Immobilization of Keggin and Preyssler tungsten heteropolyacids on various functionalized silica

The Keggin and Preyssler tungsten heteropolyacids, H(3)PW(12)O(40) and H(15)P(5)W(30)O(110), have been immobilized on the inner surface of mesoporous MCM-41, fume silica and silica-gel by means of chemical bonding to aminosilane groups. The materials were characterized by FT-IR spectroscopy, low-angle XRD and BET surface area analysis. The tendencies of heteropolyacids adsorption in solution on functionalized silicas have been investigated by UV-vis. Among the functionalized silica materials, MCM-41 showed the largest amine to silica and the least heteropoly-acid to silica ratios. The BET surface area revealed that in all three cases the surface area decreased after grafting amine group and anchoring of the HPAs clusters. Low-angle XRD analysis showed that by introducing HPA into functionalized MCM-41 the intensity of the main reflection decreased significantly. (c) 2006 Elsevier Inc. All rights reserved.