Impacts of Quinone Structure on Trade-Offs Between Redox Potential and CO₂ Binding Strength

Quinones are well-studied and promising candidates for redox-active sorbents in electrochemical CO₂ capture and storage (ECCS). Unfortunately, reactivity with O₂ is a persisting issue in the use of quinones. While attempts have been made to tune the redox-potentials of quinones to avoid this, quinones which are more tolerant to the presence of O₂, are also generally less reactive toward CO₂, that is, there is an inherent trade-off. Building off of prior work on anthraquinones and fluorinated benzoquinones [Bui et al., J.Phys.Chem.C., 126, 14 163-14 172,2022], this article investigates how the trade-off varies for a wider range of quinone types. No single unifying trade-off is found; instead distinct quinone families follow distinct trade-offs. A Hückel model is utilized to demonstrate how the change in aromaticity upon two-electron reduction strongly influences the redox-potential, and that given the same change in aromaticity, ortho-quinones will possess a significantly more positive redox potential than non-ortho-quinones. By varying carbonyl placement in otherwise unfunctionalized quinones, the redox-potential may be tuned by a range of up to 0.8 V. One previously uninvestigated quinone for ECCS, 2,3-naphthoquinone, is identified as particularly promising, and nuclear magnetic resonance (NMR) spectroscopy shows its dianion capable of capturing CO₂ but lacks electrochemical reversibility.