Integration of Redox‐Active Viologen Moiety into Bifunctional Covalent Organic Framework for Boosting Electrochemical CO ₂ Overall Reaction

Abstract

Abstract The electrochemical overall CO 2 reduction involving concurrent CO 2 reduction reaction (CO 2 RR) and oxygen evolution reaction (OER) could realize energy conversion but still remains a grand challenge. Herein, a bifunctional cationic covalent organic framework (Vg‐Por(Co)‐COF) is constructed by the redox‐active viologen unit and cobalt porphyrin building block to enhance the electrochemical CO 2 overall reaction. The redox‐active viologen moiety can switch from its original dicationic state to a neutral state, which could facilitate in transfer electron to the active center and enhance the cathodic CO 2 RR. While the anodic OER process, the viologen group can maintain its electron‐deficient oxidation state, and induces the cobalt active center to a trivalent state, which is conducive to the occurrence of the OER. When Vg‐Por(Co)‐COF is employed as both cathodic and anodic catalysts, high CO Faradic efficiencies over 90% are achieved at 2.6 to 3.3 V. The Vg‐Por(Co)‐COF || Vg‐Por(Co)‐COF system achieves a current density of 9.76 mA cm −2 at 3.2 V, outperforming both the Vg‐Por(Co)‐COF || Pt and the neutral COF electrocatalyst COF‐366‐Co || COF‐366‐Co systems under the same conditions. This work opens up a new avenue for exploring bifunctional materials toward efficient electrochemical CO 2 overall reaction.