High surface area novel niobium mesoporous catalysts were synthesised via sol-gel method. The Nb-Al-MCM-41 catalysts characterised by BET, FTIR, ICP-MS, XPS and XRD. The Nb-Al-MCM-41 samples exhibited very large surface area of 2285 m(2)/g (pore volume 2.16 cm(3) g(-1)) and 1550m(2)/g (pore volume 1.83cm(3) g(-1)) with average pore diameter of 37.9 Angstrom (by BET) and 44.1 Angstrom, respectively. The adsorption and disproportionation of NO and CO over Nb-Al-MCM-41 mesoporous catalysts indicated the formation of various NO/CO species or complexes with active metal sites. The structure-dynamics of the metal activated complex and reactive species formed during the CO/NO reaction has been studied. The nitrous oxide, nitrite, mononitrosyl, nitrate and dinitrosyl species formation were observed after the NO adsorption over the Nb-Al-MCM-41 catalysts. CO adsorption at room temperature lead to the formation of up to six bands attributed to physisorbed carbon dioxide and cationic Lewis acid carbonyl moieties as well as transition metal carbonyl complexes. (C) 2004 Elsevier B.V. All rights reserved.