Covalent Organic Framework Stabilized Single CoN ₄ Cl ₂ Site Boosts Photocatalytic CO ₂ Reduction into Tunable Syngas

Abstract Solar carbon dioxide (CO 2 ) reduction provides an attractive alternative to producing sustainable chemicals and fuel. However, the construction of a highly active photocatalyst was challenging because of the rapid charge recombination and sluggish surface CO 2 reduction. Herein, a unique Co−N 4 Cl 2 single site was fabricated by loading Co species into the 2,2′‐bipyridine and triazine‐containing covalent organic framework (COF) for CO 2 conversion into syngas under visible light irradiation. The resulting champion catalyst TPy‐COF‐Co enabled a record‐high CO production rate of 426 mmol g −1 h −1 , associated with the unprecedented turnover number (TON) and turnover frequency (TOF) of 2095 and 1607 h −1 , respectively. The catalyst also exhibited favorable recycling performance and widely adjustable syngas production (CO/H 2 ratio: 1.8 : 1–1 : 16). A systematical investigation including operando synchrotron X‐ray absorption fine structure (XAFS) spectroscopy, in situ attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS), and theoretical calculation indicated that the triazine‐based COF framework promoted the charge transfer towards the single Co−N 4 Cl 2 sites that greatly promoted the CO 2 activation by lowering the energy barrier of *COOH generation, facilitating the CO 2 transformation. This work highlights the great potential of the molecular regulation of COF‐derived single‐atom catalysts to boost CO 2 photoreduction efficiency.

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