NiCo2O4/g-C3N4: an efficient heterogeneous photocatalyst for visible-light-driven tandem synthesis of 2,3-disubstituted quinolines.

The development of sustainable photocatalytic platforms for heterocyclic scaffolds remains a central challenge in synthetic chemistry. In this work, we report the synthesis of a series of nanocomposites by loading 10, 20, and 30 wt% of nickel cobaltite (NiCo2O4) into graphitic carbon nitride (g-C3N4) nanosheets. Among these nanocomposites, 20 wt% NiCo2O4-loaded g-C3N4 achieves a yield of 82% over five recyclability cycles in the synthesis of 2,3-disubstituted quinolines. The composite was engineered by anchoring spinel NiCo2O4 nanoparticles onto two-dimensional g-C3N4 nanosheets synthesized via a hydrothermal method. Comprehensive characterization by XRD, FT-IR spectroscopy, XPS, FE-SEM, HR-TEM, UV-vis DRS, and PL spectroscopy collectively confirmed the heterostructure formation. The objective is to evaluate the photocatalytic activity of these catalysts for synthesizing 2,3-disubstituted quinolines under 12 W blue LED light. Scavenging experiments confirm the formation of radicals under light irradiation and provide crucial mechanistic insights. The methodology demonstrates broad substrate scope, requires mild reaction conditions, and allows the use of an earth-abundant, eco-friendly catalyst, offering a sustainable alternative to conventional metal-catalysed quinoline syntheses.