Homogeneous catalysts are dominant because they react in the same phase as the reactant. By nature, homogeneous catalysts are soluble in organic solvents, so that all catalytic sites are accessible and easy to tune by organic functional group inter-conversion. However, the solubility poses the main challenge in homogeneous catalysis; that is, to separate the catalyst from the desired product after the reaction. This limits the scope of homogeneous catalysis for some applications and is occasionally considered as a crucial drawback for product commercialization.
During the last two decades, great efforts have been devoted to developing alternatives to homogeneous catalysis in order to minimize separation costs and maximize product purity. Heterogeneous catalysis is the most obvious alternative, as it uses catalysts that are easy to separate and reuse. In addition, it can minimize the use of large quantities of environmentally toxic organic solvents that are needed for separation of the homogeneous catalysts and purification of the reaction products. Most heterogeneous catalysts are based on solid supports such as silica. Silica is highly stable, robust and easy to functionalize; thereby organic functional groups can be easily anchored by either covalent binding or surface adsorption in order to provide catalytic centers. Moreover, Superparamagnetic Iron Oxide Nanoparticles (SPION) have been one of the best choice of our research owing to their robustness, high surface area, and their distinct magnetic nature, rendering their separation from the heterogeneous reaction system virtually effortless. Surface functionalization of these solid supports with a novel design of chiral and achiral organic ligand and their subsequent appropriate metal complexes makes an excellent heterogeneous catalyst for the below applications :
- Regioselective organic transformation of substituted alkene to the corresponding aldehyde using syngas pressure.
- Enantioselective hydroformylation of olefins
- Coupling reactions such as Suzuki, Suzuki-Miyaura, Mizoroki-Heck reaction to produce higher aromatics
- Asymmetric hydrogenation of functionalized and unfunctionalized olefins.