Unveiling the Synergistic Coupling Between Nickel Phosphide and Graphitic Carbon Nitride for Sustainable Catalytic Transfer Hydrogenation of Quinoline: Ensemble and Ligand Effects

Abstract

In recent years, metal phosphide catalysts have garnered immense attention among the catalysis community due to their facile synthesis and excellent catalytic activity but their promising potential in the field of organic transformation is not been fully explored. The synergistic coupling between the metal phosphide and the support material plays a crucial role in enhancing the overall catalytic activity as well as the recovery of the catalyst. Herein, this study reports nickel phosphide (Ni₂P) and graphitic carbon nitride (GCN) nanosheets as an interfacial catalyst for the effective and efficient transfer hydrogenation of quinoline. The significance of the developed interface between Ni₂P and GCN is revealed by the detailed spectroscopic and theoretical investigations, which enhances the dissociation of hydrogen source and the substrate interaction with the surface of the catalyst, thereby enhancing the selective transformation of quinoline to 1,2,3,4-tetrahydroquinoline. In the proposed transfer hydrogenation protocol for quinoline, formic acid is utilized as a bio-renewable hydrogen source, which serves as a potential replacement for molecular hydrogen. Further, detailed optimization studies are carried out to achieve good selectivity and product yield by varying reaction parameters. Therefore, using detailed mechanistic studies, the nickel phosphide supported on graphitic carbon nitride (Ni₂P-GCN) catalyst provides a promising reaction protocol for the transfer hydrogenation of quinoline.