Linker Engineering in Flexible Metal–Organic Frameworks Suppressing Slipping‐Off Effect for Efficient Xe/Kr Separation

ABSTRACT Flexible metal–organic frameworks (MOFs) with guest‐selective gate‐opening behavior are attractive for gas separations because they combine high selectivity with high capacity, yet their dynamic separation performance is often compromised by slipping‐off effects. Here, we report a series of tetrazole‐pillared MOFs, Zn(pzdc)(L) (pzdc = 3,5‐pyrazoledicarboxylate; L = tetrazole derivatives), for efficient Xe/Kr separations, in which linker engineering with polar methyl or amino substituents reprograms framework dynamics and confined microenvironments to suppress slipping‐off and promote Xe capture at low pressures through an adaptive molecular‐recognition mechanism. Breakthrough experiments reveal a clear evolution in separation behavior, from severe Xe slipping‐off in Zn(pzdc)(tz), to partial suppression in Zn(pzdc)(mtz), and ultimately to enhanced Xe/Kr separation in Zn(pzdc)(atz). Consequently, Zn(pzdc)(atz) affords > 99.99% pure Kr with a productivity of 107.5 L L −1 and a dynamic Xe uptake of 71.3 L L −1 from a Xe/Kr (20/80) mixture, while enabling trace Xe capture from simulated used nuclear fuel off‐gas. In situ single‐crystal X‐ray diffraction reveals that linker engineering reinforces the host–guest interactions governing gate opening and amplifies the guest‐induced structural response, enabling framework opening at extremely low Xe partial pressures and sustained dynamic Xe capture.