Due to their unique properties, ionic liquids have offered great potential for developing clean catalytic technologies. After a short introduction of their advantages in green catalysis, recent advances in ionic liquid catalysis are reviewed with emphasis on four hot fields, viz. biomass conversion in ionic liquids, catalytic production of fine chemicals in ionic liquids, supported ionic liquid phase catalysis, as well as Friedel–Crafts reactions in ionic liquids. In particular, through selected samples, we show here the advantages and potential of ionic liquids in exploring cleaner catalytic technologies, as compared to traditional catalytic processes. Finally, further development of ILs in catalysis is briefly prospected.

★★★★☆ Green Chem., 2011, 13, 2619–2637

A new class of liquid fluorescent organic salts was designed and prepared through via a strategy of ionic liquidization. These new ionic liquid materials exhibited strong green fluorescence and remarkable solvent-dependent photoluminescence under UV irradiation. Their physicochemical properties, especially the fluorescent behaviour, were studied intensively.

★★★☆☆ Zhang QH,Yang BQ,Zhang SG,et al. Ionic Liquidized-naphthalenesulfonamide: Successful Fabrication Of Liquid Fluorescent Materials[J]. J. Mater. Chem.,2011,21:16335-16338.

Six ionic liquid (IL)-modified dyes were synthesized and characterized. Compared to the methyl red and methyl orange, these IL-modified [MR]
- or [MO]
-based dyes exhibit lower melting points and enhanced solubility, and can be used as sensitive indicators towards free proton in both aqueous and non-aqueous solutions. This work also supplies a new concept of developing novel modified materials with the ILs.

★★★☆☆ Analyst, 2011, 136, 1302–1304

Nine 1-allyl-3-alkylimidazolium ([ACnIm]) or 1-vinyl-3-alkylimidazolium ([VCnIm]) dicyanamides (DCA) were prepared and characterized, and their physicochemical properties were studied in detail. Except for [AVIm]DCA and [AC4Im]DCA, the other dicyanamides with hexyl or longer alkyl chains on the cation exhibited the characteristic of hydrophobicity. Among them, [AC8Im]DCA and [AC10Im] DCA were found to possess similar densities to water, i.e. 1.007 g cm
3 and 0.988 g cm
3 at 25 C, respectively. Interestingly, a reversible phase reversion of a [AC8Im]DCA/H2O mixture was observed as the temperature varied. These environmentally-friendly liquid materials have potential applications as precursors for syntheses of conducting polymeric materials.

★★★☆☆ J. Mater. Chem., 2011, 21, 6864–6868

A new series of ionic liquids composed of three cyclic sulfonium cations and four anions has been synthesized and characterized. Their physicochemical properties, including their spectroscopic characteristics, ion cluster behavior, surface properties, phase transitions, thermal stability, density, viscosity, refractive index, tribological properties, ion conductivity, and electrochemical window have been comprehensively studied. Eight of these salts are liquids at room temperature, at which some salts based on [NO3] and [NTf2] ions exhibit organic plastic crystal behaviors, and all the saccharinbased salts display relatively high refractive indices (1.442–1.594). In addition, some ionic liquids with the [NTf2] ion exhibit peculiar spectroscopic characteristics in FTIR and UV/Vis regions, whilst those salts based on the [DCA] ion show lower viscosities (34.2–62.6 mPas at 20℃) and much higher conductivities (7.6–17.6 mScm-1 at 20℃) than most traditional 1,3-di-ACHTUNGTRENUNGalkylimidazolium salts.

Keywords: electrochemistry · ionic liquids · performance · physicochemical properties · sulfonium ions

★★★★☆ Zhang QH,Liu SM,Li ZP,et al. Novel Cyclic Sulfonium-based Ionic Liquids: Synthesis, Characterization, And Physicochemical Properties[J]. Chem. Eur. J.,2009,15:765-778.

A series of ionic liquids (ILs) based on nitrile-functionalized imidazolium, pyridinium, and quaternary ammonium as cations and chlorides and tetrafluoroborate, hexafluorophosphate, dicyanamide, and bis- (trifluoromethanesulfonyl)imide as anions have been prepared and characterized. The physicochemical properties such as spectroscopic, thermal, solubility, surface, electrochemical, tribological, and toxic properties were comparatively studied. The results showed that the incorporation of a CN group to cations could result in remarkable changes in these properties. The reason resulting in such remarkable differences in the properties may be attributed to the conformational changes in the imidazolium groups caused by the interaction between the CN group with other neighboring cations or anions and the enhancement in hydrogen-bonding interactions due to the incorporation of a CN group.

★★★☆☆ Zhang QH,Li ZP,Zhang J,et al. Physicochemical Properties Of Nitrile-functionalized Ionic Liquids[J]. J. Phys. Chem. B,2007,111(11):2864-2872.

The carbonylation of amines with propargylic alcohol using CO2 as carbonyl source to yield N-substituted 4-methylene-2-oxazolidinones could efficiently proceed in ionic liquids, and various 4-methylene oxazolidinones with high yields could be obtained under relatively mild conditions. This result showed that ionic liquid might be an effective catalyst and reaction medium for the activation of CO2, which also offered a new way to the chemical fixation of CO2.

★★★★☆ Q. Zhang et al. / Tetrahedron Letters 46 (2005) 5907–5911.