Guest Polarizability Directed Molecular “Freezing” Within Non‐metal Porous Salt Frameworks

Abstract Isoreticular non‐metal salt frameworks with permanent porosity have emerged recently as a fantastic platform for molecular separation, but the underlying guest‐framework interactions within their charge‐separated ionic channels remain to be explored. Here, we report the first case of guest polarizability‐directed molecular “freezing” of noble gas occurring within a non‐metal porous organic ammonium framework, which bears well‐organized, high‐density chloride anions as nodes. Notably, the framework exhibits a distinctive, thermally‐independent commensurate adsorption toward highly polarizable Xe, while traditional thermodynamic adsorption behaviors are observed for Kr with lower polarizability. A remarkable Xe adsorption capacity of 1.47 mmol g −1 and a record‐high separation factor of 10.2 are thus achieved in dynamic Xe/Kr separation under ambient conditions. The practical potential for realistic Xe/Kr separation from the off‐gas of used nuclear fuel (UNF) reprocessing is demonstrated. Theoretical calculations identify the presence of multiple strong Xe⋯Cl interactions as the driving force within the size‐matching ionic channels of the salt framework.