Rational design of WO3-modified ultrathin Cl-C3N4 step-scheme heterojunctions for enhanced removal of organic contaminants: Performance, pathways, and toxicological assessment

To address the escalating concerns related to organic pollutions in aquatic environments, there is an urgent demand for exploring an efficient and eco-friendly method for the removal of organic pollutants. In this work, porous Cl-C 3 N 4 (ClCN)and step-scheme (S-Scheme) Cl-C 3 N 4 /WO 3 (ClCN/WO 3 ) composites have been designed and fabricated through a facile calcination approach for tetracycline removal under visible-light irradiation. The synthesized S-Scheme ClCN/WO 3 composites exhibited porous structures, though their visible-light absorption was lower compared to the ClCN and C 3 N 4 samples. The surface areas of the ClCN/WO 3 composites can reach 81.43 m 2 g −1 , significantly higher than that of the ClCN and C 3 N 4 samples. These composites also demonstrated prolonged carrier lifetime and improved charge separation efficiency, primarily due to the formation of S-Scheme heterostructures. Among the prepared samples, the ClCN/WO 3 -2 composite demonstrated the highest photocatalytic activity with a rate constant reaching 0.0547 min −1 , approximately 4.56 times that of pristine C 3 N 4 . Additionally, when applied to tetracycline degradation in simulated seawater, the ClCN/WO 3 -2 composite achieved a rate constant of 0.047 min −1 , outperforming the C 3 N 4 and ClCN samples. Mechanistic studies showed that the S-Scheme heterostructures markedly promoted charge separation and tetracycline degradation. Furthermore, the ClCN/WO 3 composites contributed to a reduced the biological toxicity of the degraded intermediates. This study underscores the immense potential of ClCN/WO 3 composites as high-performance photocatalysts for the photodegradation of organic pollutants under visible-light irradiation.