Microstructure and Microenvironment Regulation of Covalent Organic Frameworks for Electrochemical CO₂ Reduction...

The growing energy crisis and environmental concerns have drawn significant attention to the electrochemical CO₂ reduction reaction (eCO₂RR), which can directly convert CO₂ into high-value-added chemicals. Covalent organic frameworks (COFs) featured with their distinctive pore structures and chemical tunability have demonstrated promise for CO₂ conversion. The current research mainly focuses on the macroscopic regulation of COFs, exploring their applications in eCO₂RR through synthesis methods, conductivity optimization, structural modification, etc. However, the critical role of the microstructure and microenvironment in modulating catalytic performance remains unexplored. This review comprehensively summarizes the recent advances in optimizing the eCO₂RR performance of COF-based materials via the microstructure and microenvironment engineering at the active sites, including precise control of charge distribution and adsorbed species concentration. Various strategies such as ligand engineering, linkage engineering, and substituent effect have been introduced to tune the local electron density and improve their charge distribution, thereby enhancing the catalytic activity. Furthermore, how selective adsorption of specific anions and cations on the active site alters the adsorption energy of key intermediates is highlighted, steering the reaction pathway. Finally, the current challenges in COFs for eCO₂RR are outlined and potential solutions providing valuable insights for the rational design of next-generation COF electrocatalysts are proposed.