In-situ preparation of heteropolytungstic acid on TiMCM-41 nanoporous framework for photocatalytic degradation of textile dye methyl orange

Encapsulation of heteropolytungstic acid (HPA) in the TiMCM-41 framework was carried out by an in-situ synthesis method in order to improve the catalytic activity because it would provide an effective environment for increasing the number of active surface sites for molecular interaction. Fourier transform infrared analysis (FT-IR), P-31 NMR analysis, X-ray diffraction (XRD) analysis, adsorption studies, diffused reflectance studies (DRS) and transmission electron microscopy (TEM) studies were employed to characterize the structure and morphology of as synthesized nanoporous materials. The observed P-31 NMR peak at similar to-14.158 ppm indicates unambiguously that the Keggin structure is retained upon in-situ synthesis of HPA in MCM-41 nanochannels. No obvious extra phases of HPA are seen outside the nanoporous structure from TEM image confirming that HPA is formed only in the nanoporous framework and there is no possibility for leaching out HPA from the nanopores. The modified high surface inorganic substrate was chosen as a simple model for the study of reactions involving the much complex commercial products used for the dyeing of textile fibers. Possibilities to enhance the catalyst performance further by using electron acceptors are also discussed. (C) 2009 Elsevier Inc. All rights reserved.