In this research project, an environmentally friendly solid catalyst was synthesized from low-cost rice husk (RH–SiO 2 ). Then, RH–SiO 2 was applied to support cobalt ferrite (CoFe 2 O 4 ) on the surface or in- side the pores of amorphous SiO 2 . The nanoparticles were later modified by sulfonated (CoFe 2 O 4 @RH- Pr-SO 3 H) through modification with 3-mercaptopropyltrimethoxysilane (MPTMS) and subsequent oxida- tion with hydrogen peroxide (H 2 O 2 ). The characterization techniques including FT-IR, BET, CHNS, FE-SEM, TEM, VSM, TGA-DTG, EDX and X-ray mapping confirm the structure of this supported complex. Further- more, the effect of the preparation method of the catalyst CoFe 2 O 4 @RH-Pr-SO 3 H was extensively studied against the synthesis of 3,4-dihydropyrimidinones and octahydroquinazolinones. There are no harmful or- ganic solvents used in the current approach. The nontoxic nature, short reaction times, easy recovery and efficient reusability of the CoFe 2 O 4 @RH-Pr-SO 3 H are advantages of this approach. The nanocatalyst could be recovered easily and reused several times without the loss of its activity.
