(344y) Enhancing Hydrophobicity and Catalytic Activity of Nano-Sn-Beta through Post-Synthetic Treatment with Fluoride

Elucidation of structure-function relationships can enhance the performance of catalytic materials used for a broad range of reactions relevant to biomass valorization and pharmaceutical production. After considerable focus had been on examining structure-function behavior of the catalytic site, it has become increasingly evident that molecular interactions beyond the catalytic site in the outer sphere, such as solvation, significantly impact catalytic activity. The key challenge is to control this catalytic reaction environment. In this work, a highly active catalyst is achieved by tuning the molecular interactions of the catalyst with the substrates through post-synthetically modifying the hydrophobicity of the material. First, nano-Sn-Beta is synthesized through a hydrothermal route and is used to overcome diffusion limitations that were observed for conventional Sn-Beta. While conventional Sn-Beta is synthesized in the presence of fluoride to create materials with few defects and large crystals, the synthesis of nano-Sn-Beta utilizes hydroxide as the mineralizing agent, leading to smaller crystals that are more hydrophilic because of the greater number of silanols. Building on the few examples that modify the hydrophobicity of MFI, we propose a method that utilizes a post-synthetic treatment of the calcined nano-Sn-Beta with tetraethyl ammonium fluoride (TEAF) to heal defects and reduce the silanol content throughout the crystal, thereby increasing its hydrophobicity. The treated catalyst exhibits a significant increase in catalytic performance (70% increase in TOF0) over the untreated material for the Lewis acid catalyzed epoxide ring opening with alcohols. Enhancing the hydrophobicity of nano-Sn-Beta can increase the stability of the catalyst as well as the scope for different chemical reactions. Overall, this work will demonstrate the post-synthetic modification of nano-Sn-Beta to produce a hydrophobic zeolite framework and the effect of hydrophobicity on catalytic activity and selectivity.