The C-N bonds can improve the adsorption of CO₂ and ionic skeletons can promote the charge transfer, further enhancing the conductivity. However, directly bottom-up synthesis can hardly realize the co-existence of C-N bonds and ionic frameworks due to the electrostatic repulsion and weak strength of the linkage. 

Motivated by this challenge, a research team led by Prof. ZENG Gaofeng and Associate Prof. XU Qing at the Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences constructed a multilevel post-synthetic modification strategy to construct catalytic COFs towards CO₂RR with high activity and selectivity. The research results were published in Nature Communications.  

The catalytic COFs synthesised by the post modification show a maximum turnover frequencie value of 9922.68 h^–1 at –1.0 V and the highest faradaic efficiencies of 97.32% at –0.8 V, which are higher than that of the base COF and the single-modified COFs. The electrocatalysis tests and characterizations reveal that C-N bonds can improve the catalytic selectivity and ionic skeleton contributes to higher activity. 

Furthermore, the theoretical calculations illustrate that the easier formation of immediate *CO from COOH* is the rate determined step, and methyl groups strengthen the electron density. 

This work provides a deeper understanding of COFs in CO₂ reduction reaction. In the meantime, it sheds light on constructing multilevel post-synthetic modification COFs towards tailored activity and high stability.

Catalytic covalent organic frameworks with bifunctional roles in oxygen reduction reaction (from O₂ to H₂O) and oxygen evolution reaction (from H₂O to O₂) have been first demonstrated by integrating redox-active sites into the Co-porphyrin frameworks. (Image by SARI)