Structural evolution of SiO2–ZrO2 nano-sol intercalated clays upon pillaring reactionElectronic supplementary information (ESI) available: BJH pore size distribution and k3-weighted EXAFS spectra of the SiO2–ZrO2 sol-pillared clay at different calcination temperatures. See http://www.rsc.org/suppdata/jm/b2/b208929g/

Abstract

A two-dimensional layered nanohybrid with a high specific surface area has been prepared by ion exchange reactions between the sodium ions in montmorillonite and the positively charged Zr-coated SiO2 sol particles. The basal spacing increases from 12.5 A to 26 A upon intercalation due to the insertion of a SiO2–ZrO2 nano-sol into the interlayer space of montmorillonite. Upon calcining at 300 °C, it transforms into a porous nanohybrid with a basal spacing of 22.6 A. The N2 adsorption–desorption isotherms were characterized as being of type IV according to the BDDT classification, indicating the existence of a large number of micro- and mesopores. From its hysteresis curves, one can classify the nanohybrid as being of the H3 type with slit-shaped pores by the IUPAC classification. The estimated BET specific surface area and average micropore size are about 358 m2 g−1 and 12 A, respectively, with the latter value is similar to the gallery height of the sample indicating that the SiO2–ZrO2 sol particles are intercalated to form a monolayer. The local structural evolution of the Zr species in SiO2–ZrO2 sol particle has been investigated systematically by X-ray absorption spectroscopy at the Zr K-edge with respect to the calcination temperature. The EXAFS spectroscopic results confirm that the surface of the nano-sized SiO2 sol particles is coated with the Zr species.