A Greener Approach for Synthesis of Magnetically Separable Fe ₃ O ₄ Nanoparticles for Friedel–Crafts Acylation and Synthesis of Quinoxaline: An Efficient Catalyst for Gas Sensing Applications

An ecologically friendly, low-cost, and biogenic preparation of iron oxide nanoparticles (Fe₃O₄ NPs) via a green approach utilizing waste biomass material is reported. The catalyst efficiency for Friedel-Crafts acylation to access functionalized anisole under solvent-free conditions and synthesis of quinoxaline derivatives utilizing water as a green solvent is described. The Fe₃O₄ NPs were synthesized biogenically using an aqueous extract of areca nut husk (ANH) and subsequently confirmed by various standard spectroscopic and microscopic characterization techniques. FESEM analysis displayed a spherical, agglomerated porous morphology, while the XRD analysis displayed a crystal size of 2.31 nm. TG-DT analysis revealed the stability of the Fe₃O₄ NPs to be good up to 450 °C, and XPS analysis indicated Fe²⁺ and Fe³⁺ oxidation states of the catalyst. A series of anisole and quinoxaline derivatives were prepared in moderate to high yields using the catalyst, and catalyst recyclability, mechanistic elucidation, and gram-scale synthesis are described herein. Additionally, the gas sensing proficiency of Fe₃O₄ NPs was examined toward oxidizing as well as reducing gases, establishing their potential for value-added applications.