Boosting CO 2 Electroreduction over a Covalent Organic Framework in the Presence of Oxygen

• Published in: Angewandte Chemie 2024-04, Vol.136 (14)
• Main Authors: Guo, Hui, Si, Duan‐Hui, Zhu, Hong‐Jing, Chen, Zi‐Ao, Cao, Rong, Huang, Yuan‐Biao
• Format: Article
• Language: English
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202319472

Herein, we propose an oxygen‐containing species coordination strategy to boost CO 2 electroreduction in the presence of O 2 . A two‐dimensional (2D) conjugated metal‐covalent organic framework (MCOF), denoted as NiPc‐Salen(Co) 2 ‐COF that is composed of the Ni‐phthalocyanine (NiPc) unit with well‐defined Ni−N 4 −O sites and the salen(Co) 2 moiety with binuclear Co−N 2 O 2 sites, is developed and synthesized for enhancing the CO 2 RR under aerobic condition. In the presence of O 2 , one of the Co sites in the NiPc‐Salen(Co) 2 ‐COF that coordinated with the intermediate of *OOH from ORR could decrease the energy barrier of the activation of CO 2 molecules and stabilize the key intermediate *COOH of the CO 2 RR over the adjacent Co center. Besides, the oxygen species axially coordinated Ni−N 4 −O sites can favor in reducing the energy barrier of the intermediate *COOH formation for the CO 2 RR. Thus, NiPc‐Salen(Co) 2 ‐COF exhibits high oxygen‐tolerant CO 2 RR performance and achieves outstanding CO Faradaic efficiency (FE CO ) of 97.2 % at −1.0 V vs. the reversible hydrogen electrode (RHE) and a high CO partial current density of 40.3 mA cm −2 at −1.1 V in the presence of 0.5 % O 2 , which is superior to that in pure CO 2 feed gas (FE CO =94.8 %, j CO =19.9 mA cm −2 ). Notably, the NiPc‐Salen(Co) 2 ‐COF achieves an industrial‐level current density of 128.3 mA cm −2 in the flow‐cell reactor with 0.5 % O 2 at −0.8 V, which is higher than that in pure CO 2 atmosphere ( j CO =104.8 mA cm −2 ). It is worth noting that an excellent FE CO of 86.8 % is still achieved in the presence of 5 % O 2 at −1.0 V. This work provides an effective strategy to enable the CO 2 RR under O 2 atmosphere by utilizing the *OOH intermediates of ORR to boost CO 2 electroreduction.