Keggin ions (PW12O403- (PW12), PW6Mo6O403- (PW6Mo6), PMo12O403-(PMo12)) and TiO2 hybrid thin films were prepared using the layer-by-layer (LBL) method. Their photocatalytic activities were investigated using gaseous 2-propanol (IPA) decomposition. All films were transparent in the visible wavelength range. From XPS and UV-vis spectra, it was confirmed that LBL coating was attained using the same thicknesses between Keggin ions and TiO2. For IPA decomposition, PW12 was the most effective for the combination with TiO2. The PMo12 possessed the highest adsorption capability against gaseous IPA, suggesting the effect of pseudo-liquid phase. Visible-light excitation of reduced Keggin ions will play an important role in the entire photocatalytic activity of IPA decomposition. (c) 2010 Elsevier B.V. All rights reserved.