OICC Press Iranian Journal of Catalysis 2345-4865 8 3 2024 02 03 Graphene–ZnO@SiO2 hybrid: An efficient and solid acid catalyst for synthesis of azlactones under ultrasound irradiation EN Sodeh Sadjadi Material and Nuclear Fuel School, Nuclear Science and Technology Research Institute, End of North Karegar Ave. P.O. Box: 14399-51113, Tehran, Iran. Journal Article 2024 02 03 The central theme of this article is how to explore a novel route to fabricate graphene– ZnO@SiO2 hybrid by a covalent process. The synthesis procedure consists of three-steps: (1) synthesis of ZnO nanoparticles, (2) ZnO nanoparticles modification by tetraethyl orthosilicate and (3-aminopropyl) triethoxysilane after introduction of amino groups on its surface, (3) the covalent attachment of ZnO@SiO2 onto the graphene surface by the amidation reaction between amino group of ZnO@SiO2 and carboxylic group of graphene. This hybrid was then used as a catalyst for the synthesis of azlactones obtained by Erlenmeyer synthesis from aromatic aldehydes and hippuric acid under the ultrasonic irradiation. The protocol offers advantages in terms of higher yields, short reaction times, mild reaction conditions, and reusability of the catalyst.