An approach toward the synthesis of platelike ordered mesoporous materials from layered zeolite precursors

An ordered silicate mesophase has been synthesized via a hydrothermal treatment of a lamellar cetyltrimethylammonium-intercalated complex. The precursor was obtained by reaction of the layered silicate Na-RUB-18 with the cationic surfactant cetyltrimethylammonium chloride at pH 11.5. Hydrothermal transformation of this lamellar phase into an MCM-41-type mesoporous silicate was studied by powder X-ray diffraction, thermogravimetric analysis, Si-29 magic-angle spinning NMR, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. The as-prepared mesoporous product formed after 5 days of hydrothermal treatment retains the platelike morphology and most of the local ordering of the parent material. Removal of template by calcination drastically decreases the crystallinity, although lower temperature treatment with ozone partly preserved the crystalline structure. The final mesoporous material shows very thin platelike morphology, with MCM-41-type of channels perpendicular to the plates.