Confining Quantum Dots Within Covalent Organic Framework Cages for Coupled CO₂ Photoreduction and Value-Added Chemical Synthesis.

Abstract

Coupling photocatalytic CO₂ reduction with the synthesis of value-added chemicals represents a promising strategy to mitigate carbon emissions while maximizing solar energy utilization. Quantum dots (QDs) are attractive photocatalysts for such tandem reactions, owing to their size-tunable band structures, abundant surface-active sites, and strong light-harvesting capabilities. However, their implementation is often hindered by severe aggregation and sluggish mass transfer, which limit their photocatalytic performance. Herein, a spatially confined 3D/0D covalent organic framework (COF)/ZnSe QDs step-scheme (S-scheme) heterojunction photocatalyst is reported, prepared via an in situ encapsulation strategy, for concurrent CO₂ photoreduction and organic transformation. The ZnSe QDs are immobilized within the nanoporous cages of the COF, forming a confined microenvironment that suppresses aggregation, enhances photostability, and promotes efficient mass transfer. As a result, the COF/ZnSe heterostructure achieves a CO generation rate of 128.3 µmol g⁻¹ h⁻¹, while synchronously delivering 95.1% conversion of 1-phenylethanol to 1-phenylethanone under light irradiation. The hierarchical COF matrix acts as a nanoreactor, enriching local CO₂ concentration within its porous network, while the rationally designed S-scheme heterojunction facilitates directional charge flow, ensuring robust redox selectivity. This work provides a generalizable strategy for designing advanced heterostructured photocatalysts for efficient bifunctional solar chemical conversions.