In Situ Incorporation of Macromolecules in Zr-MOF Membranes for Separation of Organic Azeotropic Mixtures

Metal–organic framework (MOF) membranes with adjustable angstrom-scale channels and versatile topological structures are promising for molecular separation. However, it remains a challenge to construct MOF membranes with precisely tuned pore sizes and tailored molecular affinity for achieving high-efficiency liquid molecular separation, particularly for organic azeotropic mixtures. Herein, we proposed an in situ macromolecule incorporation strategy to fabricate a Zr-MOF membrane with a tunable pore microenvironment for pervaporation separation of butanol–water and ethanol–ethyl acetate azeotropic mixtures. The membranes were prepared by an in situ interfacial growth process. The amino macromolecules (poly(ether imide), PEI) were dispersed into a metal cluster solution, followed by coordination with ligands on the substrate surface for membrane synthesis, wherein the macromolecule was in situ incorporated within MOF pore apertures. The incorporated macromolecule narrowed the membrane pore size and provided molecularly accelerated transport sites, thus facilitating the fast and selective transport of water or ethanol molecules. When incorporating PEI (MW = 10,000 g·mol–1) at a content of 1 wt %, the resulting MOF membrane displayed excellent separation performances with a total flux of 2.22 kg·m–2·h–1 and a separation factor of 140 for the ethanol–ethyl acetate system, and a total flux of 8.52 kg·m–2·h–1 and a separation factor of 1620 for the butanol–water system, outperforming the performance of state-of-the-art membranes. The proposed macromolecule-incorporated angstrom-sized channels demonstrate considerable potential for broad application in other fields, e.g., single-atom catalysis, sensing, and energy conversion.