Hierarchical mesoporous silica microspheres as unique hard-template for preparation of hierarchical mesoporous TiO2 microspheres with trimodal mesoporosities via nanocasting

Abstract This work for the first time reported that hierarchical meso-mesoporous SBA-15 silica microspheres (HMM-SiO 2 -MSs) can serve as a unique and suitable hard-template for the nanocasting preparation of mesoporous TiO 2 with both hierarchical mesostructures and well-preserved microsphere particle morphology. A two-step impregnation (TSI) method was developed and customized and its effectiveness was studied in comparison with the single-step impregnation method. Trimodal mesoporosities and their origin are newly recognized and analyzed. The materials were examined by various techniques, including the FE-SEM, N 2 sorption, TEM and XRD. Under optimized conditions, the hierarchical mesostructures and spherical particle morphology of HMM-SiO 2 -MSs can be replicated for HMM-TiO 2 -MSs. The high surface area and pore volume of HMM-TiO 2 -MSs reach 194 m 2  g -1 and 0.68 cm 3  g -1 , respectively, with the latter more than twice those templated by conventional SBA-15s. Besides HMM-TiO 2 -MSs, such HMM-SiO 2 -MSs as hard-template might be extended to the preparation of other materials with hierarchical mesostructures.