Magnetic Chiral Periodic Mesoporous Organosilica (PMO) Nanoreactors: Design, Preparation and Applications in Asymmetric Catalysis

Periodic mesoporous organosilica nanoparticles were synthesized in a sol-gel process under mild conditions. Their preparation was mediated by hydrolysis and condensation of bridged organo-alkoxysilane precursor compounds, (OR^{`</sup>)<sub>3</sub>Si-R-Si(OR<sup>`})₃, in the presence of a structure directing agent (SDA) which assisted the creation of uniform pores and structures. In our project, we succeeded to synthesize and characterize different chiral bridged-silane ligands that were utilized for the preparation of multiple chiral PMO NPs systems based on two major synthetic routes, either by co-polymerization or post-modification processes. The synthesis attempts were focused on the preparation of pure chiral PMO NPs that were composed merely of a chiral bridged organo-alkoxysilane monomer. The preparation of these systems was accomplished by applying different surfactants and ligands who could finally afford a monodispersed chiral PMO NPs consisted of 100% bridged-silane precursor. The obtained nanoparticles exhibited a very high surface area that reached up to 1699 m²g^-1. In addition, the major advancement in our research was the success – and for the first time- in preparing magnetic chiral PMO NPs. These nanoparticles were synthesized by a co-polymerization of 1,1`-((1R,2R)-1,2-diphenylethane-1,2-diyl)bis(3-(3-(triethoxysilyl)propyl)urea) chiral monomer by an o/w emulsion process, to give magnetic chiral PMO NPs with magnetite NPs in their cores. The obtained PMO nanoparticles exhibited a very high surface area that reached up to 1776 m²g^-1. The incorporation of these PMO NPs with metal NPs such as ruthenium, rhodium and palladium can afford a highly attractable system for many catalytic processes. The potential application of these nanoreactors was demonstrated in asymmetric transformations.