As CO2 concentrations have reached record levels, up to 415ppm in 2022, methods of CO2 removal are needed to actively reduce high levels of CO2 and address the effects of anthropogenic climate change. One method that provides a solution is direct air capture (DAC), or the capture of CO2 directly from the atmosphere. Materials such as ionic liquids (ILs), salts that are liquid at room temperature, have been previously investigated for CO2 capture due to their higher thermal stabilities and negligible volatilities when compared to organic solvents. More specifically CO2 reactive ILs (rILs), have been shown to absorb CO2 more selectively at low partial pressures of CO2. By mixing ILs with hydrogen bond donors such as ethylene glycol (EG), deep eutectic solvents (DESs) are formed. DESs are liquid mixtures with a significantly lower melting point than their parent compounds. DESs with ethylene glycol also have improved mass transport due to their reduced viscosity compared to the parent IL, thus increasing CO2 diffusivity. Encapsulation methods, such as formation by Pickering emulsion, have been shown to greatly increase gas-liquid interfacial surface area for ILs and DESs, and improve CO2 uptake rate. An alternative method for increasing the gas-contacting surface area of high viscosity liquid CO2 sorbents is the formation of solvent impregnated polymers (SIPs). SIPs are formed by evenly distributing micro-droplets of liquid within a bulk CO2 permeable polymer via high shear emulsification. The bulk mass is then ground up to create packable hybrid materials. In this study, we demonstrate the fabrication of SIPs with functionalized DESs to further improve CO2 capture rates under DAC conditions. The CO2 isotherms, breakthrough curves, and thermal stability of the fabricated SIPs are characterized in order to assess their applicability in DAC.

Investigation of deep eutectic solvents in solvent impregnated polymers for direct air capture of CO2

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