and released CO2 could achieve efficient and sustainable reuse, leading to zero pollutant emissions. Most importantly, this represents the first study of SCF-assisted processing of MOF membranes on tubular supports, thereby showing great promise in their scalable production.