(631c) Gold Nanoparticles Directly Deposited inside Mesoporous SBA-15 Zeolites As an Active and Thermal Stable Catalyst

The combination of zeolitic supports and metallic nanoparticles provides for unique catalysts which show high activities from the nanoparticles and high selectivities from the pore environment. However, nanoparticle synthesis inside of the pores of the zeolites is challenging due to the need for surface modification and chelating ligands. Herein, we present the use of Switchable Ionic Liquids (SIL) to synthesize gold nanoparticles outside of the pores of an SBA-15 zeolite and, by leveraging the switchable nature of the ionic liquid, deposit the gold nanoparticles inside of the pore environment. This method enables the preparation of highly active gold catalysts without the need for high temperature activation processes. The presence of gold nanoparticle inside the pore environment has been confirmed via TEM and the morphology of the nanoparticles is preserved through deposition. The average diameters of nanoparticles are 3.47±0.497 and 3.38±0.786 nm before and after deposition. The thermal stabilities of nanoparticles inside of the pore and onto non-porous environment were compared via the high temperature annealing studies. The nanoparticles deposited into an SBA-15 zeolite remained unchanged whereas nanoparticles similarly deposited onto non-porous silica grew significantly. The activity and selectivity of the catalysts are demonstrated via the oxidation of benzyl alcohol. All catalysts were active without any activation processes due to the use of the SIL. The SBA-15 and nonporous supports converted similar moles of benzyl alcohol over one hour, but the SBA-15 supported nanoparticles showed a higher selectivity towards benzaldehyde. Activities and selectivities were improved after vacuum oven treatment which leveraged the switchable nature of SIL. This work demonstrates the tunability of this method via low-temperature treatments to optimize the catalyst which is not possible via traditional methods. The optimum performance of the catalyst was achieved after 230 ^oC annealing whereas the nanoparticles deposited onto non-porous silica became catalytically inactive.