Visible-light-driven oxidative coupling of primary amines with high selectivity in air over Ni/Ce-doped defective carbon nitride

Visible-light-driven photocatalysis is a sustainable, low-cost, and stable, method for chemical conversion in organic processes. A novel porous g-C₃N₄ nanosheet (CN) photocatalytic material co-doped with nickel and cerium has been synthesized using a one-step thermal polymerization method. We used XPS, XRD, EPR, UV–vis DRS, SEM, and PL to disclose the structural, optical, and electrical features of the catalysts. Experiments with EPR radical trapping confirmed the existence of reactive oxygen species and holes in the photocatalytic activity. The charge transfer and separation efficiency of the produced catalysts were evaluated using EIS and photocurrent measurements. Ni/Ce-doped CN nanosheets showed improved photocatalytic activities under visible light irradiation, with NiCe-CN showing the best performance with 98% conversion after 2.5 h, and product selectivity exceeding 99% in light-driven amine-imine oxidation reactions. Radical trapping experiments reveal the importance of generating h⁺, ¹O₂, and \(\cdot {\text{O}}_{2}^{ - }\) $·{\text{O}}_2^{-}$ for photocatalytic conversion of substrates, with relevant catalytic mechanisms presented. This study provides a crucial reference for designing and synthesizing novel bimetallic co-doped g-C₃N₄ photocatalytic materials to enhance photocatalytic organic synthesis reactions.