Hydrophobic deep eutectic solvents: Current progress and future directions

[Display omitted] Deep eutectic solvents (DESs) are novel ‘green’ solvents that have recently gained considerable interest from the scientific community in different sectors. They are considered biocompatible, chemically stable, biodegradable, low volatile, and also non-flammable. The physicochemical properties of DESs are highly tunable and can be customized to meet the needs of a particular mission. A new category of DESs, referred to as hydrophobic DESs (HDESs), is considered to be a promising subclass of traditional DESs to resolve the issue of instability their contact with water. The HDESs have been extensively studied for the isolation and extraction of volatile fatty acids, heavy metals, and bioactive compounds from aqueous solutions. However, the HDESs remain briefly addressed in the literature. This review report therefore summarizes the ground-breaking and innovative efforts of the HDESs, including their properties and applications, which have so far been lacking in scientific literature. In addition, the prospects of HDES application in medicine (e.g., control of COVID-19 pandemic) are also highlighted. To end, remarks and possible perspectives are highlighted and concluded in detail.