W-N-C Tandem Catalytic Centers Mediating Efficient Charge Transfer for the Enhanced Radical-Path U(VI) Photoreduction

Photocatalytic reduction of uranium is pivotal for environmental remediation and sustainable resource utilization. Nevertheless, the precise control over the reaction pathway and the concurrent optimization on charge separation efficiency remain formidable challenges. Herein, W─N─C coordination was fabricated through the incorporation of WO_3-x with three-dimensional ordered macropores g-C₃N₄ (3DOM g-C₃N₄). The tandem catalytic center simultaneously enhanced the intrinsic activity of g-C₃N₄ and enabled an efficient radical reduction pathway of U(VI). The formation of W─N─C coordination and structural distortion of the tri-s-triazine units enhanced n → π^* and π → π^* transition, resulting in a narrowed bandgap and improved visible-light harvesting. Moreover, the Lewis-acidic W⁶⁺ sites promoted O₂ adsorption, facilitating the selective generation of $O_2^{-}$ . The radical-mediated U(VI) reduction pathway was thermodynamically favored, where W sites acted as electron-accepting centers, with the W─N─C coordination serving as a charge-transfer channel under a built-in electric field, enabling the Z-scheme migration. Consequently, the optimized catalyst (CW-2) exhibited a U(VI) removal rate of 98.6% (capacity of 557.56 mg/g) within 16 min, the removal efficiency was reduced to a minute scale, and the impractical oxygen exclusion was no longer a significant concern. This work established a paradigm for creating "all-in-one" photocatalytic active centers through targeted atomic-scale interface design.