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

Abstract Innovation of ¹³⁷Cs⁺ and ⁹⁰Sr²⁺ 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 Na₆P₄V₁₀O₃₄·19H₂O (VPO‐1) features an interlinkage of {NaV₁₀O₂₆} clusters and phosphorus bridges, forming nanoscale voids with hydration‐lubricated sodium ions. This structure endows VPO‐1 with remarkable exchange kinetics (k₂^Cs = 3.774 g mg⁻¹ min⁻¹; k₂^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 10⁵ mL g⁻¹, and high selectivity for Cs⁺ and Sr²⁺ over various competing ions. These properties enable excellent column filtration performance (R = 99%–100%) for mixed Cs⁺ and Sr²⁺ 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.