Catalytic Enhancement Through Interfacial Engineering: Ir-MoO_<i>x</i> Nanocrystals on Silica for Nitroaromatic Hydrogenation

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-MoOx nanostructures through the in situ transformation of IrMo/SiO2. The Ir-MoOx/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 MoOx promoter affects the electronic properties of Ir particles and examined the impact of Ir-MoOx 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-MoOx interface plays a crucial role in facilitating H2 dissociation and enhancing the adsorption of the reactants. Our Ir-MoOx/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.