Ternary Deep Eutectic Solvents Tasked for Carbon Dioxide Capture

TLDR

The study investigates task‑specific ternary deep eutectic solvent systems composed of choline chloride, glycerol, and one of three superbases for their ability to capture and release CO₂ on demand. The authors evaluated these DES systems by measuring CO₂ capture capacity and release performance. The best‑performing DES captured ~10 % CO₂ by weight, with DBN providing the highest capacity, release ease, and low cost, yet only a fraction of theoretical capacity was utilized, and non‑Newtonian viscosities suggest that Stokes–Einstein–Debye relations may not predict performance.

Abstract

Task-specific ternary deep eutectic solvent (DES) systems comprising choline chloride, glycerol, and one of three different superbases were investigated for their ability to capture and release carbon dioxide on demand. The highest-performing systems were found to capture CO2 at a capacity of ∼10% by weight, equivalent to 2.3–2.4 mmol of CO2 captured per gram of DES sorbent. Of the superbases studied, 1,5-diazabicyclo[4.3.0]-non-5-ene (DBN) gave the best overall performance in terms of CO2 capture capacity, facility of release, and low sorbent cost. Interestingly, we found that only a fraction of the theoretical CO2 capture potential of the system was utilized, offering potential pathways forward for further design and optimization of superbase-derived DES systems for further improved reversible CO2 sequestration. Finally, the shear rate-dependent viscosities indicate non-Newtonian behavior which, when coupled to the competitive CO2 capture performance of these task-specific DESs despite a 1 to 2 orders of magnitude higher viscosity, suggest that the Stokes–Einstein–Debye relation may not be a valid predictor of performance for these structurally and dynamically complex fluids.