Polymer-supported ultra-thin ZIF-67 membrane through in situ interface self-repair

Metal-organic framework (MOF) membranes have significant potential for use in efficient gas separation. However, fabricating polymer substrate-supported ultra-thin MOF membranes with no defects remains a challenge. Herein, we proposed an in situ interface self-repair strategy for fabricating ultra-thin and defect-free ZIF-67 membranes for the first time. This was realized by preparing a polyvinyl alcohol (PVA)-Co2+ interfacial layer containing a Co2+ ion layer and a PVA-Co2+ complex layer. The PVA-Co2+ interfacial layer released Co2+ ions and acted as a metal source to form ZIF-67 membranes by reducing the coordination rate of Co2+ ions with 2-methylimidazole. The embedded Co2+ ions functioned as anchor sites for the nucleation of ZIF-67 membrane assisted by the interface-enhanced deprotonation of 2-methylimidazole. Especially, the slow release of Co2+ ions from the PVA-Co2+ interfacial layer facilitated self-repair of defects to form a continuous and dense MOF layer. ZIF-67 membranes, 80-280 nm thick, were successfully synthesized and demonstrated unprecedented CO2 permeance and good CO2/N2 selectivity. This work provides a promising strategy for the fabrication of ultra-thin and defect-free MOF membranes on polymeric support layers for use in practical applications.