The Confinement Effect of “Ion Lock” for Highly Selective Cesium(I) Capture and Recovery by a 3D Microporous Metal Oxalatophosphate

Abstract The highly selective capture of 137 Cs + from complex solutions is still challenging because of its high solubility, easy mobility, and the influence of interfering ions. Here, a reliable strategy is demonstrated for specific Cs + ion recognition and separation through constructing the confined space as an “ion lock” in the microporous framework. A new 3D microporous indium oxalatophosphate with the highly selective Cs + capture, namely [Me 2 NH 2 ] 1.5 [In 2 (PO 4 ) 0.5 (H 2 PO 4 )(HPO 4 ) 1.5 (C 2 O 4 )] (FJSM‐NINPC) is prepared. FJSM‐NINPC with excellent radiation resistance shows ultra‐fast kinetics (high removal rate of 97.63% within 1 min) and high adsorption capacity of 268.12 mg g −1 for Cs + . It can highly selectively capture Cs + under excessive competitive ions and even in environmental water samples. Furthermore, the ion exchange column filled with FJSM‐NINPC can quickly separate and recover Cs + from mixed Cs + and Sr 2+ solution (separation factor SF Cs/Sr = 249.17). Moreover, single crystal structure analysis combined with density functional theory calculations confirms that Cs + ions are “encapsulated” in channels of FJSM‐NINPC by the suitable spatial confinement and with strong Cs···O interactions. This work not only provides an unprecedented microporous metal oxalatophosphate with high Cs + selectivity but clearly reveals the Cs + capture mechanism and structure‐function relationship of microporous materials for radionuclides remediation.