Synthesis of highly stable CoFe2O4 nanoparticles and their use as magnetically separable catalyst for Knoevenagel reaction in aqueous medium

Synthesis of spinel cobalt ferrite magnetic nanoparticles (MNPs) with average sizes in the range 40–50 nm has been achieved using a combined sonochemical and co-precipitation technique in aqueous medium without any surfactant or organic capping agent. The nanoparticules form stable dispersions in aqueous or alcoholic medium. The uncapped nanoparticles were utilized directly as a reusable catalyst for Knoevenagel reaction in aqueous ethanol (1:3). Compartmentation and recovery of the catalyst from reaction medium was done with the aid of an external magnet. High yield of corresponding Knoevenagel products were obtained within a very short time in presence of just 5 mol% of the catalyst at 50 °C.

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► CoFe2O4 nanoparticles synthesized without any surfactant or organic capping agent.
► Nanoparticles as well as its dispersion are quite stable.
► Nanoparticles can be used directly as a catalyst without any further modification.
► CoFe2O4 nanoparticles having basic character can catalyze Knoevenagel reaction.
► The nanocatalyst can be compartmented using an external magnet for reuse.