Flower-like TiO₂Nanostructures Coated with Fe₃O₄ Nanoparticles as Magnetic Ohmic Heterojunctions for the Photocatalytic Selective Oxidative Coupling of Primary Amines and Degradation of Tetracycline

Semiconductor-based photoredox catalysis is emerging as a green and promising strategy for solar–chemical energy conversion in organic synthesis and environmental treatment. Here, a hierarchical marigold-like magnetic Fe3O4/TiO2 composite was designed and prepared as an efficient and magnetically recyclable photocatalyst for selective oxidative coupling of primary amines and the degradation of tetracycline. Compared with its single-phase counterparts, the enhanced photocatalytic activity of composite can be assigned to its compositional and structural features. The formation of hierarchical Fe3O4/TiO2 Ohmic heterojunction can not only improve the light absorption and separation of photoinduced charge carriers but also provide more photoredox active sites. Furthermore, the Fe3+/Fe2+ cycle of Fe3O4 in the composite can facilitate the generation of reactive intermediates (•O2–) in the photocatalytic system, which can greatly promote photocatalytic performance. In addition, the magnetic Fe3O4/TiO2 heterojunction enables easy recycling by using an external magnet and demonstrates excellent reusability.