Engineering CO₂ Pre-Activation in In-MOF for Enhancing its Electroreduction Activity

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Electrocatalytic CO2 reduction (ECR) efficiency depends on CO2 adsorption and pre-activation.
• Direct structural evidence correlating CO2 pre-activation extent with ECR performance is lacking.

Purpose of the Study:

• To visualize distinct CO2 pre-activation configurations using crystalline model catalysts.
• To unravel the critical role of CO2 pre-activation in ECR performance.
• To establish a correlation between CO2 pre-activation and electroreduction outcomes.

Main Methods:

• Utilized two Indium-based Metal-Organic Frameworks (In-MOFs), FJU-350 and FJU-351, as crystalline model catalysts.
• Employed single-crystal X-ray diffraction to analyze CO2 adsorption configurations.
• Conducted theoretical calculations to confirm charge transfer and energy barrier effects.

Main Results:

• FJU-350 demonstrated superior ECR performance (90.9% FEformate at -1.4 V vs. RHE) compared to FJU-351 (88.6% at -1.6 V).
• FJU-350 stabilized a uniquely bent CO2 species (127.2°) via a polarized carboxyl-oxygen site, indicating pronounced pre-activation.
• FJU-351 accommodated near-linear CO2 (≥153.3°) through delocalized π-interactions, lacking directed pre-activation sites.

Conclusions:

• Distinct structural microenvironments in In-MOFs dictate CO2 pre-activation configurations.
• A highly distorted, bent CO2 configuration significantly facilitates charge transfer and lowers energy barriers for ECR.
• Precise micro-environment engineering of catalysts is a strategic approach for designing efficient electrocatalytic CO2 reduction systems.