New monoclinic ruthenium dioxide with highly selective hydrogenation activity

Catalytic hydrogenation of aromatic compounds is an important industrial process, particularly for the production of many petrochemical and pharmaceutical derivatives. This reaction is mainly catalyzed by noble metals, but rarely by metal oxides. Here, we report the development of monoclinic hydrogen-bearing ruthenium dioxide with a nominal composition of H_xRuO₂ that can serve as a standalone catalyst for various hydrogenation reactions. The hydrogen-bearing oxide was synthesized through the water gas shift reaction of CO and H₂O in the presence of rutile RuO₂. The structure of H_xRuO₂ was determined by synchrotron X-ray diffraction and density functional theory (DFT) studies. Solid-state ¹H NMR and Raman studies suggest that this compound possesses two types of isolated interstitial protons. H_xRuO₂ is very active in hydrogenation of various arenes, including liquid organic hydrogen carriers, which are completely converted to the corresponding fully hydrogenated products under relatively mild conditions. In addition, high selectivities (>99%) were observed for the catalytic hydrogenation of functionalized nitroarenes to corresponding anilines. DFT simulations yield a small barrier for concerted proton transfer. The facile proton dynamics may be key in enabling selective hydrogenation reactions at relatively low temperature. Our findings inspire the search for hydrogen-containing metal oxides that could be employed as high-performance materials for catalysts, electrocatalysts, and fuel cells.