Independent Fine-Tuning of the Intrawall Porosity and Primary Mesoporosity of SBA-15

We present a study in which the intrawall porosity and primary mesoporosity. of SBA-15 are independently controlled by modifying the strength of the molecular interaction that governs the formation of the material. The interactions are targeted at specific times during the process of formation, which results in selective tuning of the porosity, while other characteristics of the SBA-15 material are retained. We show that the intrawall porosity can be considerably reduced by addition of NaI, but not NaCl, and that the shape of the primary mesopores can be influenced by a decrease in temperature, while while the two-dimensional hexagonal structure and the particle morphology and size remain unchanged. The timing of the "tuning event" is imperative. We show that a decrease in intrawall porosity by addition of NaI is generic to Pluronic-based mesoporous silica syntheses. This work demonstrates that the material characteristic of mesoporous silica is not necessarily restricted by the initial synthesis conditions as the material properties can be tuned by "actions" taken upon the ongoing synthesis. The triblock copolymer Pluronic P104 was used as a structure director and tetramethyl orthosilicate as a silica source. The materials have been characterized primarily with nitrogen sorption and small angle X-ray diffraction.