Large-pore cubic Ia-3d mesoporous silicas: Synthesis, modification and catalytic applications

Large-pore cubic Ia-3d mesoporous silicas were synthesized by co-condensation of tetraethoxysilane (TEOS) and a small amount of phenyltriethoxysilane (PTES) under acidic conditions using triblock copolymer P123 (EO20PO70EO20) as the template. In the synthesis procedure, the amount of PTES added in the range of 3.0–10% was very vital for the formation of the ordered Ia-3d structure. In addition, the prehydrolysis of PTES prior to TEOS in the template solution was also important for the preparation of ordered Ia-3d materials. If TEOS was prehydrolyzed, ordered 2d-hexagonal materials were obtained. After mild calcination at 250 °C to selectively remove the template, Ia-3d and 2d-hexagonal materials with 10% PTES were selected to be sulfonated to introduce sulfonic acid sites into the channels. Both Ia-3d and 2d-hexagonal mesoporous sulfonic acid catalysts can effectively catalyze the liquid phase condensation reaction of phenol with acetone to Bisphenol A. The catalytic activity of the Ia-3d catalyst was slightly higher than that of the 2d-hexagonal one. Additionally, after calcination at 550 °C to remove the template and phenyl groups, Ia-3d mesoporous materials with different pore sizes (3.8–6.8 nm) were further functionalized with amino groups by postsynthesis grafting. It was found that in the synthesis of flavanone the catalytic performance of amino-functionalized Ia-3d mesoporous base catalysts increased with the increase in their pore sizes.

Graphical abstractLarge-pore cubic Ia-3d mesoporous silicas were synthesized by co-condensation of tetraethoxysilane and phenyltriethoxysilane under acidic conditions. In the synthesis, the amount of PTES added and the prehydrolysis of PTES prior to TEOS were very vital for the formation of the ordered Ia-3d structure. By further modifications, sulfonic acid sites and amino groups were respectively introduced into the channels of Ia-3d mesoporous materials. These Ia-3d mesoporous acid and base catalysts were found to be very efficient in the synthesis of Bisphenol A and flavanone, respectively.Figure optionsDownload full-size imageDownload as PowerPoint slide