Triazine-Functionalized Covalent Organic Framework Ultrathin Films for Enhancing Local CO₂ Concentrations in...

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical CO2 reduction (CO2R) using transition-metal catalysts shows limited selectivity for high-value products.
• Organic layers can improve CO2R selectivity but often lack structural and mechanical stability.
• Understanding the role of organic layers in modifying catalyst performance is crucial.

Purpose of the Study:

• To design and investigate a stable, well-defined organic layer for enhanced CO2R.
• To elucidate the mechanism by which the organic layer influences catalyst selectivity and stability.
• To improve the selectivity and efficiency of producing value-added products from CO2.

Main Methods:

• Fabrication of ~4 nm-thick covalent organic framework (COF) films with ~3 nm pores on a cm^2 scale.
• Electrochemical characterization of COF-modified Au, Sn, and Cu catalysts.
• Operando electrochemical spectroscopies and density functional theory (DFT) calculations.

Main Results:

• COF films restricted water access and enhanced local CO2 concentration via strong adsorption.
• Improved Faradaic efficiencies were observed for Au, Sn, and Cu catalysts modified with COF.
• Cu catalyst deactivation was suppressed, leading to a 2-fold increase in ethylene selectivity.
• DFT calculations and spectroscopy revealed increased CO coverage and stronger Cu-COF binding, promoting key ethylene intermediates.

Conclusions:

• Well-defined COF films serve as effective organic layers for enhancing CO2R.
• The COF layer's structure and chemical properties improve selectivity and catalyst stability.
• This work provides a pathway for designing advanced catalysts for efficient CO2 conversion.