Integrating Enrichment, Reduction, and Oxidation Sites in One System for Artificial Photosynthetic Diluted CO₂ Reduction

Abstract Artificial photosynthetic diluted CO₂ reduction directly driven by natural sunlight is a challenging, but promising way to realize carbon‐resources recycling utilization. Herein, a three‐in‐one photocatalytic system of CO₂ enrichment, CO₂ reduction and H₂O oxidation sites is designed for diluted CO₂ reduction. A Zn‐Salen‐based covalent organic framework (Zn‐S‐COF) with oxidation and reductive sites is synthesized; then, ionic liquids (ILs) are loaded into the pores. As a result, [Emim]BF₄@Zn‐S‐COF shows a visible‐light‐driven CO₂‐to‐CO conversion rate of 105.88 µmol g⁻¹ h⁻¹ under diluted CO₂ (15%) atmosphere, even superior than most photocatalysts in high concentrations CO₂. Moreover, natural sunlight driven diluted CO₂ reduction rate also reaches 126.51 µmol g⁻¹ in 5 h. Further experiments and theoretical calculations reveal that the triazine ring in the Zn‐S‐COF promotes the activity of H₂O oxidation and CO₂ reduction sites, and the loaded ILs provide an enriched CO₂ atmosphere, realizing the efficient photocatalytic activity in diluted CO₂ reduction.