Boosted Charge Transfer Efficacy of an All‐Solid‐State Z‐Scheme BiOI‐CD‐CdS Photocatalyst for Enhanced Degradation of 4‐Nitrophenol and Oxidation of Benzyl Alcohol under Visible Light**

Abstract Recently, utilization of solar light for chemical reactions has become a popular approach. Inspired by nature, we fabricated a ternary system, BiOI‐CD‐CdS, which is more durable and shows multiple photocatalytic applications. The incorporated carbon dots (CD) serve as a solid‐state electron mediator and Z‐scheme facilitator. The material was employed for photooxidative degradation of 4‐nitrophenol (a pollutant) and selective oxidation of benzyl alcohol into the corresponding aldehyde in an acetonitrile medium. In this study, 10 wt % BiOI‐CD‐CdS (denoted as 10 wt % BCC) shows the highest photocatalytic performance compared to the individual semiconductors BiOI and CdS, and gave a degradation rate constant ( k ) of 12.67×10 −3 min −1 (4‐nitrophenol), which is 17.5 times and 6.5 times higher than its individual components. Moreover, the catalyst offers a 90 % conversion of benzyl alcohol to benzaldehyde with high selectivity (98 %). Directed by mechanistic insight, the charge transfer process was observed between BiOI and CdS, where CD serves as an electron mediator/charge separator. The radicals formed by the photocatalysis are superoxide (O 2 .− ), hydroxyl radicals ( . OH), and holes (h + ). The intermediates and mechanistic pathways were traced using HPLC, GC‐MS, and EPR studies. Moreover, the work demonstrated a smart strategy for designing a ternary Z‐scheme photocatalytic system, which could be useful for environmental decontamination and selective organic transformation under visible light.