Surface Deposition of Magnesium Ferrite-Based Supports with Bimetallic Gold/Silver Nanoparticles for the Catalytic Reduction of Nitroaromatics.

Surface deposition of magnesium ferrite nanoparticles (MgFe 2 O 4 NPs) with bimetallic gold/silver (Au/Ag) nanoparticles was conducted using the seed-mediated growth method to obtain magnetic-metallic composite catalysts for use in the catalytic reduction of nitroaromatics. Two types of amine-functionalized MgFe 2 O 4 and MgFe 2 O 4 @SiO 2 NPs were used as magnetic supports for the surface deposition process. The combination of several characterization analyses (i.e., XRD, XPS, TEM, SEM, EDS, and VSM) confirmed the successful syntheses of the MgFe 2 O 4 /Au/Ag and MgFe 2 O 4 @SiO 2 /Au/Ag NPs. The catalytic reduction of 4-nitrophenol using sodium borohydride as a reducing agent revealed that the reaction was completed within 2 min by using MgFe 2 O 4 /Au/Ag and MgFe 2 O 4 @SiO 2 /Au/Ag NPs as catalysts. The appearance rate constant of the MgFe 2 O 4 /Au/Ag NPs was slightly higher than that of the MgFe 2 O 4 @SiO 2 /Au/Ag NPs. In terms of reusability, high conversion (>80%) of the reduction of 4-nitrophenol was still obtained after 7 and 10 consecutive cycles for the MgFe 2 O 4 /Au/Ag and MgFe 2 O 4 @SiO 2 /Au/Ag catalysts, respectively. Interestingly, these two catalysts exhibited the highly catalytic conversion of the chosen nitroaromatic derivatives (i.e., 4-nitrobenzaldehyde and 4-nitroaniline). On the whole, the MgFe 2 O 4 /Au/Ag and MgFe 2 O 4 @SiO 2 /Au/Ag NPs could be utilized as suitable and sustainable catalysts for the catalytic reduction of nitroaromatics due to several desirable features (i.e., high activity, facile and rapid separation by a magnet, and good reusability).