One-pot synthesis of core–shell silica–aluminosilicate composites: Effect of pH and chitosan addition

Mesoporous silica–aluminosilicate composites have been successfully synthesized via a sol–gel process under acidic (pH 6.5) and basic (pH 11.5) conditions using cetyl trimethylammonium bromide (CTAB) as a template and chitosan as a domain size controller. The synthesized products were characterized by using Fourier Transform Infrared (FTIR) Spectroscopy, solid state 27Al CP/MAS NMR Spectroscopy, small angle X-ray Diffraction Spectroscopy (SAXS), nitrogen sorption measurement and Transmission Electron Microscopy (TEM). Through one-pot synthesis, the uniform infiltration of mesoporous aluminosilicate in mesoporous silica was formed under strong basic conditions (pH 11.5), while self-assembled core–shell silica–aluminosilicate composites having an ordered mesoporous silica core and mesoporous aluminosilicate shell were achieved under mild acidic conditions (pH 6.5). Moreover, mesoporous silica–aluminosilicate composites of more uniform, smaller domain size and higher macroporosity were obtained when chitosan was applied.