Boosting selective Cs + uptake through the modulation of stacking modes in layered niobate-based perovskites.

Selective separation of ¹³⁷ Cs is significant for the sustainable development of nuclear energy and environmental protection, due to its strong radioactivity and long half-life. However, selective capture of ¹³⁷ Cs ⁺ from radioactive liquid waste is challenging due to strong coulomb interactions between the adsorbents and high-valency metal ions. Herein, we propose a strategy to resolve this issue and achieve specific Cs ⁺ ion recognition and separation by modulating the stacking modes of layered perovskites. We demonstrate that among niobate-based perovskites, ALaNb ₂ O ₇ (A = Cs, H, K, and Li), HLaNb ₂ O ₇ shows an outstanding selectivity for Cs ⁺ even in the presence of a large amount of competing M ⁿ⁺ ions (M ⁿ⁺  = K ⁺ , Ca ²⁺ , Mg ²⁺ , Sr ²⁺ , Eu ³⁺ , and Zr ⁴⁺ ) owing to its suitable void fraction and space shape, brought by the stacking mode of layers. The Cs ⁺ capture mechanism is directly elucidated at molecular level by single-crystal structural analyses and density functional theory calculations. This work not only provides key insights in the design and property optimization of perovskite-type materials for radiocesium separation, but also paves the way for the development of efficient inorganic materials for radionuclides remediation.
(© 2024. The Author(s).)