20:T479,Hydrogen peroxide (H₂O₂) is one of the most important industrial oxidants. In principle, photocatalytic H₂O₂ synthesis from oxygen and H₂O using sunlight could provide a cleaner alternative route to the current anthraquinone process. Recently, conjugated organic materials have been studied as photocatalysts for solar fuels synthesis because they offer synthetic tunability over a large chemical space. Here, we used high-throughput experiments to discover a linear conjugated polymer, poly(3-4-ethynylphenyl)ethynyl)pyridine (DE7), which exhibits efficient photocatalytic H₂O₂ production from H₂O and O₂ under visible light illumination for periods of up to 10 h or so. The apparent quantum yield was 8.7% at 420 nm. Mechanistic investigations showed that the H₂O₂ was produced via the photoinduced stepwise reduction of O₂. At longer photolysis times, however, this catalyst decomposed, suggesting a need to focus the photostability of organic photocatalysts, as well as the initial catalytic production rates.21:T535,The highly oxygen-dependent nature of photodynamic therapy (PDT) limits its therapeutic efficacy against hypoxic solid tumors in clinics, which is an urgent problem to be solved. Herein, we develop an oxygen-independent supramolecular photodynamic agent that produces hydroxyl radical (^•OH) by oxidizing water in the presence of intracellularly abundant pyruvic acid under oxygen-free conditions. A fluorene-substituted BODIPY was designed as the electron donor and coassembled with perylene diimide as the electron acceptor to form the quadruple hydrogen-bonded supramolecular photodynamic agent. Detailed mechanism studies reveal that intermolecular electron transfer and charge separation upon light irradiation result in an efficient generation of radical ion pairs. Under oxygen-free conditions, the cationic radicals directly oxidize water to generate highly cytotoxic ^•OH, and the anionic radicals transfer electrons to pyruvic acid, realizing the catalytic cycle. Thus, this photodynamic agent exhibited superb photocytotoxicity even under severe hypoxic environments and excellent in vivo antitumor efficacy on HeLa-bearing mouse models. This work provides a strategy for constructing oxygen-independent photodynamic agents, which opens up an avenue for effective PDT against hypoxic tumors.

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