Abstract A series of crown ether complex cation ionic liquids (CECILs) were designed, synthesised and characterised by NMR spectroscopy, HRMS, thermogravimetric differential thermal analysis (TG-DTA) and elemental analysis. Their applications in various organic reactions were investigated:[15-C-5Na][OH],[15-C-5Na][OAc],[18-C-6K][OH] and [18-C- 6K][OAc](15-C-5=[15] crown-5; 18-C-6=[18] crown-6) efficiently catalysed the Michael ...