Highly efficient CdS/CeO2/Ag3PO4 nanocomposite as novel heterogenous catalyst for Knoevenagel condensation and acetylation reactions

Abstract

In light of environmental and economic concerns, the use of heterogeneous catalysts that can function under gentler reaction conditions has recently become popular. In this study by using the precipitation method, CdS/CeO₂/Ag₃PO₄ ternary nanocomposites with varied molar proportions of CdS:CeO₂/Ag₃PO₄ were produced. The catalysts' surface functional groups; morphology and crystal structures were examined using FTIR, SEM-EDX and XRD respectively. The catalytic efficiency of all synthesized nanomaterials was tested on a model Knoevenagel condensation reaction. For the best catalyst, selected from the screening, the optimization of reaction conditions such as the solvent, catalyst load, concentration of reagents such as malononitrile/acetic anhydride, and temperature. The ternary nanocomposite CdS/CeO₂/Ag₃PO₄ (4:1) displayed higher catalytic activity (95.4 ± 3.2 %) than the rest of the nanomaterials prepared. Thus, the ternary nanocomposite CdS/CeO₂/Ag₃PO₄ with 4:1 mol ratio with optimized reaction conditions was used to check the substrate scope of Knoevenagel condensation and acetylation reaction. The synthesized Knoevenagel condensation and acetylation reaction products were also characterized by proton and carbon NMR for their structure determination. The nanocomposite's reusability was carried out and only 7.5 ± 2 % decrement was witnessed after four runs and 23.3 % after the fifth run. and this indicates the potential application of the catalyst to organic reactions. Furthermore, we have proposed the possible catalytic mechanisms for both organic reactions.

Keywords: Acetylation; Heterogeneous catalyst; Knoevenagel condensation; Nanocomposite.