Green Synthesis of Copper Nanoparticles, Characterization and their Catalytic Application in the Synthesis of Dibenzoxazepine Khadijat .O. Abdulwahab 1 *, Timilehin Ogunyinka 1 , Sheriff.O. Kolade 1 and Luqman .A. Adams 1 Abstract In this research a green method was employed to synthesize copper nanoparticles by the reduction and precipitation of copper nanoparticles from copper sulphate solution using leave extracts of spinach and peppermint as capping and reducing agents while ascorbic acid acted as the anti-oxidant. The synthesized copper nanoparticles were then applied as catalyst in the synthesis of dibenzoxazepine from salicylaldehyde and aniline with a mixture of potassium carbonate, sodium bicarbonate and sodium carbonate as base in the presence of methanol. The synthesized nanoparticles were characterized by Fourier Transform Infra- Red spectroscopy (FTIR), powder X-ray diffraction (p-XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The IR spectra obtained indicated that the extracts were adsorbed (capped) on the surface of the copper nanoparticles through the functional groups present thereby preventing agglomeration. The p-XRD pattern were matched with those of cubic copper and this is also supported by EDS analysis which confirmed the presence of copper. The SEM images showed mostly spherical copper nanoparticles with an average size of about 10 μm. Finally, the FTIR spectrum showed the formation of a dibenzoxazepine using the copper nanoparticles via one pot approach. Keywords: green synthesis, copper nanoparticles, chemical reduction, room temperature Introduction In recent times, copper nanoparticles have found different applications due to their unique optical, catalytic, anti-microbial, mechanical and electrical properties. (Khodashenas and Ghorbani, 2014). Copper plays an important role in electronic circuits because of its excellent electrical conductivity. Copper nanoparticles have also been used as catalysts in organic reactions and is of high efficiency due to its high surface area. (Kaur et al.,2015) It is a good alternative for the noble metal catalysts such as silver and gold because of its high natural abundance, very conductive and more economical. Copper nanoparticles have been synthesized through different techniques including chemical reduction (Chandra and Kumar, 2016) electrochemical synthesis (Zhang and Hua, 2014), reverse micelles (Malik et al., 2012) microwave assisted synthesis (Tanghatari et al., 2017) thermal decomposition method (Kim et al., 2008) and green synthesis (Kulkarni and Kulkarni 2013). The chemical reduction method mostly involving reducing agents that provide electrons for the reduction of Cu salts (such as CuSO4, copper (II) acetylacetonate, CuCl 2, or Cu(NO3)2). Reducing agents used for this purpose often include cetyltrimethyl ammonium bromide (CTAB) (Wu and Chen., 2004), sodium borohydride (Dang et al 2011), hydrazine, (Saikova et al.,2010, Sierra-Ávila et al., 2014). Capping agents such as starch (Valodkar et al., 2011) chitosan (Usman et al., 2012) in chitosan was synthesized via the chemical reduction method 1. Department of Chemistry, Faculty of Science, University of Lagos, Nigeria *Corresponding Author Khadijat O. Abdulwahab 234-8096691294 kabdulwahab@unilag.edu.ng FRSCS Vol.1 No. 3 Official Journal of Dept. of Applied Chemistry, Federal University of Dutsin-Ma, Katsina State. http://journal.fudutsinma.e du.ng/index.php/rcs/index ISSN: 2705-2354 Print 2705-2362 Electronic Accepted: 17 th Dec, 2019 Published: 31 th Dec, 2019 45