Amine functionalized magnetic resorcinol formaldehyde as a green and reusable nanocatalyst for the Knoevenagel condensation

Herein, a novel amine-functionalized magnetic resorcinol-formaldehyde with a core-shell structure (Fe₃O₄@RF/Pr-NH₂) is prepared through the chemical immobilization of (3-aminopropyl)trimethoxysilane over Fe₃O₄@RF composite. Characterization through FT-IR, EDX, PXRD, and TGA confirmed successful surface modification while preserving the crystalline structure of Fe₃O₄. The VSM analysis demonstrated excellent superparamagnetic properties, and SEM and TEM images revealed spherical particles for the designed nanocatalyst. The Fe₃O₄@RF/Pr-NH₂ nanocomposite was employed as a robust nanocatalyst to promote the Knoevenagel condensation of benzaldehydes with ethyl cyanoacetate and malononitrile, resulting in the formation of substituted olefins. Various aromatic aldehydes were used as substrates in the presence of 0.01 g of Fe₃O₄@RF/Pr-NH₂, achieving high to excellent yields (87-97%) within short reaction times (10-50 min) in EtOH at 60 °C. The high performance of Fe₃O₄@RF/Pr-NH₂ is attributed to the hydrophobic nature of RF shell, which facilitates the accumulation of organic precursors around the catalytic active sites and enhances product yields. The designed magnetic catalyst could retain its high efficiency for at least ten runs. The metal-free, low-cost, and environmentally friendly attributes of the Fe₃O₄@RF/Pr-NH₂ catalyst make it a promising alternative to traditional metal-based catalysts.