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ESR characterization of vanadium centers supported on Al-containing mesoporous silica

Abstract:

The properties of Al-substituted mesoporous silicas modified with VO2+ ions in a one-step exchange reaction in aqueous medium have been investigated by means of ESR. The vanadium centers exist at the surface in a well dispersed form. ESR identifies two types of vanadyl ions: (a) fully hydrated VO2+ ions, retaining motional freedom at room temperature, and (b) species firmly bound to the surface due to the formation of inner-sphere complexes. The contribution of the latter increases with A1 substitution. The phenomenon is discussed in terms of a gradual modification of the surface properties as a result of A1 incorporation. © 2001 Elsevier Science B.V. All rights reserved.