Fe3O4 (iron oxide)-supported nanocatalysts: synthesis, characterization and applications in coupling reactions

The use of magnetic nanoparticles as a solid support material for the development of magnetically retrievable catalytic systems has led to a dramatic expansion of their potential applications as they enable environmentally-friendly and sustainable catalytic processes. These quasi-homogeneous catalysts possess numerous benefits such as ease of isolation and separation from the desired reaction mixtures using an external magnet and excellent recyclability. Consequently, much effort has been directed towards the synthesis of magnetically isolable nano-sized particles by developing methods such as co-precipitation, thermal decomposition, microemulsion, hydrothermal techniques etc. Further, in order to render them suitable for catalytic applications, several protection strategies such as surfactant/polymer, silica and carbon coating of magnetic nanoparticles or embedding them in a matrix/support have been reported in the literature. This review focuses on the substantial progress made in the fabrication of nanostructured catalysts with special emphasis on the protection and functionalization of the magnetite nanoparticles (Fe3O4). Finally, considering the importance of coupling chemistry in the field of organic synthesis, a broad overview of the applications of these magnetite nanoparticle-based catalysts in several types of coupling reactions has been presented. The future of catalysis lies in the rational design and development of novel, highly active and recyclable nanocomposite catalysts which would eventually pave the pathway for the establishment of green and sustainable technologies.