Abstract: Photocatalytic H₂O₂ synthesis is commonly dominated by the oxygen reduction reaction (ORR), whereas simultaneously enabling water oxidation reaction (WOR) and directional charge separation through band-structure regulation remains challenging. Herein, sulfur doping and pyridine modification were integrated to construct an intramolecular donor-π-acceptor (D-π-A) network within the carbon nitride framework. The resulting electronic polarization promotes directional separation of photogenerated charge carriers and optimizes the band structure to thermodynamically enable both ORR and WOR pathways. Consequently, the as-synthesized SCN-AP photocatalyst achieves an H₂O₂ yield of 1030 μmol g^-1 within 2 h in pure water, 3.73 times that of pristine PCN, and exhibits effective antibacterial activity against clinically relevant pathogens including Acinetobacter beijerinckii and Klebsiella variicola. The in situ electron paramagnetic resonance (EPR) spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) collectively support the coexistence of ORR and WOR pathways. The ORR serves as the predominant route and involves a ·O₂^--mediated stepwise reduction pathway together with a ¹O₂- associated pathway, while WOR provides a complementary hole-driven contribution to H₂O₂ formation. This work demonstrates a feasible band-engineering strategy for constructing polymeric photocatalysts with directional charge transfer and dual-pathway H₂O₂ photosynthesis.

Key words: Carbon nitride, D-π-A network structure, Dual-pathway reactions, H₂O₂ Photosynthesis, Antibacterial activity