Metalloporphyrins immobilized on silica-coated Fe3O4 nanoparticles: Magnetically recoverable catalysts for the oxidation of organic substrates

Authors: Geani Maria Ucoski, Fábio Souza Nunes, Gilson DeFreitas-Silva, Ynara Marina Idemori, Shirley Nakagaki

Abstract:
In this paper we report the immobilization of different cationic and neutral metalloporphyrins (MPs) on silica-coated Fe₃O₄ nanoparticles, obtained by basic hydrolytic sol–gel process. We characterized the MPimmobilized materials by UV–vis spectroscopy (UV–vis), X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). We achieved 100% and 2% immobilization of cationic and neutral MPs, respectively. The strong electrostatic interactions between the hydroxylated surface of the silica and the positive charges of the cationic MPs favored immobilization of the charged MPs; the neutral MP probably established a weak bond with the silica and easily leached from the support. We investigated the catalytic activity of the immobilized MPs in the oxidation of cyclooctene, cyclohexene, and cyclohexane using iodosylbenzene as oxygen donor. We used the immobilized MPs in at least five successive cyclooctene oxidation reactions – the yields did not decrease, confirming that the catalyst can be reused. The synthesized catalysts displayed magnetic properties, which allowed their fast separation from the reaction medium using a simple magnet.

Keywords:
Porphyrin
Fe₃O₄
Immobilization
Silica
Sol–gel
Catalysis
Oxidation

Published in: Applied catalysis A: General  (Volume 459, Pages 1-130, 24 May 2013)

Publisher: Elsevier

ISSN Information: 0926-860X

Metalloporphyrins immobilized on silica-coated Fe3O4 nanoparticles: Magnetically recoverable catalysts for the oxidation of organic substrates

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