Ionic liquids are mostly composed of alkylpyridine or bis-alkylimidazole quaternary ammonium salt cations, chloroaluminate, fluoroborate, hexafluorophosphate and other large anions. It has the advantages of good solubility for certain inorganic and organic substances, wide liquid temperature and electrochemical window range, high thermal stability, and easy preparation. Ionic liquids not only have many excellent physical and chemical properties, but also their properties can be adjusted by changing the structure of anions, cations and substituents, which can be adapted to different application requirements. Morpholinium-based ionic liquids are generally synthesized by the reaction of N-methylmorpholine, N-ethylmorpholine and different substituent groups. Utilizing the designability of the ionic liquid, a functionalized morpholinium-based ionic liquid that satisfies a variety of physical and chemical properties such as liquid range, polarity, acidity, chirality, coordination ability, solubility, etc. can be obtained. Morpholine ionic liquid, as a green medium with ideal characteristics, can be widely used in many fields such as catalysis, chemical separation and extraction, functional materials and interface chemistry.
Figure 1. The structure of morpholinium-based ionic liquids
Applications:
- Applied in organic synthesis: Ionic liquids have special properties and functions by adjusting the structure of anions and cations. Choosing suitable ionic liquids as reaction media or catalysts has been widely used in organic synthesis research. As a reaction medium, the product obtained by reaction in an ionic liquid has high yield and good selectivity. As a catalyst, ionic liquids can accelerate the rate of many reactions. The acidic morpholinium-based ionic liquid can well catalyze the esterification reaction and obtain a higher yield.
- Used in the preparation of nanomaterials: Various organic solvents or templates are often used in the preparation of nanomaterials. The morpholine ionic liquid can be used to prepare nanoparticles. By controlling the structure of the cation of the morpholinium-based ionic liquid, nanoparticles of different sizes can be obtained, thereby forming gold nanoparticles with good dispersion and selectivity. At the same time, the ionic liquid acts as both a reducing agent and a protective reagent, which simplifies the preparation process of nano-ions.
Reference
- Hong-wei Ren, Qing-hong Wang, Shao-hui Guo, Di-shun Zhao, Chun-mao Chen. Comprehensive Insights into the Thermal Stability, Biodegradability, and Combustion Chemistry of Pyrrolidinium-Based Ionic Liquids[J]. European Polymer Journal. 2017, 92, 204–212.
