Acidic tetra-n-butylammonium (TBA) salts of Keggin type transition-metal-ntonosubstituted polyoxometalate TBA(4)HPW(11)CoO(39) (Co-POM) have been chemically anchored to the amino-modified silica (NH2-(CH2)(x)-SiO2, x = 0, 2, 3) containing 40-710 mu mol NH2-groups per 1 g of support. The interaction of Co-POM with NH2-(CH2)(x)-SiO2 was studied by DR-UV-vis spectroscopy. Spectroscopic data revealed that the type of interaction between Co-POM and support depends on the amount of anchored functional NH2-groups. It was found that Co-POM was attached to NH2-(CH2)(x)-SiO2 support both by the electrostatic NH3+center dot center dot center dot Co-POM- and dative (Si-OH center dot center dot center dot Co-POM) bonding. Both the amount of anchored NH2-groups and the distance between NH2-group and surface of silica affect the nature of the interaction between Co-POM and surface functional groups. The increase of the amount of anchored NH2-(CH2)(3)-groups leads to decrease in the contribution of dative bonding Si-OH... Co-POM and an increase in the contribution of electrostatic bonding NH3+center dot center dot center dot Co-POM-. The activity of the immobilized Co-POM was tested in benzyl alcohol oxidation with oxygen in CH3CN medium. It was found that catalytic activity and stability of Co-POM depend on the nature of interaction between Co-POM and surface groups of support that is adjustable both by the amount of anchored functional NH2-groups on silica support and the distance between NH2-group and surface of silica. (C) 2009 Elsevier B.V. All rights reserved.