Boosting Electrochemical CO₂ Reduction on Copper-Based Metal-Organic Frameworks via Valence and Coordination...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Copper-based metal-organic frameworks (MOFs) show promise for electrocatalytic CO2 reduction.
• Existing Cu-based MOFs often exhibit low selectivity and instability for converting CO2 to valuable chemicals.
• Optimizing the metal node's valence and coordination environment is crucial for improving catalytic performance.

Purpose of the Study:

• To develop a Cu-based MOF with enhanced selectivity and stability for electrocatalytic CO2 reduction to ethylene.
• To investigate the effect of copper valence state and coordination environment on CO2 electroreduction pathways.
• To establish a design strategy for highly selective electrocatalytic CO2 reduction catalysts.

Main Methods:

• A novel "reduction-cleavage-recrystallization" method was employed to synthesize Cu(I)-BTC MOFs from Cu(II)-BTC.
• The synthesized Cu(I)-BTC MOFs were characterized to analyze their structure and composition.
• Electrocatalytic CO2 reduction was performed using the modified MOFs, and ethylene selectivity and Faraday efficiency were measured.

Main Results:

• The Cu(I)-BTC MOF exhibited significantly higher catalytic activity and ethylene selectivity (approximately 2.2-fold) compared to Cu(II)-BTC.
• Increasing the concentration of free carboxyl groups in the secondary coordination environment further improved ethylene selectivity.
• The optimized catalyst achieved a high ethylene Faraday efficiency of up to 57% and demonstrated excellent durability for 38 hours.

Conclusions:

• The valence state and coordination environment of copper nodes in MOFs strongly influence CO2 electroreduction performance.
• The synergistic effect between the Cu(I)-O coordination and free carboxyl groups promotes ethylene production by enhancing CO intermediate dimerization and suppressing hydrogenation.
• This study provides a viable platform for designing advanced MOF catalysts for selective electrocatalytic CO2 conversion.