Recent development of various templating techniques has led to the chemical preparations of porous materials with ordered arrays of uniform pores with diameters from several nanometers to micrometers. Materials with bimodal pore size distribution are expected to utilize the benefits of each pore size regime. The dual-templating methods was used in this work to prepare the silicates having not only mesopores but also macropores. The macropores were made by colloidal crystal templating method using polystyrene spheres with anion groups on the surface, while the mesopores were prepared by supramolecular templating method with organic templates leading to the mesoporous structures of MCM-41, HMS, and SBA-15, respectively. The packing modes of latex templates and the skeletal silica were observed by SEM, the macropores and mesopores were observed by TEM, and the pore size distribution and pore volume were measured by $N_2$ Adsorption.
The resulting silicates have interconnected macropores with the same geometry to the original template spheres with uniform size and shape. The walls of macropores contained uniform and ordered mesopores. The mesopores made by ionic template, neutral amine and amphiphilic triblock copolymers had their corresponding mesoporous structures of MCM-41, HMS, and SBA-15, respectively.
The mesopores were formed partially when the MCM-41 mother liquor was just filtered over the packing of the spheres without sonication and hydrothermal treatment. When the solution was infused by sonication, the mesoporous structure was not ordered. The silicates with macropores and mesopores of HMS and SBA-15 had higher surface area than the silicates containing HMS mesopores only. Filtration was more effective for infusing mother liquor of HMS and SBA-15 than sonication because the driving force for penetration can be provided via suction of aspirator connected to the filter apparatus.
