Jiangwei Song

High-temperature synthesis of ordered mesoporous silicas from solo hydrocarbon surfactants and understanding of their synthetic mechanisms

Ordered mesoporous silicas (SBA-15 or MCM-41) have been directly hydrothermally synthesized at high temperatures (160–180 °C) by using a solo hydrocarbon surfactant (P123 or CTAB). 1H NMR spectra and thermogravimetric (TG) curves showed that these hydrocarbon surfactants decomposed during the preparation process at such high temperatures. Accordingly, we proposed that the surfactant micelle plays an important role during the cooperative self-assembly of the silicates and surfactants in the initial stage for the formation of basic mesostructure, and it is no longer indispensable in the subsequent hydrothermal treatment at high temperature.

Highly Steam-Stable Mesoporous Silica Assembled from Preformed Zeolite Precursors at High-Temperatures

Mesoporous silica (JLU-20-S) is successfully synthesized at high-temperatures (180–220 °C) by the assembly of preformed silicalite-I zeolite nanoclusters with a mixture of triblock copolymer surfactant (P123) and fluorocarbon surfactant (FC-4). The preformed silicalite-I nanoclusters are obtained by heating, at 100–120 °C for 2–3 h, silica gels at SiO2/(TPA)2O/H2O molar ratios of 1/0.14/36. Mesoporous JLU-20-S shows extraordinary stability in steam (800 °C, 4 hours), compared with other mesoporous silica materials (JLU-20 synthesized at 190 °C, MPS-9 prepared from preformed silicalite-I zeolite nanoclusters at 100 °C, and SBA-15). The results of X-ray diffraction and transmission electron microscopy show that JLU-20-S has a hexagonal mesoporous symmetry, and the data obtained from N2 isotherms show that JLU-20-S contains both mesopores and micropores. The high steaming stability of the mesoporous silica of JLU-20-S is possibly related to synergistic advantages of both high-temperature synthesis and preformed zeolite nanoclusters in the synthesis of ordered mesoporous silica materials, and the observed microporous volume in JLU-20-S is attributed to the use of preformed zeolite nanoclusters.

Anion-exchangeable inorganic-organic hybrid materials synthesized without using templates

Inorganic-organic hybrid materials have been obtained at room temperature in aqueous solution without using the templates of surfactants. The materials are carefully characterized by anion-exchange measurement, elements analysis, X-ray diffraction, and infrared spectroscopy. Notably, the anion-exchange capacity of the samples (3.9 mmol·g−1) is even higher than anion-exchangeable resins. Interestingly, both small and large anions could be easily exchanged into the samples due to the plasticity of the samples, along with the phase transition.