Post-synthetic modification of crystal-like periodic mesoporous phenylene-silica with ferrocenyl groups

Abstract

Amination of crystal-like 1,4-phenylene-bridged periodic mesoporous organosilica (Ph-PMO) was achieved with about 35% conversion of phenylene groups. Ferrocenylimine groups were subsequently anchored onto this material by condensation of acetylferrocene with amino groups. Elemental analysis indicated that about 15% of amino groups in PMO-NH2 were derivatized, resulting in an iron loading of 0.21 mmol g(-1). Evidence for the presence of ferrocenylimine groups in the derivatized material (PMO-Fc) was obtained from C-13 cross-polarization (CP) magic-angle spinning (MAS) NMR and FT-IR spectroscopies. PMO-Fc was further characterized by Si-29 MAS NMR spectroscopy, powder X-ray diffraction (XRD), N-2 adsorption-desorption, and thermogravimetric analysis (TGA). Powder XRD and N-2 adsorption-desorption data for PMO-NH2 and PMO-Fc indicated that the mesoporous structure and molecular-scale periodicity in PMO-NH2 were largely retained upon treatment with acetylferrocene. The material PMO-Fc was examined as a catalyst for the oxidation of styrene at 55 degrees C using hydroperoxides as oxidants. The reaction products were benzaldehyde (major) and styrene oxide (minor), with the aldehyde being formed in yields of 25-27% at 24 h. Recycling experiments indicated that the material was susceptible to leaching of catalytically active species into the liquid phase due to the pronounced water sensitivity of the azomethine linkage. (C) 2013 Elsevier B.V. All rights reserved.