Preparation and catalytic application of sulfonated polyvinyl alcohol-Al-pillared α-zirconium phosphate (SPV-AZP) hybrid material towards synthesis of 4,6-diarylpyrimidin-2(1H)-ones

Abstract

In this study, a series of new hybrid catalysts were prepared by dispersing sulfonated polyvinyl alcohol (SPVA) in the porous matrix of Al-pillared α-zirconium phosphate. Initially, the α-zirconium phosphate (ZP) was prepared by reflux method, which was subsequently intercalated with [Al13O4(OH)24(H2O)12]7+ cationic clusters to prepare Al-pillared α-zirconium phosphate (AZP). A significant improvement in interlayer space, surface area and porosity of the parent zirconium phosphate was noticed due to bilayer intercalation of Al137+ species into the interlayer region. The ZP and AZP materials were used as host lattice for dispersion of sulfonated polyvinyl alcohol. The obtained hybrid materials were characterized using XRD, FESEM, HRTEM, TGA-DTA, FTIR, UV–Vis, TPD and XPS analytical techniques. The polymeric species were decorated as crystalline nanoparticles in the periphery of ZP particles, whereas they occurred in a well dispersed in the AZP lattice. TPD study revealed a significant improvement in the number of medium and strong acidic sites after dispersion of the SPVA polymer in the AZP matrix. The hybrid materials were used as efficient heterogeneous catalysts for multicomponent one pot synthesis of 4,6-diarylpyrimidin-2(1H)-ones by condensation of aryl aldehydes, ketones and urea using ethanol as solvent. Structurally diverse diarylpyrimidinones were synthesized in high yield and purity in a short span of time. The enhanced catalytic activity of the hybrid material has been ascribed to the well dispersion of the polymeric species and improved accessibility of the acidic sites due to expanded interlayer space of AZP material.