Carboxylate-functionalized　imidazolium　ionic　liquids　(CFIMILs)　were　synthesized　via　a　one-pot　quaternization　reaction　and　serve　as　draw　solutes　for　the　first　time　for　forward　osmosis　(FO)　desalination.　It　provides　a　solution　to　simultaneously　overcome　the　problems　plaguing　the　use　of　pressure-driven　membrane　technologies　to　extract　water　from　saline　water　–　low　water　recovery　efficiency　and　high　reverse　solute　diffusion.　The　CFIMILs　contain　a　substituted　5-membered　imidazole　ring　and　fully　ionize　into　ionic　species　in　water.　These　characteristics　endow　CFIMILs　with　capability　of　high　water　recovery　efficiency　and　minimal　reverse　diffusion　in　FO.　Sodium　salt　of　1-acetate-2,3-dimethyl　imidazole　ionic　liquid　(IL-1)　at　0.8　M　produces　water　fluxes　of　63.6　LMH　(PRO　mode)　and　29.5　LMH　(FO　mode)　against　the　DI　water　feed,　greatly　outperforming　conventional　NaCl　draw　solute　and　other　synthetic　draw　solutes.　Efficient　water　recovery　is　achieved　using　IL-1　for　seawater　desalination　with　a　water　flux　5　times　higher　than　that　of　NaCl.　Particularly,　CFIMILs　draw　solutes　have　negligible　reverse　diffusion　in　FO　and　are　recycled　completely　via　an　MD　process　with　good　reproducibility　when　reused　to　FO,　demonstrating　great　potentials　of　CFIMILs　as　a　new　class　of　draw　solutes　for　FO　water　treatment.　©　2018