Immobilization of catalytic sites on quantum dots by ligand bridging for photocatalytic CO2 reduction

Harvesting solar energy to convert carbon dioxide (CO2) into fossil fuels shows great promise to solve the current global problems of energy crisis and climate change. To achieve this goal, it is desirable to develop efficient catalysts with visible light response to cater for the solar spectrum. CdTe QDs are ideal candidates for absorbing visible light, but it is difficult to directly perform CO2 reduction due to the lack of effective catalytic sites. Herein, we report a strategy for the activation of mercaptopropionic acid (MPA)-capped CdTe QDs for visible-light-driven CO2 reduction, in which iron ions (Fe2+) are immobilized onto CdTe QDs using L-cysteine as a bridging ligand (CdTe-b-Fe). This ligand bridging strategy can immobilize Fe2+ ions on the surface of CdTe QDs as catalytic sites, and these catalytic sites can be conveniently adjusted by directly adding different types or numbers of metal ions. In addition to effectively immobilizing catalytic sites, the bridging ligands can also provide a pathway for electron transport between CdTe QDs and the catalytic sites. The CdTe-b-Fe QD system based on the ligand bridging strategy exhibits excellent catalytic properties: the yield of CH4/CO (two products together) is 126 μmol g−1 h−1, and the selectivity for carbon-based products approaches 98%. This work presents a facile strategy for immobilizing catalytic sites on QDs and provides a platform for designing efficient visible-light driven catalysts for CO2 reduction.