Hydrophobic Natural Deep Eutectic Solvents for Sustainable CO2 Capture: Molecular Insights From Multiscale Modeling

Abstract

This research delves into the physicochemical properties and CO₂ capture ability of a hydrophobic natural deep eutectic solvent (HNADES) consisting of piperitone (PIP) and linoleic acid in a 1:1 molar ratio. Through a multiscale computational approach involving COSMO-RS calculations, quantum chemistry methods, and molecular dynamics simulations, we demonstrate that the considered system, via the development of strong hydrogen bonding interactions, both homo- and hetero-associations, and in parallel with nonpolar domains through van der Waals interactions, creates a suitable situation for CO₂ capture. The nonpolar domains provide space available for accommodating CO₂ molecules without interfering with the fluid's hydrogen bonding Gnetwork. Molecular dynamics simulations show that CO₂ molecules are adsorbed following a two-step mechanism: first, adsorption at the gas–liquid interface, and second, subsequent migration into the bulk liquid. Upon exposure to a simulated flue gas, the HNADES is significantly selective toward CO₂, which permeates the fluid, with N₂ and O₂ molecules remaining predominantly, in the gas phase. The desorption of the adsorbed CO₂ is possible after a heating process, thus enabling sorption–desorption cycles for practical use. This sorbent has advantages of being eco-friendly, having zero vapor pressure, and low water solubility, which makes it an optimal candidate for being involved in sustainable carbon capture technologies.