Pillaring of high charge density synthetic micas (Na-4-mica and Na-3-mica) by intercalation of oxides nanoparticles

Porous metal oxides synthesized by pillaring the high charge density synthetic micas, Na-4-mica and Na-3-mica, were reported for the first time. The interlayer spaces of mica layers are pre-expanded with n-octylammonium cation, which are subsequently replaced by pillar precursors (iron polyhydroxy cation or Fe3+-deposited silica sols) to form intercalation compounds. Heating the precursors at 773 K resulted in the formation of Fe2O3 or Fe2O3–SiO2 pillared micas having a high surface area (57–130 m2/g), high porosity and good thermal stability. Characterization with XRD, TEM, and N2 adsorption experiments suggests that the resultant pillared micas consist of fragmented pillared clay forming a “house-of-cards” structure. The acidic property of the pillared micas was tested by TPD of ammonia, and the result shows that pillaring of Na-4-mica with Fe2O3 or Fe2O3–SiO2 causes a significant increase in the acid amount.