Fe(III) imidazole or histidine complexes were immobilized in porous matrices (montmorillonite and MCM-41) via two methods (introduction of preformed complex and complex formation within the ion-exchanged host substances). It was found that immobilization was successful only by the latter method. Immobilization increased the catalytic activity and catalyst life time in the decomposition reactions of hydrogen peroxide relative to the matrix-free complexes. The immobilized materials were characterized by various physicochemical methods.