Synthesis of Inorganic Solids Using the Deep Eutectic Solvent (DES) Route

Abstract

The search for sustainable and environmentally friendly approaches to material synthesis has fueled significant interest in using alternative reaction media, such as ionic liquids. Deep eutectic solvents (DESs) are a promising alternative to ionic liquids due to their low cost, environmental friendliness, and versatile physicochemical properties. This article provides a “close‐up” examination of the synthesis of inorganic materials using type III DES as a reaction medium. The type III DES is an eutectic mixture of choline chloride [(CH 3 ) 3 NCH 2 CH 2 OH] + Cl − and an organic compound, where H‐bonding and ionic interactions lead to the considerable depression of the DESs melting points, making them liquid at around room temperature. The article introduces the fundamental concepts of DESs, including DES types, typical DES components, and resulting solvent properties, emphasizing their distinctive ability to dissolve inorganic precursors, metal coordination environments in DES, and variation in thermal stability. Here, we focus on key synthesis strategies via combustion and precipitation routes, the latter includes solution, solvothermal, and microwave‐assisted synthesis or antisolvent addition techniques. The versatility and solvation properties of DES offer exceptional opportunities for the design and fabrication of diverse compounds, ranging from metal nanoparticles to bulk materials with examples among oxide perovskites, spinels, vanadates, and sulfides. Furthermore, the article explores the specific advantages of DES route in facilitating the synthesis of these materials, such as enhanced precursor solubility, control over morphology, growth, and particle size. The aim of this article is to provide researchers with an understanding of the synthesis of inorganic materials using DESs and stimulate further exploration of novel routes toward materials synthesis in a sustainable manner as well as elucidation of reaction mechanism in DES synthesis routes.