Sulfone site enables H2O2 practical fabrication over metal-free photocatalyst

The photocatalytic synthesis of hydrogen peroxide (H 2 O 2 ) from water and oxygen offers a sustainable route to replace the energy-intensive anthraquinone process. However, the practical application of this technology is hindered by the prevalent issues of ambiguous active sites, elusive reaction mechanisms, and insufficient efficiency in conventional photocatalysts. Herein, we address these challenges by designing a metal-free porous organic polymer, PA-BTDO, featuring well-defined sulfone-based dual‑oxygen sites (O=S=O). This catalyst achieves an exceptional H 2 O 2 production rate of 2090 μmol g −1 h −1 under visible light, ranking among the highest for metal-free systems. Notably, we demonstrate the scalable production of a 1.0 wt% H 2 O 2 solution—directly applicable for medical use—from a laboratory-scale system using merely 1.0 g of catalyst over 24 h. Mechanistic investigations reveal that the dual‑oxygen sites undergo a concerted photochemical transformation into two adjacent S-O-H groups, which synergistically adsorb O 2 via a Yeager-type mode and stabilize a novel seven-membered ring transition state. This unique configuration drastically lowers the reaction barrier, enabling highly efficient H 2 O 2 generation. This work not only establishes a pioneering strategy for active-site design via transition-state engineering but also opens a practical pathway for solar-driven H 2 O 2 production. Herein, we designed a sulfone-based porous organic polymer (PA-BTDO) featuring innovative dual‑oxygen active sites (O=S=O), which drives efficient photocatalytic H 2 O 2 generation via a well-defined mechanism involving O=S=O to S-O-H site transformation, Yeager-type O 2 activation, and a decisive seven-membered ring transition state formation. • A sulfone-based polymer (PA-BTDO) with dual-oxygen sites (O=S=O) is designed for efficient H 2 O 2 photosynthesis from H 2 O and O 2 under visible light, enabling practical application. • The PA-BTDO enables the practical synthesis of 1.0 wt.% H 2 O 2 solution using only 1.0 g of catalyst in 24 h, meeting the standard for medical use. • The PA-BTDO photocatalyst clarifies the seven-membered ring transition state mechanism via its well-defined dual-oxygen sites, overcoming the ambiguity of mono-oxygen-site systems. • The PA-BTDO provides a novel metal-free design strategy by engineering reaction transition states to achieve efficient solar-driven H 2 O 2 synthesis.