Artificial photocatalysis offers a clean approach for producing H2O2. However, the poor selectivity and activity of H2O2 production hamper traditional industrial applications and emerging photodynamic therapy (PDT)/chemodynamic therapy (CDT). Here, we report a well-defined C5N2 photocatalyst with a conjugated C=N linkage for highly selective and efficient non-sacrificial H2O2 production both in normoxic and hypoxic systems. The strengthened delocalization of π-electrons by linkers in C5N2 significantly downshifted the band position, which eliminated the side photoreduction reaction of H2 evolution in thermodynamics and promoted water oxidation ability in kinetics. As a result, C5N2 had a competitive overall H2O2 production with solar-to-chemical conversion efficiency of 0.55% and more interestingly, exhibited the highest activity so far in hypoxic condition (698 μM/h). C5N2 was further applied to hypoxic PDT/CDT, exhibiting outstanding performance in conspicuous cancer cell death and synchronous bioimaging. It shed light on unlocking linker functions in electronic structure engineering of carbon nitrides for highly efficient overall photosynthesis of H2O2 and expanded the scope of their prospective application in health care.
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