The imidazolium-based ionic liquids (ILs) (1-n-alkyl-3-methylimidazolium tetrafluoroborate, where n = 4, 6-8, 12) were synthesized and characterized in terms of their spectral characteristics, thermal stability, and water, ethanol and cyclohexane vapour sorption behaviour. It was found that the highest hydrophilic character had IL with the shortest alkyl chain on the cation. At the same time, the IL thermal stability was decreased with the increase of the cation alkyl chain length. D'Arcy and Watt and NRTL sorption models allowed to well describe the vapour sorption experimental data. The supported ionic liquid membranes (SILMs) were prepared by impregnation of the porous poly(vinylidene fluoride) (PVDF) membrane with the synthesized ILs. The sorption capacity of PVDF was found to increase after its swelling in IL. An experimental evaluation of the SILMs permeability was carried out for water, ethanol and cyclohexane. The effect of operation parameters such as temperature and concentration of the permeant was studied. It was observed that the presence of the IL strongly influenced the permeability performance of the membrane by reducing the pore sizes and changing the hydrophobic/hydrophilic balance. It is found from the permeation kinetics curves that the SILMs have high potential for separation of organic solvent/water mixtures.