In this work, the magnetic Fe3O4 nanoparticles were encapsulated using a silica layer via a sol-gel method, which was labeled as SiO2@Fe3O4. Then, the surface of SiO2@Fe3O4 was modified using 3-iodopropyltrimethoxysilane (3-IPTMS), denoted as IPTMS@SiO2@Fe3O4. Also, 1-(1H-benzo[d]imidazol-2-yl)guanidine ligand (BimG) was synthesized from the condensation of cyanoguanidine and benzene-1,2-diamine in acidic conditions. Then, a new copper complex of BimG was anchored on the surface of IPTMS@SiO2@Fe3O4, which was labeled as Cu-BimG@SiO2@Fe3O4. This nanocatalyst was identified with TGA, BET, WDX, EDS, FTIR, XRD, SEM, AAS, and VSM techniques. Cu-BimG@SiO2@Fe3O4 was investigated as an effective, highly homoselective and returnable nanocatalyst for the synthesizing of tetrahydrobenzo[b]pyrans through a multicomponent reaction. The homoselectivity of this catalyst was confirmed by NMR spectroscopy. This Cu-BimG@SiO2@Fe3O4 catalyst showed good reusability for up to several runs without a meaningful loss of catalytic performance. The recovered Cu-BimG@SiO2@Fe3O4 nanocatalyst was characterized by SEM, EDS, WDX, and FTIR techniques, which were matched with a fresh catalyst.
