Homologous heteropolyaromatic covalent organic frameworks for enhancing photocatalytic hydrogen peroxide production and aerobic oxidation

Synthesis and characterization of COFs

We initiated our synthesis with the imine-based TTI-COF, prepared via solvothermal condensation of tris(4-formylphenyl) triazine and tris(4-aminophenyl) triazine (see the Methods for details). After a reaction for 72 hours at 120 °C, a yellowish powder was obtained, representing the TTI-COF (Fig. 1a). The subsequent step involved the transformation of TTI-COF into a thiazole-based homologous heteropolyaromatic COF (TTT-COF) through a post-cyclization reaction with elemental sulfur. This process commences with the oxidation of aromatic imines by sublimated sulfur vapor at 350 °C, yielding thioamides, which then undergo an oxidative cyclization reaction to form thiazole rings (Supplementary Fig. 1)⁷⁸. Here, molecular sulfur (S₈) dually functions as an oxidizing agent and a nucleophile, initially binding to the imine carbon and subsequently to the phenyl ring adjacent to the nitrogen of…