Copper ion-exchanged and impregnated iron-pillared interlayer clays (Fe-PILCs), prepared by using copper solutions with different pH values and copper precursors, were tested in the selective catalytic reduction (SCR) of NOx by propene. Low pH values led to dehydroxylation of the iron pillars and damages in the clay structure. Samples prepared without pH control presented isolated Cu2+ ions; those prepared by using alkaline pH solutions presented Cu2+ ions and CuO clusters. It was observed that the presence of Cu2+ ions accompanied by CuO clusters led to an improvement in the NOx yield to N-2, which was in agreement with the best activity for C3H6 combustion showed by these catalysts. The best catalytic results were obtained with samples prepared by ion exchange with copper II acetate under alkaline pH, where Cu2+ ions and CuO clusters were simultaneously formed in an adequate proportion. (c) 2006 Elsevier B.V. All rights reserved.