Catalytic Enhancement Through Interfacial Engineering: Ir-MoOx Nanocrystals on Silica for Nitroaromatic Hydrogenation

Abstract

The selective hydrogenation of halogenated nitroarenes into halogenated anilines poses a significant challenge due to the common issue of dehalogenation, which often results in low selectivity. In this research, we developed SiO₂-supported Ir-MoO_x nanostructures through the in situ transformation of IrMo/SiO₂. The Ir-MoO_x/SiO₂ catalyst we produced, with an optimal Ir/Mo molar ratio of 1:1, achieved a 95.1% conversion rate for p-chloronitrobenzene (p-CNB) and a 97.4% selectivity for p-chloroaniline (p-CAN), significantly outperforming the standalone Ir/SiO₂ catalyst. We explored how the MoO_x promoter affects the electronic properties of Ir particles and examined the impact of Ir-MoO_x interfaces on catalytic hydrogenation. This was done using advanced techniques, such as H₂ temperature-programmed reduction (H₂-TPR), H₂ temperature-programmed desorption (H₂-TPD), O₂ temperature-programmed oxidation (O₂-TPO), diffuse reflectance infrared Fourier transform spectroscopy, and kinetic analysis. The study revealed that the Ir-MoO_x interface plays a crucial role in facilitating H₂ dissociation and enhancing the adsorption of the reactants. Our Ir-MoO_x/SiO₂ catalyst showed excellent versatility across a wide range of substrates and maintained strong catalytic stability. This approach has the potential to be applied to other noble-metal-oxide systems for the efficient hydrogenation of halogenated nitroarenes.