Full Quantum‐Dots‐Based S‐Scheme Heterojunctions for Photocatalytic Biomass Aldol Condensation Integrated with CO ₂ Reduction

Abstract Constructing aggregation‐resistant, full‐Quantum Dot (QD)‐based S‐scheme heterostructures is critical yet challenging for the enhanced photocatalysis. Herein, a charge‐directed and defect‐induced strategy is presented to fabricate a novel full QD‐based heterostructure CdS&CQD and its photocatalytic feature. The CdS&CQD is assembled from a negatively‐charged and sulfur‐vacancy‐rich CdS QD, and a both positively‐charged‐groups and thiophene‐moieties functionalized carbon‐quantum‐dot (CQD). Electrostatic interaction ensures the close contact between CdS and CQD, suppressing the homo‐QD aggregation. Assisted by thiophene groups on CQD and sulfur‐vacancies on CdS, they act as complementary “jigsaw puzzle” motifs, guiding the formation of a chemically bonded Cd–S interface. This process results in a colloidally stable full‐QD‐based CdS&CQD with the maximal active site exposure. The atomic‐level connectivity in CdS&CQD established a robust internal electric field, driving S‐scheme charge transfer with long‐lived excitons and enhanced redox capacity for the photocatalyst. Consequently, CdS&CQD efficiently activates the inert biomass‐derived furfural and CO ₂ , enabling synergistic furfural aldol‐condensation with acetone to yield a high‐value‐added product, integrated with the selective CO ₂ ‐to‐CO reduction. CdS&CQD also displays recycling stability as well as the activity under outdoor sunlight irradiation. This work provides fundamental significance for designing and constructing full‐QDs‐based heterostructures with tailored photocatalytic redox‐capabilities.