Synthesis and characterization of ES/Cu(OH)2 nanocomposite: A novel and high effective catalyst in the green synthesis of pyrano[4,3-b]pyrans

The eggshell (ES) supported Cu(OH)2 nanoribbons containing 8 wt.% Cu2 + as a novel and heterogeneous catalyst was synthesized by simply adding an aqueous solution of CuSO4 on the eggshell support at ambient temperature. The nanocomposite system was characterized by scanning electron microscopy (SEM), transition electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and BET surface area analysis. Also, electrochemical impedance spectroscopy was used as powerful techniques for an electrical conductivity investigation. The loading of copper on the mesoporous supports provides high catalytic activity for the green synthesis of pyrano[4,3-b]pyrans. The reaction proceeds to completion in 5 min with excellent yields of 93–97%. The suggested strategy for synthesis of pyrano[4,3-b]pyrans is very interesting due to application of a green and low cost composite as a heterogeneous catalyst and its simplicity in preparation, short reaction time, high yields without further purification and high reusability without any loss of catalytic activity.