Flower-Shaped Ru-Doped ZnO Nanoparticles for Photocatalytic C–N Bond Formation under Visible Light

Although solar energy in pharmaceutical manufacturing poses challenges, its advantages in sustainability, cost-effectiveness, and innovation make it a promising area for further exploration. In this study, we report a rapid co-precipitation method for the synthesis of flower-shaped Ru-doped ZnO nanoparticles. The flower-like structures show an average particle size of ∼400 nm, accompanied by successful deposition of a substantial amount of Ru nanoparticles on their surfaces. The as-prepared Ru/ZnO nanoparticle photocatalyst was applied in a visible-light-driven photocatalytic protocol for the formation of carbon–nitrogen (C–N) bonds via the cross-coupling of aryl/heteroaryl carboxylic acids with N-heterocycles. This system is of particular interest to the pharmaceutical industry due to its potential utility in the synthesis of bioactive compounds. The flower-shaped Ru/ZnO nanoparticles were comprehensively characterized by using various analytical techniques, including X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM), Raman spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis, UV–visible spectroscopy, and inductively coupled plasma (ICP) analysis. The results confirm the successful synthesis of flower-shaped Ru/ZnO nanoparticles with a ruthenium loading of 3.12 wt %. The photocatalyst demonstrated excellent performance, achieving a conversion rate of 86% and a selectivity of 90% for the targeted cross-coupling reaction, and exhibited excellent photostability and recyclability under the reaction conditions. This efficient design, combined with a sustainable light source, highlights its potential for broader applications in industrial photocatalytic synthesis.