Green synthesis of α-Fe2O3 nanoparticles using Saussurea obvallata leaf extract and their catalytic application in chromene synthesis

Abstract

Green synthesis of α-Fe₂O₃ nanoparticles was successfully accomplished using Saussurea obvallata leaf extract through a sustainable plant-mediated approach. The synthesized nanoparticles were comprehensively characterized by FTIR, XRD, SEM, EDX, XPS, TEM, BET, UV–visible spectroscopy, TGA–DTA, DLS, and zeta potential analysis, revealing the predominant formation of crystalline rhombohedral α-Fe₂O₃ with a specific surface area of 29.42 m² g⁻¹ and an average crystallite size of 13.63 nm. The biosynthesized α-Fe₂O₃ nanoparticles exhibited excellent catalytic performance as a recyclable heterogeneous nanocatalyst for the multicomponent synthesis of chromene derivatives, affording product yields of up to 98% within 20 min at room temperature using 20 mg of catalyst in ethanol. The catalyst retained high activity over five consecutive reaction cycles, demonstrating excellent recyclability. Furthermore, post-reaction XRD analysis indicated that the characteristic crystalline structure of α-Fe₂O₃ remained largely unchanged after repeated use, confirming its structural stability under the applied reaction conditions. These findings demonstrate that plant-mediated α-Fe₂O₃ nanoparticles provide an efficient, environmentally benign, and sustainable catalytic system for the rapid synthesis of chromene derivatives.

Graphical abstract