In this paper, we compare the properties and activities of immobilised forms of in situ formed cobalt-acetato complexes of pyridin-4-ylmethyl-(3-triethoxysilanyl-propyl)-amine (PYPA) on organomodified hexagonal mesoporous silica (HMS) prepared via different routes, namely sol-gel synthesis, post-modification of sol-gel AMP-HMS, and grafting. All materials are able to act as host for cobalt-acetato complexes to different extents, and are able to catalyse the aerial oxidation of styrene. The support materials and catalysts were characterised by DRIFT, X-ray photoelectron spectroscopy (XPS), N-2 adsorption and elemental analysis, and compared with their homogeneous counterpart and a material obtained by grafting of a complex formed prior to immobilisation on the silica surface. (C) 2003 Elsevier B.V. All rights reserved.