Heavy-Metal-Free Colloidal Quantum Dots for Photocatalysis

Heavy-metal-free colloidal quantum dots (QDs) have emerged as promising photocatalysts for solar-to-chemical conversion because they combine low toxicity, tunable band structures, strong light absorption, and engineerable surfaces/interfaces. Recent advances across InP, zinc chalcogenides, and Cu-/Ag-based I-III-VI nanocrystals have expanded the design space from simple composition control to core/shell engineering, alloying, anisotropic growth, ligand regulation, and hybrid-interface construction. These strategies enable precise control over band alignment, trap states, charge separation, and interfacial transfer, which collectively govern photocatalytic activity and selectivity. This review summarizes recent progress in heavy-metal-free colloidal QDs for photocatalysis, with emphasis on representative material families, key structural engineering approaches, and common synergistic mechanisms, including band alignment engineering, defect/trap-state regulation, and pathway-directed interfacial charge transfer. Representative applications and current challenges are also discussed to provide guidance for the rational design of next-generation sustainable photocatalysts.