High catalytic activity of supported Au nanoparticles assisted with the surface selective adsorption

Although the immobilization of gold nanoparticles (Au NPs) on the support is a conventional method for preventing them from aggregation and improving their separability at the cost of activity loss, herein, we developed a facile method to prepare supported Au NPs with the higher catalytic activity and better separability due to the selective adsorption of its functional surface. Firstly, the multi-functional carriers (amino-modified magnetic microspheres) were synthesized to immobilize Au NPs. Depending on its surface adsorption towards the reactant (p-nitrophenol), this carrier could greatly improve the mass transfer between p-nitrophenol (4-NP) and Au NPs resulting in the improvement of catalytic activity of supported Au NPs. The catalytic activity of supported Au NPs is increased more than 6.65 times compared with that of isolated Au NPs. Then, the effects of the particle size and supporting density of Au NPs on the catalytic activity were also investigated. Turnover frequency value of supported Au NPs (3.8 nm) reaches 16,000 h⁻¹ when its surface density is controlled to 2211 μg g⁻¹. Furthermore, the catalyst of Au/Fe₃O₄@PS-NH₂ showed excellent catalytic activity when various nitrobenzene derivatives were employed as substrates. Remarkably, these supported Au NPs could be easily isolated by magnetic separation in 30 s. This catalyst could be recycled for 45 times without any loss in catalytic activity. The high catalytic activity and easy separability of this supported Au NPs make it much potential in large-scale application.