Hollow Magnetic Mesoporous Nano-catalyst Preparation And Its Application In Organic Reactions

Hollow magnetic mesoporous silica spheres (HMMS) with well-defined structures have received great interest as supports in heterogeneous catalysis systems, owing to their unique properties such as low toxicity, good compatibilities, low density, magnetic properties and very high specific surface area with abundant Si-OH bonds on the pore surface. Obviously, to combine metal nanoparticles and HMMS to form hollow magnetic mesoporous nano-catalysts (metal/HMMS) will realize high activity and magnetic recyclability. We synthesized Pd/HMMS and Ag/HMMS, to analyze the structure of the catalysts through a variety of characterization methods, and study their application in organic reactions.1. The nano-catalyst of hollow magnetic mesoporous silica spheres (Pd/HMMS), with Pd and Fe3O4nanoparticles embedded in the mesoporous silica shell, were successfully prepared by using the colloidal carbon spheres of glucose, Pd and Fe3O4heteroaggregates as the hard template together with a coating of tetraethoxysilane (TEOS) and cetyltrimethylammonium bromide (CTAB) mixture. The synthesized Pd/HMMS shows excellent catalytic activity in the Suzuki cross-coupling reaction of iodobenzene with phenylboronic acid with over99%yield in3min and can be recycled multiple times without any significant loss in catalytic activity.2. A nano-cayalyst (Ag/HMMS) composed of hollow magnetic mesoporous spheres (HMMS) and Ag nanoparticles was found to be an efficient catalyst for synthesis of P-enamino ketones or esters from β-dicarbonyl compound under mild reaction conditions. Using methanol as a solvent, the condensation reaction of acetylacetone and benzylamine proceeded to give over100%yields at60℃for1h. The novel catalyst could be easily recovered by an external magnet from the reaction mixture and recycled five times without any significant loss in activity.