The selective catalytic reduction (SCR) of NO was investigated by in situ diffuse reflectance infrared spectroscopy (DRIFTS) over catalysts based on iron-pillared clays (Fe-PILC) ion exchanged with copper. It was studied the influence of either total amount of metal or copper distribution as Cu2+ and CuO on the surface, with the aim to give a general idea of the reaction mechanism for this kind of catalysts. It was noted that the reaction intermediates were nitrates, nitrites, acetate, and CxHyOzN species. At low temperatures, bands corresponding to the vibration of C=C and COO- groups were observed for those samples with CuO in their structure, confirming that its presence improves the NO yield to N-2. (C) 2010 Elsevier B.V. All rights reserved.