Porous Al2O3 presenting a specific surface area of S-BET = 105 m(2) g(-1) was coated with 3-N-propylpyridinium chloride silsesquioxane polymer. The ion exchange capacity of this polymer grafted onto an Al2O3 surface, resulting in a material designated as AlSiPy+Cl-, was 1.09 mmol g(-1). Furthermore, a cobalt(II) tetrasulfophthalocyanine anionic complex was immobilized on the chemically modified surface by an ion exchange reaction with a yield of 40 mumol g(-1) (the surface density of the electroactive species is 3.80 x 10(-11) mol cm(-2)). The electrochemical properties of the material obtained, AlSiPy/CoTsPc, were tested for the catalytic oxidation of oxalic acid at 0.77 V vs SCE in 1.0 mol l(-1) KCl solution. Furthermore, a chronoamperometric technique was used with the electrode to test its potential use as a sensor for oxalic acid. The electrode response to oxalic acid concentrations between 1.0 and 3.5 mmol l(-1) was linear with an estimated detection limit of 0.5 mmol l(-1). The charge transfer resistance of the material, measured using the electrochemical impedance spectroscopy technique, was 43 Omega cm(2). (C) 2004 Elsevier Inc. All rights reserved.