Preparation of hierarchically mesoporous silica microspheres with ordered mesochannels and ultra-large intra-particulate pores

Abstract In this work, hierarchically mesoporous silica (HMS) microspheres with ordered mesochannels and ultra-large intra-particulate pores are for the first time prepared via a ternary nonionic surfactant templating system (TEOS/P123/HCl(aq.)). Several crucial experimental parameters pertaining to the employed partitioned cooperative self-assembly process and their roles in shaping the mesostructures and morphology were investigated. It was found that relatively low synthesis temperatures, optimal at 36 °C, lead to much improved meso-ordering in the 1st mode mesostructures, while partitioned addition combinations of silica precursor ( e.g. , 6/4 combination) at such temperatures show to play an important role in inducing spherical particle morphology. By simply increasing the hydrothermal treatment (HTT) temperature up to 140 °C, enhanced porosity together with ultra-large intra-particulate pores can be obtained without compromising meso-orderings, depending mainly on the HTT induced mesostructural transformation process. Higher HTT temperature causes the fragmentation in the 1st mode mesostructures and disappearance of meso-orderings. The resultant micro-sized HMS spheres reveal certain clew-like features: the ‘yarns’ comprise bundles of ordered mesochannels (1st mode mesopores, ca. 8–12 nm), while the 2nd mode intra-particulate pores ( ca. 33–128 nm in sizes) exist between the intertwined ‘yarns’. Such HMS microspheres with tunable porous structures might find some interesting applications in chromatographic separations and controlled delivery, etc.