Facile synthesis of Co-gallate membranes under magnetic field for effective ethylene/ethane separation

Metal-organic framework (MOF) membranes, particularly cobalt-based gallate (Co-gallate) membranes, possess great potential for the efficient separation of ethylene/ethane (C 2 H 4 /C 2 H 6 ) mixtures due to their excellent sieving properties. However, the poor nucleation of MOF crystals on the substrate poses a challenge in the fabrication of high-quality Co-gallate membranes. In this work, we propose a facile and environmentally friendly approach to prepare continuous Co-gallate membranes at room temperature via magnetic field assistance. The external magnetic field, perpendicular to the substrate surface, promotes directional ion movement, improves the coordination ability of metal centers, and promotes deprotonation of ligands. These collectively facilitate the crystallization and growth of MOF crystals on the substrate by advancing MOF nucleation and enhancing nucleation density. The controllable growth of MOF membranes can also be achieved under the influence of magnetic field. The obtained Co-gallate membrane has a thickness of merely 400 nm, and exhibits superior performance in C 2 H 4 /C 2 H 6 separation. This work highlights the considerable potential of magnetic fields in the fabrication of various MOF membranes for diverse applications.