Fabricating Open-Framework Using Polyoxovanadate Clusters for Efficient Removal of Radioactive Cs+ and Sr2+

Innovation of 137 Cs + and 90 Sr 2+ ion exchangers is achieved through heteroatom-bridged integration of polyoxovanadate clusters, whose soft Lewis basic nature and large size promote the selective capture of cesium/strontium radionuclides. The radiolytically stable Na 6 P 4 V 10 O 34 ·19H 2 O ( VPO-1 ) features an interlinkage of {NaV 10 O 26 } clusters and phosphorus bridges, forming nanoscale voids with hydration-lubricated sodium ions. This structure endows VPO-1 with remarkable exchange kinetics ( k 2 Cs = 3.774 g mg −1 min −1 ; k 2 Sr = 1.376 g mg −1 min −1 ), equilibrium removal ( R > 99.3% within 5–10 min), and maximum capacities ( q m Cs = 300.32 mg g −1 ; q m Sr = 113.00 mg g −1 ). The exchange mechanism is illuminated through single-crystal XRD by revealing cluster-vacancy pathways and ionic-radius-dependent adsorption sites. VPO-1 exhibits stability across pH = 3–12, with exceptional K d Cs and K d Sr values above 10 5 mL g −1 , and high selectivity for Cs + and Sr 2+ over various competing ions. These properties enable excellent column filtration performance ( R = 99%–100%) for mixed Cs + and Sr 2+ during a 3000 mL test. Deep cleaning of these ions is also possible via suction filtration using an ultra-thin VPO-1 /PTFE membrane, with high exchange activity ( R = 98.8%–99.9%) retained after simple regeneration with 2 m NaCl, offering significant potential for nuclear wastewater treatment applications.