A new methodology for the modification of clays with the mixed Al–Fe and Al–Ce–Fe systems, which involves the synthesis of solid polymeric precursors and their use as pillaring agents in the modification of clays. The pillared clays using this new methodology show a catalytic activity and selectivity comparable to those of solids synthesized by the conventional method in a dilute medium. This paper proposes a new methodology for the modification of clays with the mixed Al–Fe and Al–Ce–Fe systems, which involves the synthesis of solid polymeric precursors and their use as pillaring agents in the modification of clays. The process of intercalation of clay with Al 13 , Al 13 + Fe and Al 13 + Ce + Fe nitrate was performed using ultrasound. The pillaring agents Al 13 , Al 13 + Fe and Al 13 + Ce + Fe were characterized by XRF, XRD, SEM and 27 Al NMR techniques, and pillared clays were characterized by XRF, XRD and N 2 adsorption to 77 K. The catalytic properties of pillared clays were evaluated using catalytic wet peroxide oxidation of phenol in dilute aqueous medium, demonstrating activity comparable to that of solids modified by the conventional method.