This state-of-the-art review examines the synergistic effects and applications of binary mixtures of ionic liquids (ILs), delineating their potential as versatile solvents in various fields. Binary mixtures of ILs have gathered compelling attention due to their uncommon properties and interactions, offering tailored solutions for various scientific and industrial applications [1].

The review surveys the synthesis and characterization of binary mixtures of ILs, featuring the diverse combinations of anions and cations employed to obtain desired properties. The physicochemical properties of binary mixtures, including conductivity, viscosity, thermal stability, phase behaviour and solvation behaviour, are examined to expound the synergistic effects of mixing different ILs [2]. In addition, the review analyses the thermodynamic aspects of binary mixtures, investigating miscibility, phase transitions, and phase diagrams to comprehend their complex behaviour under changing conditions.

A detailed analysis of the applications of binary mixtures of ILs reveals their versatility in extraction, separation processes, catalysis, green chemistry, and energy storage. In catalysis, binary mixtures of ILs show enhanced selectivity, catalytic activity, and recyclability compared to individual ILs, effectively synthesizing fine chemicals and organic compounds [3]. In separation and extraction processes, binary mixtures of ILs exhibit better performance in the selective recovery of industrial effluents, electronic waste, and metals from ores, contributing to environmental protection and sustainable resource management.

Moreover, binary mixtures of ILs have exhibited promising uses in energy storage, serving as electrolytes in supercapacitor systems and advanced batteries. Their thermal stability, high ionic conductivity, and wide electrochemical stability window make them excellent candidates for enhancing the safety and performance of energy storage devices, promising the development of next-generation energy technologies [4].

The review also discusses the role of binary mixtures of ILs in fostering green chemistry practices by replacing perilous organic solvents in various chemical processes. Their nontoxicity, low volatility, and recyclability help reduce environmental pollution and minimize waste generation, coinciding with sustainable chemistry and technology principles.

Finally, the review pinpoints future research directions and issues in the field of binary mixtures of ILs, highlighting the need for further investigation of their fundamental characteristics, improvement for specific uses, and incorporation in industrial processes [5-6]. In conclusion, this state-of-the-art review provides valuable perceptivity concerning the synergistic effects and applications of binary mixtures of ILs, emphasizing their immense potential as sustainable solvents for diverse scientific and industrial endeavours.