In-situ constructing amidoxime groups on metal-free g-CN to enhance chemisorption, light absorption, and carrier separation for efficient photo-assisted uranium(VI) extraction.

The development of inexpensive and efficient semiconductor catalysts for photo-assisted uranium extraction from seawater remains a huge challenge. Herein, we have successfully synthesized amidoxime-rich g-CN (AO-CN) by simply amidoximing a cyano-rich precursor for photo-assisted uranium extraction from seawater. The amidoxime groups not only served as the U(VI) binding sites for efficient uranium adsorption, but also significantly improved the visible light absorption capacity and carrier separation efficiency via introducing defect energy level, resulting in the excellent photocatalytic activity for AO-CN towards photo-assisted uranium extraction. In the process of photo-assisted uranium extraction, U(VI) was first adsorbed by the amidoxime groups on the AO-CN and then reduced to U(IV), while (UO)O·2HO and (UO)O·4HO were further formed by the oxidation of U(IV) by superoxide radicals (·O). Moreover, the generated reactive oxygen species (ROS) under light endowed AO-CN with outstanding antibacterial properties, preventing the limitation of uranium extraction capacity from marine biofouling.