A simple and efficient protocol using palladium based lacunary phosphotungstate supported mesoporous silica towards hydrogenation of p-nitrophenol to p-aminophenol at room temperature

Abstract

A green and effective method is reported for the hydrogenation of p-nitrophenol to p-aminophenol using a Cs salt of Pd substituted keggin-type monolacunary phosphotungstate supported mesoporous silica (LPdW/MCM-41). A sample containing 50 wt% loading of the Pd substituted lacunary salt gave the best result towards the reaction, i.e. 99% conversion and 100% p-aminophenol selectivity. This economical and environmentally friendly method carried out at room temperature provides a potentially new approach for the synthesis of p-aminophenol from p-nitrophenol. In addition, the possibility to reuse the catalyst many times with great efficiency is another advantage. The catalyst was characterized by different techniques like X-ray diffraction, N₂ adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), phosphorous-31 NMR spectroscopy (³¹P NMR), Raman spectra and Fourier-Transform infrared spectroscopy (FT-IR). FT-IR studies confirmed the undegraded lacunary keggin structure of the salt supported on MCM-41.