Defective carbon nitride ultrathin nanosheets enriched with amidoxime groups for enhanced visible light-driven reduction of hexavalent uranium

Amidoxime-based materials have made a great contribution to the selective adsorption process in the extraction of uranium from seawater. However, traditional adsorbents with amidoxime groups are limited by adsorption capacity and adsorption rate, which greatly hinder the development of uranium extraction from seawater. Based on this, we combined the amidoxime group with carbon nitride to synthesize the amidoxime group carbon nitride (NCN-AO), which is rich in nitrogen defects. Compared with ordinary carbon nitride (CN), NCN-AO has better selectivity and uranium reduction ability. In the process of extracting uranium from seawater, soluble hexavalent uranium (U(VI)) can be reduced to insoluble tetravalent uranium (U(IV)), to achieve high-efficiency extraction of uranium. The removal rate of uranium by NCN-AO in 100 mg/L uranium solution is 99 %, and NCN-AO has specific and selective adsorption of uranium. The band structure, density of states (DOS), highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO) of NCN-AO were calculated by Density Functional Theory (DFT) method, and adsorption reduction occurred on the surface and interface of NCN-AO. The above results show that NCN-AO may be a promising material for extracting uranium from seawater.