Organo-modified halloysite nanotubes as supports for gold nanoparticles as highly recyclable catalyst for hydrogenation of nitroarenes

Organo-modified halloysite nanotube (HNT) lumens were synthesized via an amine-silane-assisted method to encapsulate Au nanoparticles (Au-NPs) as catalysts for hydrogenation of nitroarenes. The obtained materials were characterized by attenuated total reflectance Fourier-transform infrared spectroscopy, zeta potential measurements, N₂ adsorption–desorption isotherms at −196 °C, X-ray diffraction, ultraviolet–visible diffuse reflectance spectroscopy, and transmission electron microscopy. The Au-NPs were uniformly distributed within the HNT lumen. An increase in Au loading (from 0.10 to 0.50 wt%) resulted in a broader Au-NPs size distribution. The catalysts were evaluated for nitrobenzene hydrogenation as test reaction under moderate reaction conditions (30 °C and 10 bar H₂ pressure in ethanol) to assess their performance and reusability. Results indicate that the catalysts are sensitive to variations in the Au-NPs size in the range of 1.5–6.5 nm. The catalyst containing 0.10 wt% Au exhibited exceptional stability and recyclability, retaining its catalytic activity with minimal loss over at least 10 consecutive reuse cycles. In addition, the best catalyst displayed a high efficiency and selectivity in the hydrogenation of pharmaceutical-based nitroarenes. The proposed organo-modified HNT material offers an innovative route for synthesizing efficient and reusable metal-based catalysts demonstrating significant potential for their use in another similar catalytic processes.