N-Doped Carbon Wrapped Polyoxometalate Derived from POM-IL Hybrid: A Heterogeneous Catalyst for the Synthesis of Coumarin Derivatives under Solvent-Free Conditions

Article abstract of DOI:10.1002/ejic.201900010

Vanadium substituted Keggin type polyoxometalate loaded N-doped carbon was prepared from polyoxometalate ionic liquid hybrid by carbonization process. The decomposition of organic part generates various functional groups leaving polyoxometalate part intact. The catalyst was characterized by elemental analysis, FTIR, MAS ¹³C NMR, XPS and electron microscopy studies. The presence of carboxylic acids, aromatic and hetero-aromatic groups in the catalyst was confirmed by ¹³C NMR. The high resolution C1s and O1s XPS analysis further confirmed the presence of these groups. Various oxidation states of nitrogen were confirmed by deconvoluted N1s XPS spectra. Pyridine adsorption study confirms the presence of Bronsted and Lewis acid sites in the catalyst. Layered structure of the catalyst was confirmed by HR TEM analysis. The hybrid material displayed excellent catalytic activity towards the synthesis of coumarin derivatives under solvent-free conditions.