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

Selective separation of 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 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, ALaNbO (A = Cs, H, K, and Li), HLaNbO shows an outstanding selectivity for Cs even in the presence of a large amount of competing M ions (M = K, Ca, Mg, Sr, Eu, and Zr) 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.