(292e) Reversible Ionic Liquids (RevILs) for the Preparation of Thermally Stable SBA-15 Supported Gold Nanoparticle Catalysts

Reversible ionic liquids (RevILs) are ionic liquids that can be switched between molecular and ionic forms via two stimuli, and they can assist in the synthesis of colloidal gold nanoparticles. Herein, we demonstrate a facile catalyst synthesis technique that is able to deposit the RevIL-stabilized gold nanoparticles in the pores of SBA-15 mesoporous silica via incipient wetness technique without the functionalization of the SBA-15 surface. The location of nanoparticles inside the pores was confirmed by transmission electron microscopy technique. The RevIL technique is able to maintain the particle size (from 3.46 ± 0.53 nm to 3.28 ± 0.42 nm) after deposition. Under 230 ℃ calcination, the nanoparticles supported on the surface of the non-porous SiO₂ show an 183 % increase in the average diameter, whereas the nanoparticle inside the SBA-15 pores show only 11 % increase in the average diameter, indicating the improved thermal stability and additional confirmation of the location of nanoparticles inside the pores. The catalytic activity of prepared catalysts is assessed in the selective oxidation of benzyl alcohol and evaluated based on the surface turnover frequency (TOF_s) that has normalized the differences in the gold loading, surface area, and particle size. The porous SBA-15 supported gold catalysts (TOF_s = 26.4 s^-1) are extremely active in the selective oxidation of benzyl alcohol without high-temperature activation due to the absence of the ligands on the gold surface after deposition. Additionally, they are more active than the non-porous SiO₂ supported gold catalysts (TOF_s = 20.7 s^-1), indicating that the pore geometry enhances catalytic performance. Lastly, they are significantly more catalytically active than the traditionally prepared gold catalysts by an order of magnitude.