(446b) Tuning the Molecular Design of Tertiary Amine Catalysts on Amorphous Mesoporous Silica Supports for Selective Glucose Isomerization and Acid-Base Cooperative Reactions

Amorphous silica materials offer a tunable, high surface area platform for creating heterogeneous catalysts. While mesoporous silica supports such as SBA-15 are presented as an idealized structure, real catalytic materials are quite complex and can have molecular interactions that facilitate some reactions while inhibiting others. The key challenge is understanding how these molecular interactions affect catalytic performance. Through combining molecular synthesis, advanced spectroscopy, and computational work, molecular interactions that occur in amorphous mesoporous silica are elucidated. Specifically, we investigate amorphous silica materials containing surface silanols that are functionalized through grafting organosilanes containing amines. We identify that the amine structure and loading as well as the catalyst structure strongly impact observed amine-silanol interactions. The observed amine-silanol interactions have implications for catalytic behavior observed for glucose isomerization and the Knoevenagel reaction. Through tuning the overall catalyst design, the overall catalyst activity and selectivity can be improved. Overall, these results provide unique insights on the nature of the surface interactions of the catalytic sites with the silica surface that improve our understanding of these materials.