Electron-Deficient Engineering in Large-Conjugate-Heptazine Framework to Effectively Shuttle Hot Electrons for Efficient Photocatalytic H2O2 Production

Abstract

Photocatalytic oxygen reduction to H₂O₂ based on g-C₃N₄ has presented promising potential for sustainable solar-fuel production. Yet tuning the timescale of hot electron's lifetime to effectively participate in the surface reactions remains challenging. Here, an electron-deficient engineering strategy is developed by incorporating an electron-deficient structure (EDS) with different conjugate regions into large conjugate-heptazine framework (LCHF) of g-C₃N₄ to steer hot electrons of the different timescales to effectively activate O₂ for efficient photocatalytic H₂O₂ production. Femtosecond transientabsorption spectroscopy reveals that introducing EDS into LCHF can steer hot electron rapid transfer to the trapping sites of EDS and notably eliminate the deeply trapped electrons as well as enhance the shallow capture. It is demonstrated that pyromellitic dianhydride not only can tune the lifetime scale of hot electrons but also provide nonpolarized active sites to effectively activate O₂ forming H₂O₂ with lower energy barrier via direct or stepwise 2e⁻ pathways. This photocatalyst achieves an H₂O₂ yield rate of 25.40 mmol g⁻¹ h⁻¹, enabling an apparentquantumyield of 45.7% at 400 nm and a solar-to-chemical efficiency of 2.63%, outperforming the other reported photocatalysts. This work will shed light on the design of organic photocatalysts to tune hot electrons to effectively engage in the surface reaction.