These guidelines are admittedly crude, relying on the assumptions that reaction with CO 2 proceeds through an EEC or EECC mechanism and the half-wave potential of O 2 does not change in the presence of quinone species. Moreover, other factors including but not limited to CO 2 concentration, temperature, electrolyte concentrations and solvents are likely to affect the desired properties of the quinones. Incorporation of these factors goes beyond the scope of the present article and these guidelines and therefore await full validation by explicit experiments and calculations in the presence of O 2 . However, the finding of a general trade-off between the redox potential and the strength of CO 2 capture is of value for the design of improved redox active molecules for electrochemical carbon dioxide capture.