Electrocatalysisin CO₂‑BindingOrganic Liquids with an Iron Porphyrin

Direct electrochemical upgrading of CO₂ in capture media is an attractive approach to carbon capture that can bypass the energy requirement for the thermal release of pure CO₂. Here we investigate the electrocatalytic activity of iron(tetraphenylporphyrin) in the presence of organic solvents that convert into ionic liquids upon exposure to CO₂. Four different solvent systems were tested, all of which capture CO₂ in the form of an alkyl carbonate (or carbamate) anion and an acidic ammonium cation. The electrocatalytic selectivity exhibited a strong dependence on the acidity of the capture medium, with the most basic solvent affording a high selectivity for production of CO instead of H₂. Experimental and computational studies support a canonical mechanism in which the catalyst reacts with free CO₂ in solution, as opposed to a reaction with the alkyl carbonate that is present in high concentration. Kinetic analysis indicates that the rate-limiting step is changed from C–O protonolysis in traditional solvents to the binding of CO₂ in the capture media. Quantitative ¹³C–¹³C EXSY revealed that the dissociation of the alkyl carbonate into free, solvated CO₂ is very rapid (∼15 s^–1) compared to the interconversion of HCO₃^–/CO₂ in aqueous solution. These results underscore the need to understand the mechanism and kinetics for both the release of captured CO₂ and its electrocatalytic conversion.