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Article

Role of the Alkyl−Alkoxide Precursor on the Structure and Catalytic Properties of Hybrid Sol−Gel Catalysts

Alexandra Fidalgo,^† Rosaria Ciriminna,^‡ Laura M. Ilharco,*^† and Mario Pagliaro*^‡

Centro de Qumica-Fsica Molecular, Instituto Superior Tcnico, Complexo I, Avenida Rovisco Pais 1, 1049-001 Lisboa, Portugal, and Istituto per lo Studio dei Materiali Nanostrutturati, CNR, via Ugo La Malfa 153, 90146 Palermo, Italy

Chem. Mater., 2005, 17 (26), pp 6686–6694

DOI: 10.1021/cm051954x

Publication Date (Web): November 24, 2005

†

Instituto Superior Técnico.

‡

Istituto per lo Studio dei Materiali Nanostrutturati, CNR.

To whom correspondence should be addressed. E-mail: lilharco@ist.utl.pt (L.M.I.); mario.pagliaro@ismn.cnr.it (M.P.).

Abstract

Detailed diffuse-reflectance infrared Fourier transform structural analysis of a series of organically modified silicates (ORMOSIL)-entrapped catalysts, varying the molar percentage and the alkyl chain length of the organic group, shows that the important factors affording optimal catalytic performance are two: predominance of six-member siloxane rings (above 80% alkylation) and a low hydrophilicity−lipophilicity balance (HLB). These results provide investigators engaged in developing novel catalysts based on the sol−gel routean advanced chemical technology for synthetic organic/inorganic chemistrywith general guidelines to prepare optimal catalytic materials for a number of relevant applications.