Triphenylene-Derived Polyimide Covalent Organic Frameworks for Efficient Photosynthesis of Hydrogen Peroxide

Photocatalytic hydrogen peroxide (H₂O₂) production offers a sustainable route for on-demand generation. Covalent organic frameworks (COFs) are attractive candidates, as their modular architectures can be engineered for optimal light capture and charge separation. However, their practical use has been hindered by the limited chemical stability of imine-linked COFs under prolonged operation. This challenge is further compounded by the narrow selection of building blocks suitable for efficient H₂O₂ generation, restricting advancements in catalytic performance. Here, we present two polyimide-based COFs (NUS-76 and NUS-77) constructed with a newly designed fused-ring triphenylene building block, enabling efficient photocatalytic H₂O₂ production. Utilizing a simple water-assisted microwave synthesis, both COFs exhibit remarkable robustness, retaining their crystalline structure even in strongly acidic and alkaline environments, outperforming the established imine-linked COF. Remarkably, NUS-77 integrates triphenylene and oligo(phenylenevinylene) moieties, delivering an impressive photocatalytic H₂O₂ evolution rate up to 23,284 μmol g^-1 h^-1. To further showcase their practical potential, we developed a continuous-flow photoreactor incorporating NUS-77, which produces 40.7 mM H₂O₂ in 9 h and retains activity over four consecutive cycles (36 h) under 1 sun irradiation (P = 100 mW cm^-2), a product concentration exceeding that of most reported COF photocatalysts. Theoretical calculations reveal that the imide linkage enhances charge separation and facilitates the formation of ·O₂^- intermediates during the catalytic redox cycle. Together, these findings illustrate how strategic engineering of linkages and building blocks effectively overcomes the stability limitations of COF-based photocatalysts, providing a viable pathway to durable frameworks for solar-to-chemical energy conversion.