Construction of g-C3N4@Bi-MOF@BiOCl double Z-type heterojunctions for photodegradation of antibiotics under visible light irradiation: Mechanism, pathway, and toxicity assessment

In this study, flower-like microspheres dispersed double Z-type heterojunction g-C3N4@Bi-MOF@BiOCl photocatalysts were prepared using Bi-MOF as the structural template. The photocatalyst showed good degradation ability for both tetracycline antibiotics under simulated sunlight irradiation, as well as stable recyclability and total organic carbon mineralization (TOC). This excellent photocatalytic activity was mainly attributed to the formation of double Z-type heterojunctions that accelerated charge separation and transfer and drove stronger redox capacity. In addition, the effects of conditions such as catalyst dosage, initial concentration of tetracycline hydrochloride (TC) and initial pH (3-11) value of the solution on the photocatalytic reaction were investigated. The results of free radical trapping experiments and ESR analyses indicated that center dot O-2(-), h(+) and center dot OH were the active free radicals that could not be neglected for the degradation of tetracycline hydrochloride (TC), and a possible degradation mechanism was further proposed. Finally, the possible pathways for degradation of the intermediates were rationally deduced by gas chromatography (GC-MS) and evaluated by ecotoxicity analysis based on the utilization rate (T.E.S.T.) of the intermediates produced. This study provides an effective idea for the rational design and synthesis of highly efficient dual Z-type photocatalysts for antibiotic contamination in water-polluted environments.