Visible-Light-Driven Photocatalysis of Carbon Dioxide and Organic Pollutants by CaBiO₂Cl/g-C₃N₄

Perovskite-type CaBiO₂Cl with a unique layered Sillen X1 structure exhibits great potential as an efficient visible-light photocatalyst. In this study, CaBiO₂Cl was synthesized through calcination at 800 °C and subsequently composited with varying amounts of g-C₃N₄ to optimize photocatalytic performance. The prepared catalysts were characterized by multiple techniques to confirm their structural and compositional features. Under visible-light irradiation, the photocatalytic activities toward Rh6G degradation were systematically evaluated using UV-vis PDA and EPR analyses. To further elucidate the degradation mechanism, radical scavenger experiments were conducted to identify the reactive species generated during the photodegradation process. Kinetic analysis revealed that the reaction rate constant (k) of pure CaBiO₂Cl was 0.0525 h^-1, while that of pure g-C₃N₄ was 0.0423 h^-1. Notably, the CaBiO₂Cl/10 wt% g-C₃N₄ composite exhibited an enhanced k value of 0.0568 h^-1, which is 1.1 and 1.3 times higher than those of CaBiO₂Cl and g-C₃N₄, respectively. Furthermore, under ambient conditions (25 °C, 1 atm), the CO₂-to-CH₄ photocatalytic conversion efficiency of the CaBiO₂Cl/10 wt% g-C₃N₄ composite reached 0.5652 μmol g^-1 h^-1. These findings demonstrate that CaBiO₂Cl-based composite photocatalysts not only achieve superior visible-light photocatalytic activity but also exhibit excellent stability, highlighting their potential for environmental remediation and alignment with the principles of green chemistry.