Fabrication of high-quality ZIF-67 tubular membranes by the self-conversion of a Co–EG layer for methanol/tert-butyl ether separation†

Abstract

Zeolitic imidazolate framework-67 (ZIF-67) membranes, with rigid micropores and excellent stability, show great potential in the pervaporation separation of methanol/tert-butyl ether (MeOH/MTBE) mixtures. However, it remains challenging to fabricate high-quality ZIF-67 membranes due to the high nucleation rate of ZIF-67 in the bulk solutions. Herein, we report the fabrication of a high-quality ZIF-67 tubular membrane by the self-conversion of a cobalt–ethylene glycol complex (Co–EG) layer that was introduced on the substrate by a dip-coating method. The highly reactive Co–EG template layer would induce the crystallization and growth ZIF-67 grains on the substrate surface, resulting in the formation of a dense ZIF-67 membrane at room temperature. The obtained MOF membrane displays an excellent separation performance in separating 14.3 wt% MeOH/MTBE mixture, presenting a total flux of 2.92 kg m⁻² h⁻¹ and separation factor of 8945. Besides, an outstanding long-term operating stability is also achieved, benefiting from the Co–EG layer acting as an anchoring medium.