Influence of synthesis parameters on the formation and structure of bimodal mesopore silica in a controlled sol-gel process

In the present work, a series of synthesis parameters, including those that may affect the size of surfactant micelles and that may affect the relative rate of hydrolysis and condensation of tetraethyl orthosilicate (TEOS), were judiciously adjusted to study their direct influence on the formation and structure of our previously reported bimodal mesopore silica (designated as BMS). It is found that both the framework and textural mesopores of BMS silica can be tailored over a fairly wide size range, but on the whole the textural mesopore size is more sensitive to the change of the synthesis parameters than that of the framework mesopore size. The change of three synthesis parameters, such as increasing the amount of ethanol, decreasing the chain length of surfactant or increasing the alkali/silica molar ratio, would lead to the mesostructure of the silica obtained to transform from initial BMS into MCM-41.