Enhancing Electrochemical CO2 Reduction via Redox Non-Innocent Spheres in Copper-Coordinated Covalent Organic Frameworks

Abstract

Significant efforts have been dedicated to the development of highly efficient electrocatalysts for electrochemical CO₂ reduction reactions (eCO₂RR). The outer coordination spheres of catalytic centers may play a pivotal role in the reaction pathway and kinetics for eCO₂RR. Herein, three single copper sites coordinated Aza-fused conjugated organic frameworks (Aza-COFs-Cu) with different outer coordination spheres around Cu sites are designed. Experiment and density functional theory (DFT) calculation results reveal that the redox non-innocent outer spheres around Cu sites significantly influence the catalytic performance of Aza-COFs-Cu for eCO₂RR. When adjacent redox non-innocent groups of uncoordinated aromatic-N and quinone around the Cu centers act as the symmetry-breaking sites, the energy-consuming activation process of CO₂ molecules can be accelerated via the H⁺/e^- transfer process to form *COOH intermediates, which will significantly improve the performance for eCO₂RR. This study provides a new perspective on the design of more advanced electrocatalysts for eCO₂RR through redox non-innocent spheres engineering.

Keywords: covalent organic frameworks; electrochemical CO2 reduction; functional groups; redox non‐innocent sphere; symmetry‐breaking site.