A Crystalline Partially Fluorinated Triazine Covalent Organic Framework for Efficient Photosynthesis of Hydrogen Peroxide

A partially fluorinated, metal-free, imine-linked two-dimensional triazine covalent organic framework (TF50-COF) photocatalyst was developed. Fluorine (F)-substituted and nonsubstituted units were integrated in equimolar amounts on the edge aromatic units, where they mediated two-electron O-2 photoreduction. F-substitution created an abundance of Lewis acid sites, which regulated the electronic distribution of adjacent carbon atoms and provided highly active sites for O-2 adsorption, and widened the visible-light-responsive range of the catalyst, while enhancing charge separation. Varying the proportion of F maximized the interlayer interactions of TF50-COF, resulting in improved crystallinity with faster carrier transfer and robust photostability. The TF50-COF catalyst demonstrates high selectivity and stability in O-2 photoreduction into H2O2, with a high H2O2 yield rate of 1739 mu mol h(-1) g(-1) and a remarkable apparent quantum efficiency of 5.1 % at 400 nm, exceeding the performance of previously reported nonmetal COF-based photocatalysts.