A novel organic/inorganic S-scheme heterostructure of TCPP/Bi₁₂O₁₇Cl₂ for boosting photodegradation of tetracycline hydrochloride: Kinetic, degradation mechanism, and toxic assessment

The exploration of environment-friendly and efficacious materials with eminent photocatalytic efficacy is critical for the elimination of pharmaceutical antibiotics. Herein, a visible-light-driven organic-inorganic S-scheme heterostructure of meso-tetra (4-carboxyphenyl) porphyrin (TCPP)/Bi12O17Cl2, aiming to wipe out the antibiotic in wastewater, is developed via a simple approach. The TCPP is anchored on the surface of Bi12O17Cl2 to create the S-scheme junction between TCPP and Bi12O17Cl2, which strengthens visible-light response and expedites the spatial disintegration and conservation of photo-carriers with high redox capacity, therefore leading to a significant reinforcement of the photo-activity and stability. The champion TCPP/Bi12O17Cl2 manifests the best photo-degradation efficiency of 79.4% with the photoreaction rate constant of 0.0125 min-1 for tetracycline elimination, being 2.6 folds that of Bi12O17Cl2. The involved crucial reactive radicals, photo-degradation pathway and mechanism, and the eco-toxicity of intermediates over TCPP/Bi12O17Cl2 were elucidated through scavenging tests, LC-MS analysis, and toxicity calculation. This research illustrates the potential practicability on the rational design of porphyrin-based S-scheme heterojunction photocatalysts for efficient anti-biotic removal.