Interfacial chemical bond reinforced S-scheme heterojunction of perylene diimide and nitrogen-deficient carbon nitride toward efficient charge transfer and high-performance CO2 photoreduction.

Developing high-efficiency carbon nitride (CN) based photocatalysts is central to sunlight-powered CO2 photoreduction, yet real-world application is constrained by severe bulk charge recombination and large interfacial transport barriers at heterojunction boundaries. Against this backdrop, we report an all-organic covalently bonded S-scheme heterojunction photocatalyst that resolves these limitations via the synergy of nitrogen-vacancy engineering and built-in electric-field (IEF) modulation. Highly crystalline perylene diimide (PDI) is covalently coupled with nitrogen-deficient carbon nitride (NV-CN) through interfacial CN linkages to form an intimate heterointerface. Benefiting from the combined effect of interfacially generated IEF and in-situ introduced nitrogen vacancies, photogenerated electrons are efficiently trapped and carriers are steered along directional migration pathways, markedly suppressing electron-hole recombination and diminishing interfacial charge-transport resistance. Experimental evaluations confirm that the optimized NV-CN-PDI5.0 catalyst delivers exceptional CO2 photoreduction performance with a CO production rate of 37.86 ± 1.04 μmol g-1 h-1, far exceeding pristine CN and its physically blended counterparts. Supported by density functional theory (DFT) calculations, the synergistic enhancement originating from defective sites and S-scheme charge-transfer dynamics is systematically elucidated. This work affords an instructive route toward the rational design of high-performance all-organic S-scheme heterojunction photocatalysts.