Redox-Mediated TEMPO-Based Donor-Acceptor Covalent Organic Framework for Efficient Photo-Induced Hydrogen Peroxide...

Molecular engineering of covalent organic frameworks (COFs) offers an alternative approach to conventional anthraquinone oxidation via photo-induced H₂O₂ production from O₂ reduction. Despite their potential, reported photocatalysts suffer limited proton mobility, low selectivity, and insufficient charge separation and utilization. Herein, we report a nitroxyl radical (TEMPO) decorated two-dimensional (2D) donor-acceptor (D-A)-COF photocatalyst via a one-pot strategy. Under visible light irradiation, highly crystalline TAPP-TPDA-TEMPO-COF (TT-T-COF) exhibits a remarkable photocatalytic H₂O₂ yield of 10066 μmol g^-1 h^-1 in two-phase water-benzyl alcohol (10 % BA) system through direct two-electron (2e^-) pathway. The mechanistic study by DFT calculations and in situ DRIFT spectra suggests Yeager-type adsorption of *O₂⋅^- intermediate on the nitroxyl radical site (N-O⋅). The efficient photocatalytic performance and stability of TT-T-COF are attributed to the involvement of the nitroxyl radical, which enhances selective O₂ adsorption, establishes a distinct electron density distribution, and facilitates photogenerated charge separation compared to TT-HT-COF and TT-COF counterparts. This study uncovers a new perspective for constructing metal-free, redox-mediated radical-based COFs for sustainable energy conversion, storage, and biomedical applications.