All-organic covalent organic frameworks/perylene diimide urea polymer S-scheme photocatalyst for boosted H2 generation

Conjugated covalent organic frameworks (COFs) hold great promise in photocatalytic hydrogen evolution owing to their high crystallinity, large surface area, and distinct structure. However, COFs exhibit poor charge separation. Therefore, investigating highly effective COF-based photocatalysts is crucial. For the first time, conjugated COF/perylene diimide urea polymer (PUP) all-organic heterostructure with S-scheme interfacial charge-transfer channels was successfully developed and manufactured via in situ coupling of the two-dimensional triazine-based imine-linked COF (denoted as TATF-COF) with PUP. The optimal photocatalytic hydrogen-evolution rate of 94.5 mmol h−1 g−1 for TATF-COF/PUP is 3.5 times that of pure TATF-COF and is comparable to or even higher than that of the previously reported COF-based photocatalysts, resulting in an apparent quantum efficiency of up to 19.7% at 420 nm. The improved directional S-scheme charge transfer driven by the tuned built-in electric field and enhanced oxidation and reduction reaction rates of the photogenerated carriers contribute synergistically to the boosted photocatalytic H2 evolution. Experiments and theoretical studies reveal plausible H2 evolution and spatial S-scheme charge-separation mechanisms under visible-light irradiation. This study provides advanced methods for constructing all-organic S-scheme high-efficiency photocatalysts by the modulation of band structures.