Electrochemical CO₂ Capture by a Quinone-Based Covalent Organic Framework

Electrochemical CO₂ capture is an emerging technology that promises to be more energy-efficient than traditional thermal or pressure-swing processes. Herein, the first evidence of electrochemical capture of CO₂ using a covalent organic framework (COF) is presented. We hypothesized that the assembly of anthraquinone units into a well-defined porous framework electrode would lead to enhanced electrochemical CO₂ capture compared to previous approaches that grafted anthraquinones on carbon supports and suffered from low CO₂ capacities and stabilities. To test this, an anthraquinone-based COF is employed, and it is found that the quinones are electrochemically accessible for reversible CO₂ capture in an ionic liquid electrolyte. The system achieves a high electrochemical CO₂ uptake capacity >2.6 mmol g^-1 COF, reaching half of the theoretical CO₂ capacity of the material and surpassing the capacities of anthraquinone-functionalized carbons. The stability and CO₂ uptake rate issues encountered with the ionic liquid system are also addressed by using aqueous electrolytes where we attained stable carbon capture for 500 cycles with a 99.6% Coulombic efficiency and an electrical energy consumption of 31 kJ mol_CO2^-1. The use of covalent organic framework electrodes can become a general strategy for understanding and enhancing the electrochemical CO₂ capture.