Photocatalysts with general formula Bi2MNbO7 (M=ln, Al, Fe, Sm) have been prepared following the sol-gel method by gelling niobium ethoxide with bismuth acetate and In, Al, Fe and Sm precursors. XRD, TGA/DTA, FT-IR, UV-vis, SEM and nitrogen adsorption techniques were used to characterize the solids. The evolution of the crystalline phases of the sol-gel samples with the annealing temperature was followed by XRD. At annealing temperatures lower than 400 degrees C crystalline Bi2MNbO7 phases were not detected, while at 800 degrees C only pyrochlore phase was observed. The energy band gap values were found from the UV-vis spectra of the samples calcined at 400 degrees C between 1.43 and 2.24eV. Kinetic t(1/2) (half life) parameters for the photodegradation of methylene blue shown that Bi2FeNbO7 sol-gel catalysts were more active (t(1/2) = 13 min) than TiO2, P-25 (t(1/2) =45 min) reference photocatalyst. For comparative purposes solid state preparations of Bi2MNbO7 were also studied, showing a lower photocatalytic activity than the sol-gel preparations but it was in the same order of TiO2, P-25 catalyst. (c) 2005 Elsevier B.V. All rights reserved.