The polymer coated magnetic nanoparticles has gained significant attention for potential applications in biomedicine, separations, and magnetic storage. In this study, beta-cyclodextrin-polyurethane polymer coated Fe3O4 magnetic nanoparticle as a novel class of hybrid organic/inorganic molecular catalyst was successfully prepared and evaluated as solid-liquid phase-transfer catalyst and molecular host system for nucleophilic substitution reactions. The nanocomposite has demonstrated the ability to catalytic the nucleophilic substitution reaction of benzyl halides with thiocyanate, azide, cyanide and acetate anions in water. No evidence for the formation of by-products for example isothiocyanate or alcohol was observed and the products obtained in pure form without further purification. The nanomagnetic polymer brush catalyst was easily removed from solution via application of a magnetic field, allowing straightforward recovery and reuse. Results obtained from scanning electron microscopy (SEM) and vibrating sample magnetometery (VSM) show that the synthesized magnetic nanocomposite are superparamagnetic with a mean diameter of 59 nm. The grafting of beta-cyclodextrin-polyurethane polymer to Fe3O4 magnetic nanoparticle is confirmed by Fourier transform infrared spectroscopy (FT-IR). (C) 2012 Elsevier B.V. All rights reserved.