CoN Sites Constructed by Anchoring Co Porphyrins on Vinylene-Linked Covalent Organic Frameworks for Electroreduction of Carbon Dioxide.

Developing effective electrocatalysts for CO reduction (CO RR) is of critical importance for producing carbon-neutral fuels. Covalent organic frameworks (COFs) are an ideal platform for constructing catalysts toward CO RR, because of their controllable skeletons and ordered pores. However, most of these COFs are synthesized from Co-porphyrins or phthalocyanines-based monomers, and the available building units and resulting catalytic centers in COFs are still limited. Herein, Co-N sites are first developed through anchoring Co porphyrins on an olefin-linked COF, where the Co active sites are uniformly distributed in the hexagonal networks. The strong electronic coupling between Co porphyrins and COF is disclosed by various characterizations such as X-ray absorption spectroscopy (XAS) and density functional theory calculation (DFT). Thanks to the CoN sites, the catalytic COF shows remarkable catalytic activity with Faraday efficiencies (FE ) of 84.2-94.3% at applied potentials between -0.50 and -0.80 V (vs RHE), and achieves a turnover frequency of 4578 h at -1.0 V. Moreover, the theoretical calculation further reveals that the CoN sites enable a decrease in the overpotential for the formation COOH*. This work provides a design strategy to employ COFs as scaffold for fabricating efficient CO electrocatalysts.