“Click” Chemistry Assisted Synthesis of Magnetite‐CNT Nanohybrid Supported Gold Nanoparticles for Enhanced Catalytic Reduction of 4‐Nitrophenol

The magnetite (Fe3O4) nanoparticles were strategically tethered over carbon nanotube (CNT) templates by using UV light‐induced thiol‐yne “click” chemistry approach which was followed by immobilization of chitosan stabilized gold nanoparticles (Au NPs) onto this surface through electrostatic interactions. Their application as a magnetically recyclable catalyst was explored through the study of the model catalytic reaction of reduction of 4‐nitrophenol (4‐NP) in the presence of an excess of NaBH4. Kinetic studies on the reduction of 4‐nitrophenol revealed Au/Fe3O4−CNT ternary nanohybrids to serve as better catalytic systems compared to Au NPs. The catalytic reduction of 4‐NP was found to occur through the formation of active gold hydride (Au−H) species. The formation of Au−H species was facilitated by Au−Fe3O4 interaction through the transfer of hydride ions via dissociation of the B−H bond of the adsorbed borohydride ions [BH4]− and the heterolytic dissociation of molecular hydrogen (H2), produced on hydrolysis of NaBH4 on the surface of Au/Fe3O4. Moreover, the π–π interactions between the nitroaromatic ring of 4‐NP and the CNT surface are believed to facilitate their proximity. Further, on visible light irradiation, dissociation of H2 on the gold surfaces was enhanced by the localized surface plasmon resonance (LSPR)‐induced hot electrons. The scheme depicts enhanced catalytic reduction of 4‐nitrophenol on Au NPs supported on Fe3O4−CNT nanohybrid (Au/Fe3O4−CNT ternary nanohybrid) where gold‐hydride (Au−H) is regarded as active catalytic species.