Metal-free, biomass-derived nano-architectured carbon quantum dots as an efficient acid-base bifunctional catalyst for facile synthesis of benzo[g]chromene and pyrimidine analogs

Abstract

Perusal of literature reports revealed that variedly functionalized carbon quantum dots (CQDs) have been extensively studied as sustainable alternative to conventional nanomaterials in catalysis. In this context, herein, we have designed and developed an efficient, metal free, green and heterogeneous sulfonic acid functionalized carbon quantum dots (CQDs)-based catalyst derived from biomass for one pot multicomponent reactions. The developed catalyst has been fully characterized using various techniques such as DLS, IR spectroscopy and zeta potential measurements. The synthesized catalyst acts as a bipolar catalyst which can activate all the three components via hydrogen bond donor as well as hydrogen bond acceptor sites in the reaction mixture, to synthesize pyrimidine and 4H-benzo[g]chromene derivatives in pure aqueous medium. Further, the catalyst exhibits significant reusability up to six cycles without any significant loss in its catalytic activity. Therefore, an economical and sustainable protocol has been developed for facile syntheses of biologically important heterocycles through an efficient and easily recoverable biomass derived catalyst in pure aqueous medium. Apparently, the developed strategy provides good eco-scale and E-factor values, which are acceptable according to green chemistry protocols.