Boosting CO₂ Photoreduction through Dispersing Quantum Dots in Viscous Polymer Networks

Natural photosynthesis, which achieves high photo-to-chemical conversion efficiency, operates in a highly viscous environment rich in biopolymers that effectively promote charge separation. Inspired by this biological strategy, we explored artificial photoreduction of CO₂ within viscous polymer networks. Specifically, quantum dots (QDs)─functioning as both light-harvesting antennas and catalytic centers─were embedded into physically cross-linked poly(vinyl alcohol) (PVA) gel networks. Under visible-light irradiation, QDs embedded in PVA gel networks exhibited markedly enhanced activity for CO₂-to-CO conversion, achieving ≈94.9 mmol per gram of QDs per hour (mmol g^-1 h^-1)─among the highest values reported for QD-based photocatalytic systems. Mechanistic studies suggested that S^2- capped QDs interact with the semicrystalline PVA networks via hydrogen bonding, which facilitates hole trapping of the photogenerated charges on the QDs. Furthermore, coembedding plasmonic Au nanocrystals (NCs) with QDs in the same gel networks enabled the coupling of proton reduction with CO₂ reduction, leading to the efficient production of syngas (CO and H₂) with high conversion rates (84.7 mmol g^-1 h^-1 for CO and 248.1 mmol g^-1 h^-1 for H₂). Importantly, the syngas composition can be precisely tuned by varying the QD-to-Au NC ratio, offering potential integration with the Fischer-Tropsch process for the production of liquid fuels.