Facile Combined Experimental and Computational Study: G-C₃N₄@PDMS-Assisted Knoevenagel Condensation Reaction under Phase Transfer Conditions

A new recyclable g-C₃N₄@PDMS heterogeneous catalyst has been developed as an efficient catalyst with an appreciable reactivity toward Knoevenagel condensation in the presence of crown ether (PTC). Here, a two-dimensional (2D) printed g-C₃N₄@PDMS heterogeneous catalyst opens the gate of possibility for high mechanical strength with the possibility of an appreciable recyclability. Various performed parameter studies clarify that g-C₃N₄ active sites exclusively enhance the cinnamic acid synthesis under mild reaction conditions. To explore the molecular mechanism of the condensation reaction over the heterogeneous catalyst surface, a systematic density functional theory-based computational study has been carried out. g-C₃N₄ material-based model substrate consisting of amine active sites has been considered for modeling the condensation reaction. The reaction energy profile for the condensation reaction between benzaldehyde and para-nitrotoluene on model substrate has been analyzed. The g-C₃N₄@PDMS catalyst is reused for several runs without loss in reaction rate, evidently due to the g-C₃N₄ active site being effectively implanted with highly resistant poly(dimethylsiloxane) (PDMS) layer. Recycled g-C₃N₄@PDMS heterogeneous 2D film characterization studies, viz., X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, confirm that the active site and molecular structure are well preserved even after multiple reaction cycles. Various reactants were screened using the heterogeneous g-C₃N₄@PDMS catalyst, exhibiting an appreciable product yield (∼99%) at room temperature in a short reaction time of 30 min.