Carbon nanotube-supported gold nanoparticles as efficient catalyst for the selective hydrogenation of nitroaromatic derivatives to anilines

Gold nanoparticles (AuNPs) with sizes between 3 and 10 nm were firmly supported on pristine multi-walled carbon nanotubes (MWCNT) in high yields by a facile linker-free deposition route using aqueous suspensions of pre-reduced gold precursors. For the first time, the resulting AuNP-MWCNT hybrid material was employed as catalyst for the hydrogenation of a series of substituted nitroarenes under mild reaction conditions. High catalytic activity with turnover frequencies (TOF) values up to 1200 h−1 were achieved accompanied by a remarkable chemoselectivity. Recyclability tests did neither reveal leaching nor changes in size or oxidation states of the AuNPs. The concomitant presence of Au0 and AuI accounts for both the superior catalytic performance and the high stability of the hybrid material. Preferential orientation of nitroarenes on the MWCNT surface due to π–π interactions coupled with coulombic contact of the nitro group to the AuNPs most likely explains the high chemoselectivity of the hybrid material, and further underlines the valuable role of MWCNTs for catalytic reactions.