SBA-15 surface functionalization via ferrocenyl Fischer chromium carbene coatings: Technology and textural properties

A ferrocenyl Fischer chromium carbene complex has been covalently grafted on the SBA-15 surface. The method of synthesis of this carbene is a classical one while the surface attachment of such compound on the SBA-15 pores is made via a bridging molecule of 3-aminopropyltriethoxysilane. Important physicochemical properties (XRD, TEM, and N2 sorption) of the preceding substrate, which involves the extra benefit of chemically adhering two transition metals (Fe and Cr) to the SBA-15 surface, are herein presented. The creation of covalent bonds between the silica surface and the ferrocenyl chromium carbene molecules is confirmed by FTIR spectroscopy. The pore size distributions of unfunctionalized and functionalized SBA-15 substrates (determined by N2 sorption) shed light about two issues: (i) a diminution of the pore width, surface area, and total pore volume (with respect to that existing in the uncoated SiO2 material) when ferrocenyl chromium carbene molecules are grafted to the pore surface; and (ii) the possibility of approximately knowing the thickness of the grafted layer of molecules. Calcination of the functionalized SiO2 substrate at 500 °C reincreases the free pore diameter and sharpens the pore size distribution while preserving the cylindricity of the pore walls.