In this article, we have investigated the effect of functional group substitution on the thermodynamics of electrochemical CO 2 capture by quinones. Using the EEC and EECC schemes to describe the overall capture process, we have identified the electron density of the oxyanion Q 2-species as the key factor governing the thermody-namics of the electrochemical reduction and carbon capture steps. After benchmarking DFT calculation of the electrode potentials to experimental values, we quantified the thermodynamic driving force of the electrochemical reduction and carbon capture steps.