Time-resolved in situ X-ray absorption spectroscopy studies on an activated H5[PV2Mo10O40] oxidation catalyst were performed to obtain correlations between the dynamic structure and the catalytic selectivity of the material. Both the geometric and electronic structures of the vanadium and molybdenum metal centers of the catalyst change dynamically under the reaction conditions used. Moreover, the selectivity of the catalyst exhibits a pronounced correlation with the degree of reduction and the solid-state kinetics of the reoxidation process. The corresponding extent of reoxidation curve can be simulated with a solid-state kinetic model assuming three-dimensional diffusion as the rate-limiting step. Thus, the partially reduced catalyst exhibits a rate constant of the bulk-diffusion limited reoxidation, coinciding with the temporal evolution of the selectivity of the catalyst. (C) 2007 Elsevier Inc. All rights reserved.