Silica-nanosphere-based organic-inorganic hybrid nanomaterials: synthesis, functionalization and applications in catalysis

The design and development of organic-inorganic hybrid nanomaterials and their applications in catalysis - an important area in sustainable chemistry - have captivated the attention of several researchers worldwide, as they enable environmentally friendly and benign catalytic processes. In recent years, novel approaches have been adopted to design highly selective nanostructured catalysts by controlling the interaction between the active catalytic species and the support material. There are extensive reports wherein silica nanoparticles (NPs) have been employed as solid supports for the fabrication of organic-inorganic hybrid nanocatalysts, possessing several outstanding features such as high activity and selectivity, excellent stability, efficient recovery and recyclability. Moreover, such quasi-homogeneous catalytic systems are free from diffusion problems that are generally associated with bulk catalytic systems, as these NPs can be dispersed in a wide range of organic solvents, eventually facilitating the accessibility of the substrates to the metal centres. This review attempts to summarise recent progress in the development of hybrid materials based on silica NPs, with special emphasis on the various fabrication strategies employed in previously published reports. Furthermore, a broad overview of the applications of these heterogeneous nanocatalysts in numerous organic transformations, including oxidation, reduction, condensation, amination, coupling, polymerization, addition and many more, is presented. It is believed that the successful applications of such versatile nanocatalytic systems would play a key role in establishing sustainable technologies.