Rational design and fabrication of g-C₃N₄/CS/MOF-5 nanocomposite as a green, recyclable and efficient catalyst for the rapid synthesis of novel benzo[a]pyrano[2,3-c]phenazine derivatives

The efficient synthesis of high-yield organic compounds continues to represent a central challenge in the field of synthetic chemistry. In the present study, a novel nanocomposite (g-C₃N₄/CS/MOF-5) was rationally designed and synthesized to serve as a heterogeneous catalyst. Comprehensive characterization techniques, including SEM, EDS, elemental mapping, TGA, BET, FT-IR and XRD, were employed to elucidate the morphological, structural, compositional, thermal and surface characteristics of the prepared catalyst. The obtained results confirmed the successful preparation and structural integrity of the nanocomposite. Benefiting from the synergistic integration of g-C₃N₄, MOF-5, and chitosan, the catalyst demonstrated exceptional catalytic performance in the synthesis of benzo[a]pyrano[2,3-c]phenazine derivatives via a one-pot, four-component reaction involving thiobarbituric acid, o-phenylenediamine, benzaldehyde derivatives, and 2-hydroxy-1,4-naphthoquinone. The reactions were efficiently carried out in an ethanol-water (1:1) medium at 90 °C, affording the desired products in high yields (77-96%) within relatively short reaction times (30-120 min). Notably, the catalyst exhibited high surface area (15.84 m².g^-1) and excellent reusability, maintaining its catalytic activity over six consecutive cycles without appreciable loss in performance (96-89%).