Efficient removal of uranium under strong acid based on charge separation and protonation coupled covalent organic frameworks

Efficient removal of UO22+ from radioactive wastewater under strong acid conditions remains a significant challenge due to the competition of excess H+ for adsorption and reduction sites. Here, covalent organic framework with complete charge separation and protonation properties (DANT-BTT) was synthesized for effi-cient removal of UO22+ under strong acids. The DANT-BTT with strong electron-deficient naphthalimide signif-icantly extended light absorption and enhanced intramolecular charge transfer, which significantly improve the separation efficiency of electrons and holes. Additionally, the auxiliary coordination of hydroxyl groups after protonation provides unparalleled selectivity for UO22+ in strong acids, effectively preventing the competition of H+ for adsorption sites. Protonation of nitrogen atoms and ketones also extends light absorption and store electrons, further enhancing the photocatalytic performance of DANT-BTT. Consequently, DANT-BTT can ach-ieve 71 % photoreduction UO22+ efficiency (pH 1) after 60 min irradiation, where dark adsorption accounts for 43 %. This work provides a strategy for the efficient reduction of U(VI) under strong acids.