Magnetic‐Field‐Driven Fabrication of Robust Metal‐Organic Framework Membranes for Efficient Propylene/Propane Separation

Abstract Zeolitic imidazolate framework‐67 (ZIF‐67) membranes hold great promise in efficiently separating propene/propane mixtures. However, achieving highly permselective ZIF‐67 membranes remains challenging due to unruly crystal nucleation and poor grain boundary structure. Herein, a magnetic‐field‐driven approach is reported to fabricating high‐quality ZIF‐67 membranes on anodized aluminum oxide substrates at room temperature. The presence of a magnetic field increases the nucleation rates by shortening the induction period, facilitates the orderly and rapid migration of Co 2+ ions, optimizes the nucleation of ZIF‐67 crystallites on the substrate, and inhibits the excessive crystal growth of ZIF‐67 grains. These factors collectively contribute to improving the grain boundary structure and suppressing inter‐grain defects in MOF membranes. The resulting ZIF‐67 membranes, with a thickness of less than 480 nm, exhibit a superior propylene/propane separation performance, featuring a separation factor of 135 and a propylene permeance of 2.3 × 10 −8  mol m −2 s −1  Pa −1 . The magnetic‐field‐driven approach is expected to greatly promote the development of MOF membranes for highly efficient and energy‐saving separations.