Oxygen-tolerant CO₂ electroreduction over covalent organic frameworks via photoswitching control oxygen passivation strategy

The direct use of flue gas for the electrochemical CO₂ reduction reaction is desirable but severely limited by the thermodynamically favorable oxygen reduction reaction. Herein, a photonicswitching unit 1,2-Bis(5’-formyl-2’-methylthien-3’-yl)cyclopentene (DAE) is integrated into a cobalt porphyrin-based covalent organic framework for highly efficient CO₂ electrocatalysis under aerobic environment. The DAE moiety in the material can reversibly modulate the O₂ activation capacity and electronic conductivity by the framework ring-closing/opening reactions under UV/Vis irradiation. The DAE-based covalent organic framework with ring-closing type shows a high CO Faradaic efficiency of 90.5% with CO partial current density of −20.1 mA cm⁻² at −1.0 V vs. reversible hydrogen electrode by co-feeding CO₂ and 5% O₂. This work presents an oxygen passivation strategy to realize efficient CO₂ electroreduction performance by co-feeding of CO₂ and O₂, which would inspire to design electrocatalysts for the practical CO₂ source such as flue gas from power plants or air.