Tailoring the electronic microenvironment of polymeric carbon nitride to accelerate reduction crystallization kinetics of uranium extraction from seawater

Photo-assisted uranium extraction from seawater is regarded as a potential technique for uranium resource recovery. Here, we report a polymeric carbon nitride (SCN-C 3 N 4 ) synthesized via a one-step calcination method, which combines cyano groups (-C≡N) modification and S atoms doping for efficient uranium extraction. By DFT calculations, we confirm that the integration of -C≡N modification and S atoms doping effectively reconstructed the charge distribution on the inside of the heptazine rings, forming a strong driving force for the migration of photogenerated electrons to the reactive sites. Accordingly, the reaction rate constant of SCN-C 3 N 4 ( k  = 0.00843 min −1 ) is 20.07 times higher than that of g-C 3 N 4 ( k  = 0.00042 min −1 ). Finally, the SCN-C 3 N 4 exhibits a remarkable uranium extraction capacity of 6.05 mg g −1 in natural seawater. Relying on various spectroscopic techniques, we identify the reaction process of uranium, which is captured by -C≡N, forming UO 2.34 crystallization under the joint action of electrons and free radicals. Furthermore, SCN-C 3 N 4 demonstrates excellent antibacterial and corrosion resistance, breaking the bottleneck of uranium extraction from marine biofouling. This work provides an example of designing novel polymeric carbon nitride materials for uranium extraction.