Molecular beam scattering techniques have been combined with several thermal desorption spectroscopy experiments to address the structure-activity relationship (SAR) for a metal oxide system. The adsorption of CO2 on pristine and intrinsic defect sites, respectively, could be consistently distinguished with all experimental techniques. Furthermore, by a simple methodology, namely the preadsorption of hydrogen, defect sites could specifically be blocked. The binding energies depend distinctly on the adsorption site, i.e. a kinetic SAR was present. (C) 2004 Elsevier B.V. All rights reserved.