Fabrication of Ir-CoOx@mesoporous SiO₂ Nanoreactors for Selective Hydrogenation of Substituted Nitroaromatics

Nanosized Ir catalysts suffer from serious side reactions and poor stability during hydrogenation of substituted nitroaromatics to produce aromatic amines. In this work, core–shell nanostructures with sub-4 nm Ir-CoO x hybrid cores and mesoporous SiO 2 shells were designed and prepared to overcome these problems. The Ir-CoO x hybrid cores were converted from IrCo alloy nanoparticles (NPs) inside SiO 2 through in situ calcination and reduction pretreatments. The SiO 2 mesoporous shells in Ir-CoO x @SiO 2 nanoreactors prevented the agglomeration/sintering of IrCo NPs, while allowing the free reactants and products (big molecules). The synergy between Ir and CoO x species improved H 2 adsorption, thus affecting the reaction rate as well as the selectivity to aromatic amines. As a result, the obtained Ir-CoO x @SiO 2 nanocatalyst showed tremendous improvement in catalytic activity, selectivity, and stability.