The nitroxides 1 and 1-oMe were employed as EPR probes for the investigation of the supramolecular structures and dynamics of organic molecules adsorbed on the external surfaces of two MFI zeolites (silicalite and ZSM-5). The results for the two zeolites are qualitatively similar, but depend quantitatively on the surface area of the external surface. Computational analysis of the EPR spectra as a function of loading of the probe is consistent with an initial strong association of the probes with the holes on the external surface, followed by a weaker binding to the framework of the external surface between the holes. The first supramolecular structure (binding to holes) fixes the motion of the probes and allows for an estimation of the average separation of the probes through EPR analysis of the dipole-dipole interaction. After saturation of the holes and the onset of the second supermolecular structure (binding to the framework), rapid diffusion of the probes on the framework occurs and provides a means for an estimation of the motion of the probe through EPR analysis of the spin-spin exchange interaction. The mobile framework's probes collide and displace the probes in the holes, resulting in a dynamic equilibrium between probes at both sites. The displacement of the nitroxides associated with the holes by three coadsorbed "displacer" molecules, 2, 3, and 4, was investigated by the change of the probe EPR. Addition of ketones 2 and 4 resulted in the displacement of nitroxides after sufficient displacer was added to saturate the holes on the external surface. This result is consistent with a stronger binding of the nitroxide to the surface and for the need for molecules of 2 and 4 to be situated on the framework before displacement of the nitroxide can occur. Compared to 2 and 4, 3 is found to be a poor displacer of nitroxide because of its weak association with the holes. From the competitive displacements, it is concluded that the binding to the external surface increases in the series 3 < 2 < 4 much less than 1, being at a minimum for the nonpolar 3 and a maximum for the nitroxide that possesses two polar moieties for interaction with the zeolite surface. On the basis of these results, a model was developed which described the supramolecular structures and dynamics formed by the ketones and MFI zeolites at a function of loading and for the various systems investigated.