Mesoporous Silica (MCM-41) Containing Dispersed Palladium Nanoparticles as Catalyst for Dehydrogenation, Methanolysis, and Reduction Reactions

Generating highly dispersed metal NPs of the desired size on surfaces such as porous silica is challenging due to wettability issues. Here, we report highly active and well-dispersed Pd incorporated mesoporous MCM-41 (Pd@MCM) using a facile impregnation via a molecular approach based on hydrogen bonding interaction of a palladium beta-diketone complex with surface silanol groups of mesoporous silica. Controlled thermal treatment of so obtained materials in air, argon, and hydrogen provided the catalysts characterized by electron microscopy, nitrogen physisorption, X-ray diffraction and spectroscopy. Gratifyingly, our catalyst provided the lowest ever activation energy (14.3 kJ/mol) reported in literature for dehydrogenation of NaBH4. Moreover, the rate constant (7x10-3 s-1) for the reduction of 4-nitrophenol outperformed the activity of commercial Pd/C (4x10-3 s-1) and Pd/Al2O3 (5x10-3 s-1) catalysts. Supported catalysts: Air-calcination of a silica supported palladium complex provides more active catalyst for dehydrogenation and reduction reactions compared to those obtained by its pyrolysis under hydrogen or argon atmosphere.image