A facile synthesis of clay - graphene oxide nanocomposite catalysts for solvent free multicomponent Biginelli reaction

In the present study, clay - graphene oxide nanocomposite catalysts were successfully used for the first time in the multicomponent one pot organic synthesis. The facile development of the hybrid clay - graphene oxide nanocomposite has been achieved by a cost-effective method without the use of any surfactants. The partial reduction of graphene oxide, upon incorporation of clay layers and subsequent heat treatment, is evident from the X-ray diffraction patterns and FTIR spectra of the samples. X-ray photoelectron spectroscopy as well as Al-27 and Si-29 NMR spectral analyses provided useful information regarding the interaction between clay layers and graphene oxide through Si-O-C and Al-O-C bonding. The deconvoluted XPS spectrum of O (1s), Al (2p) and Si (2p) indicates the increased availability of acidic functionalities in the hybrid nanocomposite. FESEM and TEM photographs show the random distribution of the clay nano-flakes over the graphene oxide sheets and this may be the reason for the availability of more of the active sites for catalysis. Synthesis of 3,4-dihydropyrimidinones by the one pot Biginelli reaction was done over the present clay - graphene oxide heterogeneous catalysts with high product yield. Short time period of reaction and excellent reusability up to 8 repeated cycles under solvent free conditions are the key advantages of the present highly active hybrid nanocomposite clay - graphene oxide catalysts over most of the other reported catalysts used for Biginelli reaction. (C) 2017 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University.