Flexible Amorphous Metal-Organic Framework Membranes With Local Order for Gas Separations

Metal-organic framework (MOF) membranes show immense promise for energy-efficient gas separations, yet their intrinsic brittleness has precluded their processing into practical membrane modules. Here, we report a symmetry-mismatch strategy that transforms brittle crystalline MOFs into amorphous membranes possessing an extraordinary combination of polymer-like flexibility and crystal-like ultra-microporosity. This is enabled by electrified co-assembly of two structurally related MOFs with identical metal nodes and connectivity yet distinct linkers and space groups. We demonstrate the incompatible crystal symmetries disrupt long-range periodicity while using preformed subunits for the assembly could preserve local structural order. The resulting membranes demonstrate remarkable mechanical properties, with a flexural modulus of 234 MPa and a curvature of 1000 m^-1, alongside impressive gas separation performance. This work establishes a design principle for engineering mechanically resilient, high-performance amorphous materials, overcoming a critical barrier to the real-world application of advanced MOF membrane.