Mesoporous MCM-41 molecular sieves with Si/M (molar) ratios of 100 containing platinum group metals (Pd, Pt, Rh. Ir) were synthesized by the hydrothermal method These catalysts were systematically characterized by various analytical a rid spectroscopic techniques, viz, XRD, TEM. DRUV-vis, N-2 sorption XRD analysis confirmed that the presence of platinum metals did not influence the parent structure and phase purity of the MCM-41 catalysts DRUV-vis spectral studies of MCM-41 indicate the presence of platinum metal ions The catalytic activities of these catalysts were evaluated for the reduction of NO by CO as a function of temperature The Study revealed that the catalytic activity is, in the order (Rh>Ir>Pd>Pt) Our experimental results are in good agreement with theoretical previous analysts based on the NO center dot dissociation activation energy. (C) 2009 Elsevier B V. All rights reserved