Cationic Microenvironment Enhancing Covalent Organic Frameworks for Electrocatalytic CO₂ to CH₄ Conversion

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrocatalytic reduction of carbon dioxide (CO2) to methane (CH4) is challenging due to slow kinetics and competing reactions.
• Existing methods often struggle with selectivity and efficiency in deep CO2 reduction.

Purpose of the Study:

• To develop a novel strategy for enhancing CO2 electroreduction to CH4.
• To investigate the role of a cationic microenvironment in improving catalyst performance.

Main Methods:

• Synthesis of a tetra-alkylammonium cation-functionalized copper porphyrin covalent organic framework (Cu-Tph-COF-N+).
• Electrocatalytic reduction of CO2 to CH4 at -1.2 V versus RHE.
• Mechanistic studies using theoretical calculations and in situ spectroscopy.

Main Results:

• Cu-Tph-COF-N+ achieved a CH4 Faradaic efficiency of 66.8%, outperforming its hydroxyl-functionalized analogue.
• The cationic framework concentrated CO2, regulated proton transfer, and stabilized key intermediates (*COOH, *CHO).
• Enhanced turnover frequency and partial current density were observed.

Conclusions:

• Cationic microenvironment engineering is an effective strategy for steering CO2 electroreduction towards deep reduction products like CH4.
• This approach offers a general method to improve selectivity and efficiency in multi-step electrocatalytic processes.