Immobilized late transition metal complexes based on salicylaldimine ligands were used as catalysts in the wet air hydroxylation of phenol in the presence of hydrogen peroxide. Three metals, viz. cobalt, nickel and copper, and two different kinds of supports, namely, amorphous silica and mesoporous MCM-41, were employed. The effect of pH on the hydroxylation process was also investigated. It was observed that the regioselectivity of the hydroxylation process strongly depends on the kind of support employed. (C) 2006 Published by Elsevier B.V.