Manipulating Lewis acid-base pairs on carbon nitride with synergistic catalytic sites for photocatalytic aerobic uranyl reduction

Photochemical reduction of hexavalent uranium (U(VI)) to insoluble tetravalent uranium (U(IV)) presents a sustainable catalytic conversion approach for the alleviation of growing nuclear environmental pollution. However, achieving superior U(VI) reduction activity is hindered by the challenges of low carrier separation efficiency, limited active sites, and unclear catalytic mechanisms. Here, we report a K/PD/CN featuring multiple catalytic sites for photocatalytic U(VI) reduction. The Lewis base sites, provided by the terminal C ≡ N groups, facilitate the reduction of hexavalent U(VI). The electron-deficient K atom acts as the Lewis acid site to oxidize CH 3 OH to CH 2 O. The coexistence of acid and base sites results in a strong synergistic effect during the photocatalytic aerobic reduction of U(VI). P doping sites cause charge redistribution and boost Lewis acid-base active sites. Spectroscopy and density functional theory calculations show that efficient charge separation is achieved through electron delocalization within the K/PD/CN The combination of abundant active sites and effective carrier separation leads to an impressive 99.2 % U(VI) remove efficiency in 30 min for K/PD/CN, which is approximately 5.6 times faster than CN. This study presents a novel approach for advancing the high-efficiency reduction of uranyl with well-designed multisite Lewis acid-base catalysts. • K/PD/CN with well-defined Lewis acid and base sites were constructed. • Density functional theory calculations evidence the presence of multiple carriers delocalized center. • The terminal C ≡ N groups on K/PD/CN act as Lewis base sites and the K atoms act as Lewis acid sites. • The K/PD/CN shown superior U(VI) efficiency rate over 99.2 % in 30 min under atmospheric air conditions.