Designing magnetic catalysts based on gold nanoparticles supported by ethylenediamine tetraacetic acid functionalized amino-modified poly(N-isopropyl acrylamide) for reduction of nitro compounds in water

A novel smart catalyst was developed with amino-modified thermo-responsive poly(N-isopropyl acrylamide) (PNIPAM) grafts on silica-coated magnetic nanoparticles using the conventional free radical polymerization process. By this methodology, the polymer was successfully grafted mainly onto silica-modified iron oxide nanoparticles (Fe₃O₄@Si). The PNIPAM-grafted Fe₃O₄@Si was then subjected to ethylenediamine treatment to produce the amino-functionalized support (Fe₃O₄@Si@PNIPAM-NH₂), which was subsequently modified with carboxyl functional groups by using EDTA (ethylenediaminetetraacetic acid) to create Fe₃O₄@Si@PNIPAM-NH₂-EDTA. Au nanoparticles were then decorated on this support through its two amines and four carboxylates. Different methods were used to study this novel catalyst, including inductively coupled plasma, Fourier transport infrared spectroscopy, TGA, dynamic light scattering, SEM, energy-dispersive X-ray analysis, vibrating sample magnetometry, XRD and elemental CHN analysis. The reduction of several aryl-nitro derivatives demonstrated a significant catalytic activity for the as-synthesized gold catalyst (Fe₃O₄@Si@PNIPAM-NH₂-EDTA-Au). The Au catalyst can be successfully removed from the reaction components using a magnetic field and used again in eight successive reduction reactions without significant gold leaching and loss of catalytic activity. © 2024 Society of Industrial Chemistry.