Altering electronic states of Cu sites in Covalent organic frameworks for synthesis of formate via CO2 reduction

Covalent organic frameworks (COFs) have been well developed to construct electrocatalysts for CO2 reduction (CO2RR) towards CO. However, how to synthesize liquid products is still a challenge due to the lack of suitable catalytic centers. Herein, we have first achieved catalytic COF for highly efficient formate synthesis via CO2RR by modulating the electronic states of CuN4 sites. The flowed electrons from electron-rich dithiophene linker to the Cu2+ promoted the electron transferring along the frameworks, contributed to high electronic conductivity and reductive ability. The designed catalyst showed higher activity with a turnover of frequency value of 486.2 h- 1, and selectivity with faradic efficiencies for HCOOH of 84%. The theoretical calculation and the in-situ synchrotron radiation Fourier transform infrared (SR-FTIR) spectroscopy measurements revealed that dithiophene made catalytic centers easily formed the intermediate OCOH* and suppressing the competing intermediate H*, thus enhancing the activity and selectivity in the carbon dioxide reduction.