Hydrophobic effects on supported ionic liquid phase Pd nanoparticle hydrogenation catalysts.

Hybrid organosilicas prepared by sol-gel processes using 1-n-butyl-3-(3-trimethoxysilylpropyl)-imidazolium cations associated with hydrophilic and hydrophobic anions can be easily decorated with well dispersed and similar size (1.8-2.1 nm) Pd nanoparticles (Pd-NPs) by simple sputtering-deposition. Higher Pd concentration at the surface compared to the deeper region is obtained in the supports with smaller pore diameter (containing hydrophobic ILs) than in supports with the largest pore diameter (containing hydrophilic ILs). The IL hydrophobicity plays a central role in the hydrogenation of dienes by controlling the diene access to NP surface active sites.