Plugged hexagonal templated silica (PHTS): An in-depth study of the structural characteristics

Hexagonal mesoporous silica materials (PHTS) are synthesized with a high TEOS/EO20PO70EO20 ratio containing microporous nanocapsules or plugs inside the mesoporous channels. This PHTS material exhibits a tunable amount of open and plugged pores, has a high micropore volume (up to 0.24 mL/g), and is more stable than conventional micellar templated structures known so far. This study focuses on a thourough investigation of the influence of the amount of TEOS, the stirring temperature, the aging temperature, and the stirring time on the material characteristics using N-2 sorption, X-ray diffraction, and scanning electron microscopy. PHTS materials with different amounts of TEOS were synthesized at stirring temperatures between 60 and 100 degreesC. At 60 degreesC, materials synthesized with a molar ratio TEOS/P123 of 125 proved to have a more rigid silicate framework than materials synthesized with lower amounts of TEOS resulting in PHTSs with a smaller diameter. The amount of TEOS and the stirring temperatures proved to play an important role in the material formed. Unlike SBA-15, the micropore volume of PHTS tended to increase with increasing temperature where the maximum value was found for the highest amount of TEOS used (TEOS/P123 = 125). The influence of the aging temperature on the structural characteristics of PHTS is the same as that of the stirring temperature but less pronounced. An aging temperature of 80 degreesC improved the structural characteristics greatly and also enlarged the particle size, whereas 4 h was shown as the minimum stirring time required.