Ultra-highly efficient enrichment of uranium from seawater via studtite nanodots growth-elution cycle.

Consecutive uranium extraction from seawater is a promising approach to secure the long-term supply of uranium and the sustainability of nuclear energy. Here, we report an ultra-highly efficient strategy via studtite nanodots growth with impressive uranyl uptake capacity of ~ 154.50 mg/g from natural seawater in 12 consecutive days (i.e., average for ~ 12.875 mg/g/day). Uranyl can be extracted as studtite under visible light via the reaction between the adsorbed uranyl and the photogenerated HO with imine-based Covalent-Organic Framework photocatalysts. In detail, over Tp-Bpy, Tp-Bpy-2 and Tp-Py with multiple uranyl chelating sites, uranyl is found extracted as studtite nanodots which can be eluted readily, while over Tp-Bd and Tb-Bpy, uranyl is transformed into studtite nanorods that is more inert for elution. Abundant chelating sites of uranyl via structural regulation of COF photocatalysts are proved to facilitate the formation and efficient elution of studtite nanodots.