In Situ Anchoring of Co Single Atoms within Keto-Enamine COFs via the Coordination of an Interlayer N Atom with Co for the Enhanced Photocatalytic CO₂ Reduction Efficiency

Single-atom catalysts (SACs) are prone to agglomeration or migration during catalytic processes, making the development of highly dispersible SACs greatly essential for the performance of photocatalytic CO₂ reduction. Herein, cobalt-containing keto-enamine covalent organic frameworks (COFs) (Co/TpPa-1) are successfully in situ synthesized by utilizing the interlayer nitrogen atom coordinated with metallic cobalt, which is used to effectively prevent the agglomeration of monometallic atoms to ensure the homogeneous dispersion of SACs in the resulting metalized COFs. In the photocatalytic CO₂ reduction, the Co/TpPa-1 composite exhibits significantly enhanced performance compared to the TpPa-1 COFs. The CO yield of 0.05 mM Co/TpPa-1 composite is approximately 414.5 μmol g^-1 h^-1, representing a two-order-of-magnitude improvement over the TpPa-1 COF catalyst (approximately 4.15 μmol g^-1 h^-1). Moreover, the 0.05 mM Co/TpPa-1 composite shows 99.45% selectivity for CO and good stability, maintaining a over 97% CO₂ reduction rate after four cycles. The reason lies in the fact that the interaction between monatomic Co and TpPa-1 COFs enhances visible light absorption and extends the lifetime of the photogenerated carriers by promoting electron transfer through the loaded monatomic Co. This work provides a new idea for the catalyst synthesis with high performance and high selectivity.