Defect engineering-induced charge redistribution in Zn-PBA frameworks for high-efficiency and durable cesium ion capture

The precise regulation of anion vacancies in Prussian blue analogs (PBAs) remains a critical challenge for addressing the trade-off between cesium ion adsorption performance and structural robustness. Herein, we develop a thermal annealing strategy to controllably introduce cyanide vacancies (VCN) into Zn-PBA frameworks, achieving an optimal balance between enhanced cesium adsorption capacity, kinetics and stability. Zn-PBAT250 with an optimal VCN density (21%) exhibits an exceptional Cs+ adsorption capacity of 537.84 mg g−1, reaching equilibrium within 30 min-twice as fast as pristine Zn-PBA. Moreover, the highly selective adsorption in complex environments is evidenced by distribution coefficients (Kd) exceeding 104 mL g−1 even under excessive competing ions (Na+, K+, Mg2+, Ca2+). Remarkably, Zn-PBAT250 demonstrates outstanding recyclability (>92% capacity retention over 10 cycles) and practical applicability in column/membrane filtration systems, treating >1000-bed volumes of Cs+-contaminated water with >99% efficiency. Molecular dynamics simulation and density functional theory calculations reveal that the engineered vacancies significantly reduce the Cs+ incorporation energy barrier (Eads = −5.15 and −4.63 eV for Zn-PBA with/without VCN, respectively), and VCN sites create localized electron-deficient regions, promoting strong Cs+-framework interactions via optimized charge redistribution. This work provides a universal defect-engineering paradigm for designing high-performance adsorbents toward environmental remediation and energy storage.