Since the first ionic liquid was prepared in 1914, ionic liquids have not only increased in quantity, but also expanded in variety. Ionic liquids are salts composed of organic cations and inorganic or organic anions that are liquid at or near room temperature, often called room temperature ionic liquids, or room temperature molten salts. When the organic cation is morpholinium, the ionic liquid is called morpholinium salt ionic liquid. Morpholinium salt ionic liquid with ideal characteristics, has been actively studied at home and abroad in recent years, and it has become a kind of alternative energy material attracting much attention. Figure 1 shows the general structure of morpholinium salt ionic liquids. Furthermore, morpholinium salt ionic liquid is characterized by its designability in structure. Morpholinium salt ionic liquid can be designed as functional ionic liquid containing various groups, so that it not only has the properties of ordinary ionic liquid, but also contains special groups to make the ionic liquid has special properties.
Figure 1. Structure of morpholinium salt ionic liquids.
When the substituents are different, the synthesis process of morpholinium salt ionic liquid will be different. For example, several kinds of morpholinium salt ionic liquids have been synthesized by a research team at room temperature, introducing allyl functional groups into the structures. In addition, a team synthesized a morpholinium salt ionic liquid by the reaction of n-methyl morpholine, n-ethyl morpholine and different substituent groups. In this method, the raw material is dissolved and heated, and the reaction at room temperature is reduced from two days to two hours. At the same time, the yield is increased from 58% to 85%, and a very pure product can be obtained without too much operation.
Figure 2. Experimental procedure used to prepare TiO2.