Porous materials with ordered uniform pores with diameters from several nanometers to micrometers have been obtained by various templating techniques. Materials with bimodal pore size distribution are expected to provide multiple benefits due to the combination of different pore size regimes. A new dual-templating method of preparing the macrostructured mesoporous silicates was used in this work. Powdered polystyrene templates were directly added into the surfactant solution for the synthesis of MCM-41, SBA-15 and KIT-1. The latex templates and the skeletal silica were observed by SEM, the mesoporous structures of silicates were confirmed by XRD patterns and $N_2$ adsorption analysis, and macropores and mesopores were observed by TEM.
The resulting silicates had the corresponding mesoporous structures of MCM-41, SBA-15, and KIT-1, respectively. The silicates with mesophase of MCM-41 exhibited the three dimensionally ordered and interconnected macropore structure designated skeleton structure. The silicates having mesoporous structure of SBA-15 had random packed macropores in the domains. Silicates synthesized by adding polystyrene templates into the synthesis gel of KIT-1 revealed the two kinds of structure. The biporous silicates had both the highly ordered macroporous structure and hollow spherical morphology. In addition, worm-like mesopores of KIT-1 were observed throughout the walls of spheres. The coexistence of macropores and mesopores in the resulting silicates were clearly confirmed by TEM images.
The characteristics of pore structure in the macrostructured MCM-41 was controlled by changing the synthesis conditions such as particle size or the amount of templates. The skeleton structure was revealed in the resulting silicates when the polystyrene beads with diameter above the range of 200 nm were used. The thickness of macroporous wall increased as the size of particle increased. As the amount of polystyrene templates to Si source was increased, hysterisis at higher relative pressures was developed in the $N_2$ adsorption isotherms. This indicated that the portion of macropores was expanded in the silicates.
