Photocatalytic H₂O₂ production from water and air using porous organic polymers

Producing hydrogen peroxide (H₂O₂) from H₂O and O₂ under visible light irradiation is a promising solar-to-chemical energy conversion technology. Hydrogen peroxide has versatile applications as a green oxidant and liquid energy carrier but has been produced through energy-intensive and complex anthraquinone processes. Herein, we report the rational design of efficient and stable porous organic polymer (POP) containing redox centers, anthraquinone photocatalyst (ANQ-POP) for solar H₂O₂ production. ANQ-POP is readily synthesized with stable dioxin-linkages via efficient one-pot, transition-metal-free nucleophilic aromatic substitution reactions between 1,2,3,4,5,6,7,8-octafluoro-9,10-anthraquinone (OFANQ) and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP). Exhibiting a fibrillar morphology, ANQ-POP boasts a high surface area of 380 m²∙g^-1 and demonstrates thermal stability. With 10 % ethanol, ANQ-POP yields an H₂O₂ production rate of 320 μmol g^-1 under visible light irradiation. Moreover, ANQ-POP alone can efficiently produce H₂O₂ without any photosensitizers and cocatalysts. Density functional theory calculations reveal that the quinone groups of the anthraquinone moieties can serve as redox centers for H₂O₂ production under light irradiation. Furthermore, unlike most conventional photocatalysts, it can produce H₂O₂ using only water and air by catalyzing both oxygen reduction and evolution reactions under light irradiation. Our findings provide an efficient, eco-friendly pathway for photocatalytic production of H₂O₂ under mild reaction conditions using a dioxin-derived POP-based photocatalyst.