Metal–Organic Framework Crystal–Glass Composite Membranes with Preferential Permeation of Ethane

Abstract Metal–organic framework (MOF) glass is an easy to process and self‐supported amorphous material that is suitable for fabricating gas separation membranes. However, MOF glasses, such as ZIF‐62 and ZIF‐4 have low porosity, which makes it difficult to obtain membranes with high permeance. Here, a self‐supported MOF crystal–glass composite (CGC) membrane was prepared by melt quenching a mixture of ZIF‐62 as the membrane matrix and ZIF‐8 as the filler. The conversion of ZIF‐62 from crystal to glass and the simultaneous partial melting of ZIF‐8 facilitated by the melt state of ZIF‐62 make the CGC membrane monolithic, eliminating non‐selective grain boundaries and improving selectivity. The thickness of CGC membrane can be adjusted to fabricate a membrane without the need of a support substrate. CGC membranes exhibit a C 2 H 6 permeance of 41 569 gas permeation units (GPU) and a C 2 H 6 /C 2 H 4 selectivity of 7.16. The CGC membrane has abundant pores from the glassy state of ZIF‐62 and the crystalline ZIF‐8, which enables high gas permeance. ZIF‐8 has preferential adsorption for C 2 H 6 and promotes C 2 H 6 transport in the membrane, and thus the GCG membrane exhibits ultrahigh C 2 H 6 permeance and good C 2 H 6 /C 2 H 4 selectivity.