Abstract
Iron oxide magnetic nanoparticles were synthesized with different sizes (11 and 30 nm). Subsequently they were shelled with a silica layer allowing grafting of an organic phosphine ligand that coordinated to the [MoI2(CO)3] organometallic core. The silica layer was prepared by the Stöber method using either mechanical (both 11 and 30 nm nanoparticles) or ultrasound (30 nm only) stirring. The latter nanoparticles once coated with silica were obtained with less aggregation, which was beneficial for the final material holding the organometallic moiety. The Mo loadings were found to be 0.20, 0.18, and 0.34 mmolMo·g−1 for MNP30-Si-phos-Mo,MNP11-Si-phos-Mo, and MNP30-Sius-phos-Mo, respectively, with the ligand-to-metal ratio reaching 4.6, 4.8, and 3.2, by the same order, confirming coordination of the Mo moieties to two phos ligands. Structural characterization obtained from powder X-ray diffraction (XRD), scanning electron microscopy (SEM)/ transmission electron microscopy (TEM) analysis, and Fourier-transform infrared (FTIR) spectroscopy data confirmed the successful synthesis of all nanomaterials. Olefin epoxidation of several substrates catalyzed by these organometallic nano-hybrid materials using tert-butyl hydroperoxide (tbhp) as oxidant, achieved very good results. Extensive testing of the catalysts showed that they are highly active, selective, recyclable, and efficient concerning oxidant consumption.
Highlights
Progressing our research on catalytic olefin epoxidation [17,18,19], we present in this work the synthesis and catalytic assessment of a series of catalysts based on a Mo complex tethered to the surface of silica-shelled magnetic iron oxide nanoparticles with different dimensions
MNP30 and MNP11 magnetic iron oxide nanoparticles with 30 and 11 nm diameter, respectively, were prepared by co-precipitation starting from a mixture of iron (II) and iron (III) chloride salts with ammonia, by a procedure described in the literature [20,21]
The particles were coated with a dense silica layer, adopting the Stöber method, using tetraethyl orthosilicate (TEOS) and ammonia as silica source and hydrolyzing agent generating MNP30 -Si and MNP11 -Si materials
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The development of nanosized chemical systems has become in recent years the focus of many research teams around the globe. The motivation to downsize chemical systems down to the nanoscale led to a huge increase in the edge knowledge concerning mastering the chemistry behind these systems alongside their applications. Bottom-up approaches have proved to be far more successful than the more classic topdown. The research arising from this topic yielded applications of nanoparticles in many fields, including sensing, energy, biomedicine, or catalysis, among others [1,2]
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