Mixed-Linker-Directed Seed-Free Growth of CO2-Selective MOF-303 Membranes

초록

Realizing metal-organic framework (MOF) membranes for industrial gas separations hinges on scalable routes to dense, low-defect layers. We report a mixed-linker, seed-layer-free strategy for the one-step growth of aluminum MOF-303 membranes directly on porous alpha-alumina supports. Partial substitution of 3,5-pyrazoledicarboxylic acid (H3PDC) with 2,5-furandicarboxylic acid (FDCA) accelerates interfacial nucleation and promotes continuous membrane formation, obviating the conventional seeding step required for MOF-303. Structural and spectroscopic analyses confirm uniform FDCA incorporation without perturbing the intrinsic framework chemistry. The resulting mixed-linker membranes, exemplified by MOF-303(P7F3) and MOF-303(P6F4), deliver outstanding CO2 separations: for MOF-303(P6F4), CO2/N2 separation factors reach 170 and 236 at 20% and 50% CO2 feeds, respectively; CO2/CH4 separation factors reach 431 and 393 under the same conditions, surpassing the 2019 polymeric-membrane upper bound. Molecular simulations also indicate that FDCA incorporation leaves intrinsic adsorption and diffusivity largely unchanged, attributing the observed performance gains to improved membrane morphology and grain-boundary suppression arising from the mixed-linker-directed growth. This simple, versatile route enables dense, high-selectivity MOF-303 membranes without seeding and is readily extendable to MOF systems where conventional in situ synthesis fails to yield defect-minimized membranes.

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