High-temperature synthesis of stable ordered mesoporous silica materials using mesoporous carbon as a hard template

Replicated mesoporous silica materials from CMK-3 (denoted as RSC-3-X, X stands for synthesis temperature) have been successfully synthesized in acidic media at high temperatures (160-240 °C) and subsequently characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen sorption isotherms, and 29Si nuclear magnetic resonance (NMR) spectroscopy. XRD patterns and nitrogen sorption isotherms exhibit the highly hydrothermal stable mesostructure of RSC-3 samples. Transmission electron microscopy images of RSC-3-220 show ordered hexagonal arrays of mesopores with 1D channels and further confirm the 2D hexagonal (p6mm) mesostructure of RSC-3-220. 29Si MAS NMR spectra indicate that as-synthesized RSC-3 samples are primarily made up of fully condensed Q4 silica units (δ = −112 ppm) with a small contribution from incompletely cross-linked Q3 (δ = −102 ppm) as deduced from the high Q4/Q3 ratio of 5.5-9.5, implying the fully condensed walls of RSC-3. Such unique structural features should be attributed directly to the high-temperature synthesis, which could be responsible for the observed highly hydrothermal stability of RSC-3.