Full Quantum-Dots-Based S-Scheme Heterojunctions for Photocatalytic Biomass Aldol Condensation Integrated with CO₂...

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 CO₂, enabling synergistic furfural aldol-condensation with acetone to yield a high-value-added product, integrated with the selective CO₂-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.