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, A LaNb 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.