Biowaste-Mediated Synthesis of CeO₂–TiO₂ Nanoparticles: An Efficient Recoverable Nanocatalyst for the Solvent-Free Synthesis of Antipyrine Derivatives and Their Biological Evaluation

A facile, efficient, and environmentally friendly protocol for the solvent-free synthesis of antipyrine- linked quinoline derivatives catalyzed by CeO₂–TiO₂ nanocatalyst under ultrasonication is developed. Antipyrine derivatives are involved in various synthetic processes and exhibit valuable biological activities, such as antibacterial, anti-inflammatory, antioxidant, and anticancer properties. Biowaste- derived CeO₂–TiO₂ nanoparticles have been synthesized using outer covering calyx leaves extract of Physalis peruviana fruits and utilized for the construction of biologically important antipyrine derivatives by the multicomponent reaction in short reaction time with excellent yield. The nanocatalyst was characterized by FT-IR, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electron dispersion spectroscopy (EDS). The functionalized nanoparticles show excellent reusability without any significant loss in catalytic activity. The hot filtering experiment shows that there is no noticeable leaching or boomerang effect and that the catalysis is heterogeneous in nature. All synthesized compounds underwent screening for antibacterial activity against selected microorganisms, and their antioxidant activity was assessed using DPPH (2,2-diphenyl-1-picrylhydrazyl). Some of the synthesized compounds exhibited promising results in both screenings.