Simple Quaternary Templating Systems for Direct Synthesis of Unique SBA-15 Mesopore Frameworks Embedded with High-Content TiO2 Nanoparticles as High-Performance Photocatalysts

This work presents a simple P123-based quaternary templating system using titanyl sulfate (TS) as the TiO2 precursor and self-contained sulfuric acid as the catalyst (TS/TEOS/P123/H2O). A unique structural configuration of SBA-15-type mesopore frameworks embedded with high-content TiO2 nanoparticles can be directly obtained. Even with a high TiO2 content (29.1 wt %), well-defined mesostructures free of pore blocking can be secured. A new structural formation mechanism is unveiled: a self-assembly process between inorganic species and P123 micelles yields ordered mesostructures catalyzed by self-contained TS in the low-temperature step, while sol-gel reaction and crystallization of TS coincide with processes of mesostructural re-organization and partial evacuation of P123 from mesopores. The incorporation of high-content TiO2 nanoparticles into mesopore frameworks mainly happens during the hydrothermal treatment step. Not surprisingly, thanks to well-defined mesostructures containing high-content accessible TiO2 nanoparticles, such TiO2/SBA-15 composites show high activity and good reusability in photodegrading Rhodamine B and humic acids and photoreducing highly toxic Cr6+ in water under UV irradiation.