Oxygen-tolerant CO<sub>2</sub> electroreduction over covalent organic frameworks via photoswitching control oxygen passivation strategy.

Zhu, Hong-Jing; Si, Duan-Hui; Guo, Hui; Chen, Ziao; Cao, Rong; Huang, Yuan-Biao · Nat Commun · 2024

basic_science · Level V

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Abstract

The direct use of flue gas for the electrochemical CO<sub>2</sub> 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 CO<sub>2</sub> electrocatalysis under aerobic environment. The DAE moiety in the material can reversibly modulate the O<sub>2</sub> 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<sup>-2</sup> at -1.0 V vs. reversible hydrogen electrode by co-feeding CO<sub>2</sub> and 5% O<sub>2</sub>. This work presents an oxygen passivation strategy to realize efficient CO<sub>2</sub> electroreduction performance by co-feeding of CO<sub>2</sub> and O<sub>2</sub>, which would inspire to design electrocatalysts for the practical CO<sub>2</sub> source such as flue gas from power plants or air.