An efficient Pd embedded 2D g-C3N4 photo catalyst intramolecular cyclization reaction for synthesis of quinolin-fused benzo[d] azeto[1,2-a] benzimidazole analogues

A highly efficient and facile synthesis method was developed to anchor ultra-small, monodisperse palladium nanoparticles (Pd NPs), with diameters of 40–50 nm, onto ultrathin crystalline 2D graphitic carbon nitride (g-C 3 N 4 ). The resulting Pd/g-C 3 N 4 nanocomposite synergistically combines the advantageous properties of the ultra-small Pd NPs and the ultrathin crystalline g-C 3 N 4 support. This catalyst demonstrated markedly enhanced photocatalytic performance for the synthesis of complex quinolin-fused benzo[d]azeto[1,2-a]benzimidazole analogues. The reaction proceeds via an intramolecular cyclization between o-phenylenediamine and various substituted 2-chloro-5-(2-methylquinoline-4-yl)benzaldehydes, involving simultaneous C–H/N–H and C–H/C–X bond activation. The photo catalyst was comprehensively characterized using SEM, TEM, EDS, XRD, BET, and FT-IR techniques. This work provides a promising and straightforward strategy for designing high-performance heterogeneous catalysts with well-dispersed metal active sites for advanced synthetic applications.