Covalent organic frameworks (COFs), possessing ordered pores and high-precision functionalization, are regarded as an ideal class of templates to construct catalysts for electrocatalytic carbon dioxide reduction reaction (CO₂RR). 

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

A research team led by Prof. ZENG Gaofeng and Assoc. Prof. XU Qing from the Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences has proposed a multilevel post-synthetic modification strategy to construct catalytic COFs towards CO₂RR with high activity and selectivity.  

The results were published in Nature Communications on June 26.

Catalytic COFs synthesized by the post modification showed a maximum turnover frequency value of 9922.68 h^–1 at –1.0 V and the highest faradaic efficiency of 97.32% at –0.8 V, which were higher than that of the base COF and the single-modified COFs.

Electrocatalysis tests and characterizations revealed that C-N bonds could improve catalytic selectivity and ionic skeleton contributed to higher activity.

Furthermore, theoretical calculations illustrated that the easier formation of immediate *CO from COOH* was the rate-determined step, and methyl groups strengthened electron density.

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