In the present work, the novel CaO@walnut husk@ZnO nanoparticles were successfully synthesized by immobilization of Zn (II) on walnut husk extract-coated CaO nanoparticles using a simple and clean procedure. The structure and characterization of CaO@walnut husk@ZnO nanoparticles was properly investigated by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and thermogravimetric analysis techniques (TGA). Furthermore, some of benzylpyrazolylby coumarin derivatives as an important heterocyclic compounds were synthesized in good to high yields by using the related starting materials in the presence of the prepared CaO@walnut husk@ZnO nanoparticles as a high efficient catalyst. The structure of all synthesized products was well characterized by FT-IR, 1H- and 13C-NMR data. This clean procedure offers some advantages such as the use of a green and cheap biocatalyst (prepared from walnut husk waste and eggshells waste) short reaction times, simple workup and high yield of products.
