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 <i>c</i>-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 <i>c</i>-COFs, displaying the great potential of 2D <i>c</i>-COFs in electrocatalysis.