Construction of Interlayered Single-Atom Active Sites on Bipyridine-Based 2D Conjugated Covalent-Organic Frameworks for Boosting the C2 Products of Electrochemical CO2 Reduction

The electrochemical carbon dioxide reduction (eCO₂RR) shows great potential in the realization of carbon neutrality, which requires a dedicated catalyst design. To develop electrocatalysts that favor C₂ products, herein, the synthetic protocol for engineering interlayered single-atom metal active sites on the bipyridine-linked 2D conjugated covalent-organic framework (2D c-COF) has been developed by utilizing the interlayer π–π stacking. The resultant M@BTT-BPy-COF (where M = Cu, Ni, and Fe) provides fully exposed single-atom active sites with a suitable interdistance for catalyzing the key C–C coupling in the eCO₂RR process. The Faradaic efficiency of ethanol (FE_ethanol) exceeds 40% with M@BTT-BPy-COF at −0.8 V vs RHE, outperforming most reported COF-based electrocatalysts. Density functional calculations suggest that the proximal active sites in the pore channel of COFs are the key active sites for promoting the C–C coupling to generate ethanol product. This investigation presents a novel way to engineer single-atom catalytic centers on 2D c-COFs, displaying the great potential of 2D c-COFs in electrocatalysis.