Covalently Supported Phenazine for Electrochemical Capture of Low Concentration CO₂

Electrochemical CO₂ capture (eCC) excels in selectivity, reversibility, low-temperature operation, and reusability, yet liquid-phase systems struggle with mass transfer limitations. In this study, a phenazine-based capture agent was chemically grafted onto carboxylated carbon nanotubes, achieving an active loading of 4.4 wt %. Through stable chemical bonding and a reversible redox reaction, the immobilized phenazine efficiently captures CO₂ at concentrations of ca. 0.1% in a gas-phase flow device. This system exhibits a high CO₂ capture capacity of 4.8 mmol g^-1, achieving nearly 100% release and capture efficiency. It offers a viable pathway for flue gas or air capture and utilization.