Ternary Deep Eutectic Solvents Tasked for Carbon Dioxide Capture

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 similar to 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.