Acidity-dependent mesostructure transformation of highly ordered mesoporous silica materials during a two-step synthesis

Highly ordered mesoporous silica materials have been synthesized under mildly acidic conditions by templating with a nonionic triblock copolymer (Pluronic P104) in a two-step process. It was found that a transformation from the SBA-15 type 2-dimensional (2D) hexagonal channel mesostructure (p6mm symmetry) to the MSU-X type 3-dimensional (3D) worm-like mesostructure could be induced by varying the pH whilst keeping all other conditions constant. The transformation between two types of mesoporous silica materials can be attributed to the effect of varying proton concentration on the interaction between organic micelles and inorganic species. Both types of mesoporous materials have high surface areas, large pore volumes, thick pore walls, large mean pore sizes, and narrow pore size distribution.