Boosting CO₂ Electroreduction over a Covalent Organic Framework in the Presence of Oxygen

Herein, we propose an oxygen-containing species coordination strategy to boost CO2 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-N2O2 sites, is developed and synthesized for enhancing the CO2RR 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 CO2 molecules and stabilize the key intermediate *COOH of the CO2RR 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 CO2RR. Thus, NiPc-Salen(Co)(2)-COF exhibits high oxygen-tolerant CO2RR performance and achieves outstanding CO Faradaic efficiency (FECO) 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 CO2 feed gas (FECO=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 CO2 atmosphere (j(CO)=104.8 mA cm(-2)). It is worth noting that an excellent FECO 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 CO2RR under O-2 atmosphere by utilizing the *OOH intermediates of ORR to boost CO2 electroreduction.