An argon‐selective, flexible Al‐ MOF enabled by conformational adaptation for high‐purity oxygen production via vacuum‐pressure swing adsorption

The removal of trace argon from oxygen is among the most challenging separations due to their nearly identical physicochemical properties. Moving beyond conventional strategies reliant on strong, static binding sites, this work introduces a flexible aluminum‐based MOF, Al‐CHDC, constructed with a conformationally adaptable trans‐1,4‐cyclohexanedicarboxylate linker. Molecular simulations reveal that adsorption of the dumbbell‐shaped O 2 molecule induces significantly greater torsional distortion in the linker compared to spherical Ar, imposing a higher conformational energy barrier for O 2 . This creates a “conformational gating” effect, whereby the framework functions as an energy filter, thermodynamically favoring Ar adsorption. Consequently, Al‐CHDC exhibits an IAST selectivity of 1.36 at 298 K, with Ar uptake of 7.56 cm 3 /g. Al‐CHDC was further shaped into mechanically robust pellets, and its performance was validated under practical vacuum‐pressure swing adsorption (VPSA) conditions. This work provided a new pathway to address high‐difficulty molecular separations through the selective modulation of adsorption energy landscapes.