Overall, we have demonstrated that the trade-off between redox potential and strength of electrochemical CO 2 capture is general to the fine-tuning of quinones by functional group substitutions through (i) different numbers of substituents and (ii) different types of substituents. We have also demonstrated that different trade-offs exist for different types of quinones (AQ vs. BQ) and the trade-offs are general to both the EEC and EECC mechanisms. This raises questions about whether functional group substitutions can be used to address oxygen sensitivity issues in these systems, while maintaining sufficient CO 2 reactivity.