Substituting the phenyl with alkynyl in donor unit over donor-acceptor covalent triazine frameworks for superior photosynthesis of hydrogen peroxide.

Covalent organic frameworks (COFs) have been emerged as a kind of promising photocatalysts for the artificial synthesis of HO, but the efficiency is largely limited by the subpar transport of photogenerated carriers and sluggish surface O reduction process. Here, via tuning the functional group of donor monomer from phenyl into alkynyl group, two donor-acceptor (D-A) type covalent triazine frameworks (BT-COF and TT-COF) were synthesized, of which the triazine moiety acted as the principal active center for O reduction. Due to the high-density electrons of alkynyl group, experimental results revealed that the BT-COF catalyst owned the facilitated O adsorption and superior charge transportation, in addition to more negative reduction potential. Accordingly, the BT-COF catalyst exhibited relatively a high photocatalytic HO production rate (7200 μmol h g) under visible light irradiation, about 1.5 times of the TT-COF catalyst. The wavelength-dependent apparent quantum yield test verified that the HO production over the BT-COF catalyst was the semiconductor-based photocatalysis. In-situ FTIR spectra further confirmed that the HO generation went through a two-step single-electron O reduction route, in which •O existed as intermediate. This study provides insights into the superior O conversion for HO photosynthesis over D-A COFs by optimizing the functional groups of donor monomers.