Homogeneous dispersion of Au nanoparticles into mesoporous SBA-15 exhibiting improved catalytic activity for nitroaromatic reduction

• Highly dispersive Au nanoparticles of different shapes are impregnated into SBA-15.
• Morphology of Au nanostructure was controlled by the amount of Au impregnation.
• Surface area and pore size notably changed after Au loading in mesoporous SBA-15.
• Au modified SBA-15 exhibits improved catalytic activity for nitrobenzene reduction.
• Selectivity of nitrobenzene reduction products depends on the m- and p-substitution.

Mesoporous silica SBA-15 having pore size (∼8 nm) was prepared using Pluronic P123 triblock copolymer followed by its surface modification with 2 wt.% of 3-aminopropyltriethoxysilane (APTES). The Au (1–10 wt.%) impregnation led to the formation of homogeneously dispersed Au nanospheres of size 5–6 nm, and nanorods of length 90–180 nm (and width 6–9 nm) throughout the APTES-modified SBA-15 without any distortion in the long range ordering of mesochannels. It was found that increasing amount (1–10 wt.%) of Au loading followed by calcination at 350 °C resulted in change of spherical morphology to rod like Au nanostructures beyond 5 wt.% loading. The surface area (664 m2/g) and pore volume (1.33 cm3/g) of bare SBA-15 were significantly reduced to 292 m2/g and 0.6031 cm3/g for Au nanosphere, and 457 m2/g and 0.7677 cm3/g for Au nanorod dispersed SBA-15, respectively, due to partial filling of mesopores. The catalytic activity of APTES-modified SBA-15 for the reduction of m- and p-dinitrobenzene is abruptly enhanced, after optimum amount (4–10 wt.%) of Au dispersion following a pseudo first order kinetic law that exhibited the best yield and 89% selectivity for m-phenylenediamine and 81% for p-nitroaniline formation, respectively.

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