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

An all-organic S-scheme NV-CN-PDI 5.0 heterojunction was successfully fabricated. • The improved yield can be attributed to the synergistic effect of nitrogen vacancies and the S-scheme heterojunction. • The CO yield of NV-CN-PDI 5.0 reached 37.06 μmol g −1  h −1 , 5.5 times that of pristine CN. • Photocatalytic mechanism is elucidated by experiments and calculations. Developing high-efficiency carbon nitride (CN) based photocatalysts is central to sunlight-powered CO 2 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 (N V -CN) through interfacial C N 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 N V -CN-PDI 5.0 catalyst delivers exceptional CO 2 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. By bridging N V -CN with PDI, a covalently bonded S-scheme N V -CN-PDI 5.0 heterojunction is constructed. The internal built-in electric field and C − N covalent bonds synergistically serve as charge transport pathways to accelerate charge migration and separation, thereby distinctly boosting the photocatalytic CO 2 reduction performance. Download: Download high-res image (124KB) Download: Download full-size image