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

ABSTRACT 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.