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

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.