Supramolecular deep eutectic solvents and their applications

Abstract

In recent years, the growing awareness of the harmfulness of chemicals to the environment has resulted in the development of green and sustainable technologies. The compromise between economy and environmental requirements is based on the development of new efficient and green solutions. Supramolecular deep eutectic solvents (SUPRADESs), a new deep eutectic solvent (DES) subclass characterized by inclusion properties, are a fresh discovery that could have a significant impact on the development of green chemistry. SUPRADESs known in the literature consist of green ingredients, their physicochemical properties are similar to those of conventional DESs, and their supramolecular nature allows for selective binding of numerous chemical compounds – for many applications SUPRADESs show much higher efficiency compared with DESs. Because of the inclusion of cyclodextrins in their structure, these solvents are able to bind to many compounds through the formation of hydrogen bonds (typical of DESs) and at the same time interact with them in a host–guest mechanism. The combination of the environmentally friendly properties of DESs with those of cyclodextrins could be a breakthrough in the context of green chemistry. This review paper summarizes the available knowledge about SUPRADESs – their composition, physicochemical properties, applications and perspectives. SUPRADESs described in the work are fully green, non-toxic, and biodegradable solvents which are capable of efficiently absorbing many substances. So far, few SUPRADESs are known, but some of them are classified as low melting mixtures (LMM). It is very important to systematize the data available on these green solvents and properly classify them. We hope that identifying their potential and green characteristics will support further promising discoveries.