Magnetic ionic liquids: synthesis, properties and applications

By combining the tunability and little volatility of ionic liquids with magnetic responsiveness, magnetic ionic liquids (MILs) have become multipurpose materials that provide easy magnetic manipulation, separation, and recovery. With a focus on the connections between molecular structure, magnetic response, viscosity, transport properties, stability, and functional performance, this review critically explores recent developments in the design, synthesis, physicochemical properties, and applications of MILs. For use in catalysis, extraction, separation, environmental remediation, sensing, energy, and smart materials, recent advancements such as metal-ligand engineering, bimetallic MILs, sol-gel immobilization, microwave-assisted synthesis, and magnetic nanoparticle-based hybrids are highlighted. In addition to the frequently disregarded problems of metal leaching, toxicity, recyclability, cost, and scalability, special emphasis is paid to the ongoing trade-off between magnetic susceptibility and viscosity. The review also identifies two new methods for creating task-specific MILs with optimum properties: computational modeling and machine learning-assisted design. Overall, this review shows how MILs have evolved from proof-of-concept magnetic liquids to functioning platforms that are technologically relevant, rationally constructed, recoverable, and sustainable.