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 Cβ 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.