Recovery and reuse of expensive catalysts after catalytic reactions are important factors for sustainable process management. The aim of this Review is to highlight the progress in the formation and catalytic applications of magnetic nanoparticles and magnetic nanocomposites. Directed functionalization of the surfaces of nanosized magnetic materials is an elegant way to bridge the gap between heterogeneous and homogeneous catalysis. The introduction of magnetic nanoparticles in a variety of solid matrices allows the combination of well-known procedures for catalyst heterogenization with techniques for magnetic separation.
A catalyst generated from copper(I) oxide and 4,7-diphenyl-1,10-phenanthroline for the first time allows the catalytic protodecarboxylation even of deactivated aromatic carboxylic acids, giving rise to the corresponding arenes. Based on DFT calculations, a reaction pathway is proposed that accurately reflects the experimental results, such as the observed reactivity order of the substrates.
An organic−inorganic hybrid heterogeneous catalyst system was synthesized by covalently
anchoring oxodiperoxo molybdenum complexes [(L−L)MoO(O2)2] (L−L = (3-triethoxysilylpropyl)[3-(2-pyridyl)-1-pyrazolyl]acetamide) onto the mesoporous silica MCM-41 (Si−MCM-41) and aluminosilicate MCM-41 (Al−MCM-41) materials. Characterization of the functionalized materials by powder X-ray diffraction (XRD), N2 adsorption, and solid-state CP-MAS
NMR spectroscopy (13C and 29Si) demonstrates that the oxodiperoxo molybdenum complexes
are grafted successfully into the mesoporous MCM-41 materials. The structures of both the
mesoporous materials and the molybdenum complex are preserved during the grafting
process. All the hybrid materials are active and truly heterogeneous catalysts for the liquid-phase epoxidation of cyclooctene with tBuOOH as the oxygen source. The catalytic properties
(activity and recyclability) of the supported materials can be improved by their further
silylation using Me3SiCl, which can be explained by the increase of hydrophobicity of the
mesoporous surface due to removal of residual Si−OH groups. The modified aluminosilicate
MCM-41 materials show higher activities than the corresponding siliceous materials, which
might be due to the incorporation of Lewis acidic centers.
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