Transition metal and organic functionalization of hollow zeolite structures

Hollow zeolites with the MFI framework were selectively functionalized with transition metals, such as copper and vanadium, and organosilanes, such as aminopropyltriethoxysilane (APTES). The resulting hollow zeolite structures consist of a shell that has the characteristic porosity and ion-exchange properties of the parent zeolite and interior and exterior surfaces that are functionalized. In this study, strategies for selectively functionalizing the interior of the hollow zeolite structures and the zeolite shell are described as a method for tailoring the chemical properties of these materials. The first strategy involves functionalization of the mesoporous silica template with copper, vanadium and APTES in order to prepare hollow zeolite structures with encapsulated transition metals or organic functional groups. The second strategy involves post-synthesis modification of the zeolite hollow structures through transition metal ion-exchange of the aluminosilicate hollow shell. The resulting materials were extensively characterized by scanning electron microscopy, powder-X-ray diffraction, X-ray photoelectron spectroscopy, BET adsorption isotherms, electron paramagnetic resonance, and solid-state magic angle spinning NMR. The encapsulated transition metal ZSM-5 tubes exhibited similar transition metal local electronic environments but lower transition metal incorporation relative to the exchanged ZSM-5 tubes. (C) 2007 Elsevier Inc. All rights reserved.