<p>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 (V_CN) into Zn-PBA frameworks, achieving an optimal balance between enhanced cesium adsorption capacity, kinetics and stability. Zn-PBAT₂₅₀ with an optimal V_CN 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 (<i>K</i>_d) exceeding 10⁴ mL g⁻¹ even under excessive competing ions (Na⁺, K⁺, Mg²⁺, Ca²⁺). Remarkably, Zn-PBAT₂₅₀ demonstrates outstanding recyclability (&gt;92% capacity retention over 10 cycles) and practical applicability in column/membrane filtration systems, treating &gt;1000-bed volumes of Cs⁺-contaminated water with &gt;99% efficiency. Molecular dynamics simulation and density functional theory calculations reveal that the engineered vacancies significantly reduce the Cs⁺ incorporation energy barrier (<i>E</i>_ads = −5.15 and −4.63 eV for Zn-PBA with/without V_CN, respectively), and V_CN 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.</p>