Adsorption of phenols (phenol and 2-naphthol) onto the 1,1'-dimethyl-4,4'-bipyridinium (methylviologen :MV2+)-smectite intercalation compounds, which were synthesized by ion exchange reactions, led to the change in the color and the basal spacing. The color change was ascribed to the formation of charge-transfer complex of MV2+ and phenols. The increase in the basal spacing by the reaction with phenols indicates a change in the interlayer microstructure.