Quantum dot-based photocatalysts for CO2 valorisation in organic transformations.

The conversion of CO2 into value-added chemicals represents one of the most compelling challenges in contemporary sustainable chemistry. Quantum dots (QDs)-colloidal semiconductor nanocrystals positioned at the interface of homogeneous and heterogeneous catalysis-offer a uniquely versatile platform to address this challenge. Their size-tunable bandgaps, high absorption cross-sections, versatile surface chemistry, coupled with distinct photophysical phenomena, provide opportunities for photocatalytic transformations that are difficult to achieve with traditional molecular photocatalysts. In this review, we survey recent advances in QD-driven photocatalytic systems for coupled CO2 reduction and selective organic oxidation, cascade CO2 conversion, and direct CO2 incorporation into value-added organic molecules. We discuss the thermodynamic and kinetic principles governing CO2 activation, the distinctive photophysical properties of QDs relevant to catalysis, and the role of surface ligand engineering in controlling charge transfer and reaction selectivity. Key reactions include integrated cooperative systems coupling CO2 reduction with alcohol or amine oxidation, oxidative coupling, and plastic waste valorization, carboxylation, enantioselective amino acid synthesis, and cyclic carbonate synthesis from CO2 and epoxides. Future directions including in situ characterisation, toxic metal-free QD development, scope expansion, and scalable continuous-flow systems are discussed.