Synthesis and characterization of Piperidine-4-carboxylic acid functionalized Fe3O4 nanoparticles as a magnetic catalyst for Knoevenagel reaction

Piperidine-4-carboxylic acid (PPCA) functionalized Fe3O4 nanoparticles as a novel organic–inorganic hybrid heterogeneous catalyst was fabricated and characterized by XRD, FT-IR, TGA, TEM and VSM techniques. Composition was determined as Fe3O4, while particles were observed to have spherical morphology. Size estimations using X-ray line profile fitting (10 nm), TEM (11 nm) and magnetization fitting (9 nm) agree well, revealing nearly single crystalline character of Fe3O4 nanoparticles. Magnetization measurements reveal that PPCA functionalized Fe3O4 NPs have superparamagnetic features, namely immeasurable coercivity and absence of saturation. Small coercivity is established at low temperatures. The catalytic activity of Fe3O4–PPCA was probed through one-pot synthesis of nitro alkenes through Knoevenagel reaction in CH2Cl2 at room temperature. The heterogeneous catalyst showed very high conversion rates (97%) and could be recovered easily and reused many times without significant loss of its catalytic activity.

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► Novel superparamagnetic Fe3O4–PPCA NPs were fabricated through one-pot reflux route.
► It could be reused several times without significant loss in catalytic activity for Knoevenagel rxn.
► No further modification of the Fe3O4–PPCA NPs is necessary for utilization as catalyst.