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 (TF 50 -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 TF 50 -COF, resulting in improved crystallinity with faster carrier transfer and robust photostability. The TF 50 -COF catalyst demonstrates high selectivity and stability in O 2 photoreduction into H 2 O 2 , with a high H 2 O 2 yield rate of 1739 μmol 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.