Surface-functionalized TUD-1 mesoporous molecular sieve supported palladium for solvent-free aerobic oxidation of benzyl alcohol

Palladium catalysts supported on TUD-1 mesoporous molecular sieves functionalized with various organosilanes were successfully prepared using a post-synthesis grafting method combined with a metal adsorption–reduction procedure. The correlation between catalyst structure, surface chemistry, metal loading, and catalytic activity was explored in the solvent-free selective oxidation of benzyl alcohol using molecular oxygen. TUD-1 outperformed other mesoporous silicas due to its unique open 3-D sponge-like mesostructure, which can effectively confine Pd nanoparticles and suppress the mass diffusion resistance. The type and content of grafted functional groups greatly affected the catalytic performance by tuning the surface basicity, metal particle size and size distribution, and metal–support interaction. 3-Aminopropyl triethoxysilane functionalization displayed the largest improvement in catalytic activity, showing a dramatically high quasi-turnover frequency of 18,571 h−1 for benzyl alcohol conversion.