Current state-of-the-art thermal technologies for CO2 capture and concentration (CCC) from industrial emissions and air are energetically inefficient. In contrast, electrochemical CCC (eCCC) using redox carriers can theoretically approach 100% efficiency. However, there are currently few oxygen-stable redox carriers suitable for eCCC. Quinone derivatives have previously been studied as redox carriers as they have no affinity for CO2 in the fully oxidized state and an enhanced affinity for CO2 in their reduced states. Unfortunately, the quinones used in prior studies displayed an unfavorable tradeoff between their second reduction potential (E1/2) and CO2 binding constant (KCO2). As a result, reduced quinones that exhibit a sufficient KCO2 for flue gas or atmospheric CO2 capture have E1/2 values negative of the O2/O2•- reduction potential. To improve our understanding of the structural and electronic relationships that correlate KCO2 and E1/2, we report the largest set of quinones that have been experimentally evaluated for their KCO2 and E1/2 properties. The trends in the E1/2 and KCO2 properties were further investigated through extensive quantum chemical calculations to inform experimental carrier design. Notably, we identified structural handles to manipulate E1/2 and KCO2 properties of quinones; however, the altered steric and electronic effects did not disrupt their linear dependence.
