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 Fe 3 O 4 /TiO 2 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 Fe 3 O 4 /TiO 2 Ohmic heterojunction can not only improve the light absorption and separation of photoinduced charge carriers but also provide more photoredox active sites. Furthermore, the Fe 3+ /Fe 2+ cycle of Fe 3 O 4 in the composite can facilitate the generation of reactive intermediates ( • O 2– ) in the photocatalytic system, which can greatly promote photocatalytic performance. In addition, the magnetic Fe 3 O 4 /TiO 2 heterojunction enables easy recycling by using an external magnet and demonstrates excellent reusability.