Fatty acid‐based deep eutectic solvents for efficient absorption of VOCs : Hydrophobicity and molecular mechanism study

The absorption performance of fatty acid‐based deep eutectic solvents (DESs) for volatile organic compounds (VOCs) of varying hydrophobicity was investigated through a combination of experiments and molecular simulations. Partition coefficient experiments demonstrated the DES composed of tetrabutylammonium bromide (TBAB) and octanoic acid (OCA) in a molar ratio of 1:2 exhibits dual‐functional absorption performance, effectively absorbing both weakly hydrophobic VOCs (e.g., dichloromethane and chloroform) and strongly hydrophobic VOCs (e.g., limonene and octamethylcyclotetrasiloxane). Fatty acid‐based DESs retained both absorption performance and structural stability in five absorption–desorption cycles. Both VOC and solvent hydrophobicity are likely to positively affect absorption performance, with higher hydrophobicity leading to stronger absorption ability. Molecular simulations uncover that VOC absorption in TBAB:OCA can be attributed to three mechanisms: (1) large free volume of TBAB:OCA, (2) electrostatic interactions between TBAB and weakly hydrophobic VOCs that promote solubilization, and (3) Van der Waals interactions between OCA and strongly hydrophobic VOC that enhance absorption.