The influence of water molecules on ionic liquid (IL; 1-butyl-3-methylimidazolium tetrafluoroborate) intercalated montmorillonite (M-IL) and the selectivity of IL have been studied. The intercalation behavior of IL into an IL-intercalation compound containing various amounts of water, (M-ILW) was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and a selected area electron diffraction pattern (SAED). The structural change of MIL influenced by the water was also confirmed by a TEM study. Based on the amount of interlayer exchangeable cations as measured by inductively coupled plasma (ICP), the extent of the intercalation and arrangement of cations in the interlayers of M-IL treated by different amounts of water was studied. In addition, the Raman spectroscopy results showed that the water molecules do not interact with both the IL and the montmorillonite. These results suggest that the IL-intercalation compound can maintain its property in water due to its high water resistance. Moreover, this technique would be useful for the adsorption reaction and fabrication of montmorillonite composite materials using non-polar organic molecules. (C) 2014 Elsevier B.V. All rights reserved.