Ligands-regulated ∗CO adsorption on two-dimensional covalent organic framework promotes selective electrochemical CO2 conversion

Abstract

Manipulating the adsorption/desorption of intermediates at active sites offers a promising strategy to direct specific electrocatalytic pathways. In high overpotential regimes, the desorption of ∗CO from active sites is a major limitation in electrochemical CO₂-to-CO conversion, emphasizing the need to control ∗CO adsorption strength. Here, we report a series of well-defined amide-linked covalent organic frameworks (COFs) featuring alternating tetraaminophenylporphyrin and tetracarboxyphenylporphyrin building blocks, with M₁ and M₂ sites (M₁/M₂ = Co, Fe). Electrochemical tests and computational models reveal that the polar ligand framework plays a key role in regulating ∗CO adsorption, a conclusion supported by operando spectroelectrochemical measurements. Theoretical calculations attribute this regulation to the differing ${\mathrm{d}}_{{\mathrm{z}}^2}$ band centers of the transition metals, driven by intra-layer charge transfer from polar amine bonds. This work underscores the importance of polar ligands in optimizing intermediate adsorption and enhancing CO₂ transformation efficiency.