Extended Conjugation Tuning Carbon Nitride for Non‐sacrificial H₂O₂Photosynthesis and Hypoxic Tumor Therapy**

Abstract

Artificial photocatalysis offers a clean approach for producing H 2 O 2 . However, the poor selectivity and activity of H 2 O 2 production hamper traditional industrial applications and emerging photodynamic therapy (PDT)/chemodynamic therapy (CDT). Herein, we report a C 5 N 2 photocatalyst with a conjugated C=N linkage for selective and efficient non-sacrificial H 2 O 2 production in both normoxic and hypoxic systems. The strengthened delocalization of π-electrons by linkers in C 5 N 2 downshifted the band position, thermodynamically eliminating side H 2 evolution reaction and kinetically promoting water oxidation. As a result, C 5 N 2 had a competitive solar-to-chemical conversion efficiency of 0.55 % in overall H 2 O 2 production and exhibited by far the highest activity under hypoxic conditions (698 μM h À 1 ). C 5 N 2 was further applied to hypoxic PDT/ CDT with outstanding performance in apparent cancer cell death and synchronous bioimaging. The study sheds light on the photosynthesis of H 2 O 2 by carbon nitrides for health applications.