<p>Photocatalysis is an effective method to achieve harmless treatment of antibiotic wastewater. The g-C₃N₅ usually had a high photoelectron-hole complex, which greatly limited the photocatalytic performance. It was investigated that the TiO₂/g-C₃N₅ heterojunctions were prepared by the strategy of constructing heterojunctions, and the S scheme charge transfer mechanism retained highly active electrons and holes. The bending of the energy bands and the establishment of the internal electric field (IEF) drive the charge transfer from TiO₂ to g-C₃N₅ through the bent energy bands. The construction of heterojunction enables the spectral absorption to be effectively broadened, the photoelectron-hole separation to become highly efficient, and the generation of highly reactive radicals to realize the efficient removal of antibiotics from wastewater. After visible light irradiation for 30&#xa0;min, the TiO₂/g-C₃N₅ (1:2) showed excellent photocatalytic activity, and the degradation rate of sulfamethylthiazole (STZ) reached 98.8%. STZ was degraded to small inorganic molecules such as H₂O, CO₂ and inorganic acids by a complex bond-breaking hydroxylation reaction under the attack of reactive groups such as ·O₂⁻,·OH and h⁺. The S-scheme charge transfer mechanism of TiO₂/g-C₃N₅ heterojunction material was proposed through band potential analysis and density functional theory (DFT) calculation.</p>