A recyclable heterogeneous nanocatalyst of copper-grafted natural asphalt sulfonate (NAS@Cu): characterization, synthesis and application in the Suzuki–Miyaura coupling reaction

Abstract

A new and efficient nanocatalyst was identified, synthesized and introduced and its catalytic activity was investigated in the Suzuki coupling reaction. This nanocatalyst can be synthesized by sulfonating natural asphalt as a high-carbon, cost-effective and accessible substrate using high-concentration sulfuric acid. After being neutralized by NaOH, it was transformed into sodium natural asphalt sulfonate (Na-NAS). Ultimately, the nanocatalyst was synthesized through a displacement reaction of sodium natural asphalt sulfonate with copper chloride. The solid derived (NAS@Cu) was identified using Transmission Electron Microscopy (TEM), Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscopy (SEM), N₂ sorption isotherms, Inductively Coupled Plasma (ICP), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Atomic Absorption Spectrometry (AAS) and Fourier-transform Infrared spectroscopy (FT-IR). NAS@Cu is a heterogeneous catalyst with advantages such as having a high specific surface area, being environmentally friendly and economically sound and simple purification and separation from the reaction mixture. Moreover, the nano-catalyst was recycled several times without any significant changes in its catalytic properties.