Linker Chlorination Enhances Xe Adsorption and Xe/Kr Separation in Metal-Organic Frameworks

Efficient separation of Xe/Kr mixture remains a challenge, due to their chemical inertness and the striking similarity of their physicochemical properties. In this work, the chlorine-decorated metal-organic framework (MOF) of JXNU-24(Cl) and its pristine JXNU-24 are presented for Xe/Kr separation. The chlorine-functionalized framework with a more polar pore microenvironment exhibits a stronger binding affinity toward Xe. Consequently, JXNU-24(Cl) exhibits a Xe/Kr adsorption selectivity of 10.3 and outstanding separation performance with a high productivity of 184 L kg-1 for high-purity Kr (>99.9%). Computational simulations reveal that the presence of chlorine substituents generates polar pore surfaces, which preferentially interact with the more polarizable Xe molecules, thereby enhancing Xe-framework interactions and Xe/Kr selectivity for JXNU-24(Cl). This work achieves preferential Xe recognition via framework polarity modulation and offers an effective molecular design strategy for constructing MOFs for efficient Xe/Kr separation.