Synthesis of ferrocenylazobenzene-functionalized MCM-41 via direct co-condensation method

Abstract

Ferrocenylazobenzene-functionalized mesoporous MCM-41 material (Fc-Az-M14), was synthesized directly through co-condensation of 4-triethoxysilyl-3′-ferrocenylazobenzene (TEFA) and tetraethyl orthosilicate (TEOS), under basic conditions, using cetyltrimethylammmonium bromide (CTAB) as structure-directing agent. The template was removed through solvent extraction, to yield the ferrocenylazobenzene-containing ordered mesoporous organosilicas Fc-Az-M41. The prepared material was characterized by nitrogen adsorption, X-ray diffraction (XRD), solid state 29Si MAS NMR and 13C CP-MAS NMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) and diffuse reflectance UV-Vis spectroscopy (DR UV). The results showed that Fc-Az-M41 had an ordered two-dimensional hexagonal mesostructure, high BET surface area and pore volume. The pore diameter, BET surface area, and pore volume of the extracted material were 3.8 nm, 1070 m2/g and 0.80 cm3/g, respectively. The mean pore diameters of MCM-41 clearly decreased by ca. 0.65 nm upon incorporation of Fc-Az groups. UV-Vis spectrum of Fc-Az-M41 was determined by a diffuse reflectance method after UV irradiation. The presence of the azobenzene chromophores in this material can be clearly observed in the DR UV-Vis spectra of surfactant-free Fc-Az-M41. This spectra shows that the framework of this material is formed predominantly by trans isomer, and the π-π* and the n-π* absorption bands were affected by metal-to-ligand charge transfer (MLCT).