Synthesis and characterization of carbon@HPW core/shell nanorod using potato as a novel precursor: Efficient catalyst for CN coupling reaction

Abstract

Carbon support with nanorod (CSN) structure was synthesized by natural potato as green and very cheap source via hydrothermal method. A novel type of core/shell nanorod catalyst was synthesized by the immobilization of 12-tungstophosphoric acid (HPW) on the surface of the CSN (C@HPW). Characterization of the core/shell nanorod catalyst was carried out using transmission electron microscopy (TEM), X-ray diffraction (XRD) pattern, energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FTIR) spectrophotometry, and Raman spectrophotometer. The TEM results show that morphology of carbon catalyst support could be changed from nanorod to core/sell nanorod by the immobilization of HPW. The characterization data derived from FTIR spectroscopy reveal that HPW on the support exists in the Keggin structure. The C@HPW core/shell nanorod was found to be a unique, effective, and eco-friendly catalyst for the CN coupling reactions for a broad range of aryl and alkyl amines and alcohols under aerobic conditions at room temperature. The excellent conversion at low reaction time shows that the catalyst has strong and sufficient sites, which are responsible for its catalytic performance. The acidity measurements of CSN and C@HPW by means of potentiometric titration with n-butylamine have been used to estimate their relative acid strength. Leaching of the HPW from the CSN was minimized by optimization of calcination temperature. The reused catalyst for at least five repeating cycles shows excellent activity. Keywords: Core/shell nanorod, 12-Tungstophosphoric acid, Natural potato, Carbon, CN coupling reaction