Construction of sulfur-chloride co-doped triazine/heptazine homojunction carbon nitride photocatalyst for simultaneous production of H2O2 and lignin C-C bond cleavage

Photocatalytic H₂O₂ production and cleavage of lignin C-C bonds is a typical strategy that follows sustainable development. Unfortunately, the photocatalytic efficiency of these two reactions still faces significant challenges. Herein, a carbon nitride photocatalyst (tri/hep-CN) with sulfur-chloride co-doped triazine and heptazine structures was synthesized. It was simultaneously used for photocatalytic H₂O₂ production and lignin C-C bond cleavage. In the air atmosphere, the yield of H₂O₂ reached 1171.9 μmol•g⁻¹•h⁻¹ after the addition of β-1 lignin model 1,2-diphenylethanol (Dpol) to the solvent. The yield of H₂O₂ increased by 20 times compared with no addition of Dpol. The lignin C-C bond in Dpol is also efficiently broken, producing benzaldehyde and benzyl alcohol. tri/hep-CN has excellent photogenerated carrier separation efficiency and positive valence potential, which improves the photocatalytic H₂O₂ production and lignin C-C bond cleavage performance. Notably, coupling photocatalytic H₂O₂ production with lignin C-C bond cleavage to fully use photogenerated electrons and holes is also very important to obtain outstanding photocatalytic performance. Mechanistic studies have shown that photocatalytic H₂O₂ production follows an indirect reaction mechanism. Meanwhile, the cleavage of lignin C-C bond follows the C_β radical mechanism and the single electron transfer mechanism. This work is very instructive for simultaneous photocatalytic H₂O₂ production and lignin C-C bond cleavage studies.