Catalytic systems containing CaO substrate are considered as one of the most active catalysts. Egg shells contain a lot of calcium, which can be a rich source, inexpensive and accessible for calcium oxide production. In this research project, four new and recyclable functionalized nanoparticles based on calcium oxide were synthesized. The structure of prepared nanoparticles CaO @ SiO2 @ AIL, CaO @ SiO2 @ BAIL, CaO @ SiO2-SO3H and CaO @ SiO2-NH2-Sal-Zn was characterized using the analytical techniques such as FE-SEM, XRD, TGA, CHN, FT-IR And ICP-MS. The catalytic activity of these nanoparticles was investigated in the green synthesis of chromene, pyridine, pyrimidine and pyrazoline derivatives according to the following scheme. Some advantages of this work are the use of green conditions such as the use of water as solvent or non-solvent conditions, short reaction times, high yield of products and the use of egg shell as an available and inexpensive source for the preparation of catalysts, simple purification and reusability of catalysts. Keywords: Functionalized CaO nanoparticles, Green chemistry, Chromene, Pyridine, Pyrimidine, Pyrazoline. The synthesis of 2-imino-2H-chromenes and dihydropyrano[c]chromenes in the presence of CaO@SiO2@AIL nanocatalyst The synthesis of pyridines, pyrimidines, and pyrazolines in the presence of CaO@SiO2@BAIL nanocatalyst The synthesis of dihydropyrano[2,3‐c]pyrazoles and tetrahydrobenzo[b]pyrans in the presence of CaO@SiO2-SO3H nanocatalyst The synthesis of 4H-pyrans in the presence of CaO@SiO2-NH2-Sal-Zn nanocatalyst
