A negatively-charged supramolecular trap for precisely catching strontium ion

Due to the analogous physicochemical properties and weak coordination ability of alkali and alkaline earth metals, accurate separation of radioactive 90Sr from groundwater or seawater still presents a big challenge in environmental radioactivity remediation. Here we mimic the complexation behavior of molecular crown-ether carboxylic acids to construct an elegant negatively charged supramolecular trap in an anionic crown ether-based metal-organic framework (ZJU-X99) for precisely catching Sr2+. Owing to the synergistic effects of electrostatic interactions arising from the In(COO)4- nodes and supramolecular host-guest recognition from the 18-crown-6 rings, ZJU-X99 exhibits rapid adsorption kinetics (1 min), high adsorption capacity (263 mg/g), and exceptional selectivity for Sr2+ even when 1000-fold of Na⁺, K⁺ and Cs⁺ coexist. Relative to alkali metals, Sr2+ ions are intricately ensconced within the supramolecular trap, resulting in lowest binding energy and minimal structural alterations. Dynamic column experiments and radioactive 90Sr decontamination trials further validate its practical application prospects. Our findings offer valuable insights into the design of supramolecular frameworks featuring tailored binding sites for targeted ions.