Synthesis of sp²-Carbon Covalent Triazine Framework Photocatalysts for Efficient Organic Dye Degradation

A novel sp²-carbon covalent triazine framework (sp²-CTF) was synthesized via a ternary solvent system with equimolar amounts of 2,4,6-trimethyl-1,3,5-triazine and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine as precursors. The temporal evolution of its physicochemical properties was systematically investigated, revealing that an optimal structural configuration of sp²-CTF₇₂ was achieved through solvothermal treatment at 120 °C for 72 h. Under visible light irradiation, sp²-CTF₇₂ achieved 87.71% decolorization of methyl orange (MO) within 90 min using a catalyst loading of 0.3 g/L, an initial MO concentration of 10 mg/L, and pH 6.5. Notably, under comparable conditions, 99.80% of methylene blue (MB) was degraded within 30 min. This exceptional photocatalytic activity is attributed to an elongated fibrous morphology, which promotes efficient migration of photogenerated charge carriers. Intermediate products identified during MO degradation provided insight into the photocatalytic degradation pathway. Mechanistic studies revealed a synergistic effect between superoxide radicals (^•O₂^-) and hydroxyl radicals (^•OH), with ^•O₂^- serving as the predominant active species. In contrast, direct oxidation by photogenerated holes was found to inhibit catalytic activity, underscoring the crucial role of ^•O₂^--mediated pathways in the photocatalytic process.