Cu-ion-exchanged iron-pillared interlayer clays (Fe-PILCs) were prepared under different pH conditions to analyze the influence on the distribution of the copper species over their structure, and on the catalytic performance for the selective catalytic reduction (SCR) of NOx by propene. It was observed that for those samples prepared without pH control, the copper was as isolated Cu2+ ions. When the samples were prepared under acid pH, the catalytic activity decreased and an appreciable CO production was observed, likely due to the low amount of Cu2+ cations in those catalysts. Finally, for the samples prepared under alkaline pH, the copper was as Cu2+ ions and CuO clusters. Their catalytic tests showed the best results for the SCR of NOx The presence of CuO species led to an improvement in NOx yield to N-2. With the catalytic tests and a study by in situ FTIR of SCR of NO, a reaction mechanism has been proposed, where the reaction intermediates are mainly acetates, organic nitro compounds and nitrous oxide species. (c) 2006 Elsevier B.V. All rights reserved.u