In the current research, much attention is paid to heterogenized nanostructure. Herein, we report the green synthesis magnetic nanoparticles (MNPs) of cobalt ferrite by the immobilization of erbium (Er) coated with folic acid (FA) which show effective catalytic properties and recyclability. Full characterizations with field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray atomic mapping, thermal gravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), inductively coupled plasmaoptical emission spectrometry (ICP-OES), and Fourier-transform infrared (FT-IR) spectroscopy techniques were undertaken to uncover structural properties of the prepared magnetic catalyst. The obtained nanohybrid complexes as efficient, recyclable, and green heterogeneous systems pave the way for producing pyrano[2,3-d]pyrimidinone and dihydropyrano[3,2-c]chromenes derivatives by the one-pot three-component condensation reaction of various aldehydes, malononitrile, and hydroxycoumarin or barbituric acid in green condition. This easily prepared organometalic catalyst presents many superiorities such as operational simplicity, high yield, short reaction time, utilization of commercially available or easily accessible starting materials, eco-friendly properties, and excellent purity. Most importantly, erbium-FA-coated CoFe2O4 can be easily separated and recycled from the reaction system using an external magnetic field. The magnetically recoverable biocatalyst can be recycled and reused six times while maintaining high activities. The activity of the magnetic catalyst can be maintained at more than 80% of that of the previous cycle. This research solves the recovery problem encountered in industrial applications of biocatalysts and presents a clean and green method for preparing pyrimidinones and chromenes
