Quantum chemical calculations were carried out to determine geometries, vibrational frequencies and adsorption energies of NO, NO2, N2O, and SO2 molecules on a gold-exchanged mordenite catalyst (Au/MOR). The results show that the adsorption energies are greater on [Au](+) than on [Au-3](+) species. In general, the charge transferred from Au to the adsorbed molecules is higher for [Au-3](+) than for [Au](+). It is shown for first time, that the SO2 adsorption is thermodynamically favored on the [Au](+) species, but not on [Au-3](+) species. Therefore at low Au content, the Au/MOR catalyst could be able to adsorb SO2. (C) 2012 Elsevier B.V. All rights reserved.