Nanoparticles of Ru on RuO2 from Pyrolysis of Ru-MOFs for Catalytic Hydrogenation

Abstract

The domain-limited catalyst, with its unique design of encapsulating active sites within nanoscale domains, significantly enhances catalytic efficiency and selectivity, while improving the stability and recyclability of the catalyst, which holds great significance for industrial applications. This paper presents a design strategy for a Ru-RuO₂/N–C domain-limited catalyst. This catalyst utilizes the porous structure of metal–organic frameworks (ZJU-100) to optimize the stability and selectivity of the ruthenium active site through spatial confinement effects. During the preparation process, the ruthenium complex (Ru(bpy)₃Cl₂·6H₂O) is first introduced in situ into the synthetic system of ZJU-100 (Zn-MOFs), followed by high-temperature pyrolysis of the precursor at 900 °C. In this process, the zinc metal nodes in the MOFs are reduced and evaporated, while the nitrogen from the ruthenium complex and the carbon from the MOFs framework confine the growth and distribution of ruthenium species, resulting in a uniform particle size distribution of 2–5 nm. The presence of Ru(0) and RuO₂ species in the catalyst is confirmed through XPS and HRTEM characterizations. This structural characteristic greatly promotes the selective hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Further studies reveal the reaction mechanism, finding that the formation of Ru–O bonds and the modulation of the oxidation state of ruthenium atoms play a crucial role in the catalytic activity of ruthenium catalysts. This provides an important theoretical foundation for designing efficient and stable ruthenium-based catalysts.