Aluminosilicate obtained by sol–gel process as support for an anionic iron porphyrin: Development of a selective and reusable catalyst for oxidation reactions

Abstract

An anionic iron(III) porphyrin was immobilized on a synthetic aluminosilicate obtained by the sol–gel process and used as catalyst in the oxidation of organic substrates. Aluminosilicate was prepared by modification of a method previously described in the literature, using an ethanol/water solution of AlCl 3·6H 2O and Si(OC 2H 5) 4 (TEOS). Iron(III) porphyrin immobilization was carried out using magnetic stirring and reflux, and a good immobilization rate (88%) was obtained. Immobilization of a neutral iron(III) porphyrin on the solid was also tested, without success. The obtained materials were characterized by ultraviolet–visible and infrared spectroscopies, X-ray diffraction, TGA analysis, nitrogen absorption, and electron paramagnetic resonance (EPR). The catalytic activity of the immobilized iron(III) porphyrin was evaluated in the oxidation of cyclooctene, cyclohexane, and n-heptane, using iodosylbenzene as the oxygen donor. The results obtained in the present study show that the novel immobilized catalyst is a promising system for efficient and selective oxidation reactions. Besides that, the stable interaction between the iron(III) porphyrin complex and the support enables reuse of the heterogeneous catalyst.