Covalent Organic Cage-Based Photocatalysts for Highly Efficient and Selective H₂O₂ Production.

Abstract

Photocatalysts are key to sustainable hydrogen peroxide (H₂O₂) production, yet most reported systems are polymeric or composite, with limited solubility and poorly defined architectures that obscure mechanistic understanding and structure-function relationships. Here we present covalent organic superphane cages bearing secondary amine, tertiary amine, or ammonium functionalities as discrete, metal-free photocatalysts for H₂O₂ generation. Among them, the tied tertiary amine derivative (SUPE-ptz-2) exhibits enhanced light absorption, efficient charge carrier separation and transfer, and precisely organized redox-active sites. As a result, SUPE-ptz-2 achieves an H₂O₂ production rate of 11,089 µmol h^- ¹ g^- ¹ in oxygen-saturated water, rising to 25,031 µmol h^- ¹ g^- ¹ with 10% isopropanol, with an apparent quantum yield of 29.2% at 400 nm and 93% selectivity for the two-electron oxygen reduction pathway. Comprehensive experimental investigations combined with density functional theory calculations reveal that phenothiazine moieties facilitate water oxidation via the four-electron WOR pathway, while amine groups promote oxygen reduction through both the two-electron ORR1 and ORR2 pathways; the tied cage architecture enforces spatial separation of redox sites, stabilizes key reaction intermediates, and enhances charge transport. Beyond photocatalytic efficiency, SUPE-ptz-2 demonstrates robustness across diverse water sources and enables sunlight-driven disinfection. These results establish covalent-organic superphane cages as photocatalysts (singzymes) for sustainable H₂O₂ generation and broaden their potential in solar-to-chemical energy conversion and environmental applications.