Magnetic Superhydrophobic Polymer Nanosphere Cage as a Framework for Miceller Catalysis in Biphasic Media

Abstract

This study demonstrated the use of a magnetic superhydrophobic polymer nanosphere cage derived from a Pickering emulsion as a framework for miceller catalysis in biphasic media. We designed this system through the covalent stabilisation of active site (2,2,6,6‐tetramethylpiperidine 1‐oxyl)‐grafted amphiphiles onto the magnetic hydrophobic core to form a micelle‐like architecture and used it as a Pickering emulsifier to develop a new kind of micelle‐catalysed biphasic system. The catalysis results reveal that these fixed micelle‐tethered 2,2,6,6‐tetramethylpiperidine 1‐oxyl catalysts demonstrate much higher activity than their soluble counterparts in the biphasic Montanari oxidation of alcohols, which could be due to the unique properties of Pickering emulsion and miceller catalysis. In addition, the excellent magnetic response ensures the efficient recycling of the catalyst by magnetic decantation. The catalyst can be recycled at least 10 times without significant loss of activity or degradation of magnetic susceptibility. Moreover, this study demonstrates that this new Pickering emulsion‐based and micelle‐catalysed biphasic system is technically simple and practically applicable.

Pickering Interfacial Catalysis for Biphasic Systems: From Emulsion Design to Green Reactions

“…Finally, in addition to POM systems, Zheng et al reported very recently magnetic amphiphilic polystyrene nanospheres with covalently tethered 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). [75] These catalysts showed a much higher activity than their soluble counterparts for the Montanari oxidation of a series of aromatic and aliphatic alcohols in w/o Pickering emulsions using NaClO as an oxidant (by a factor of 3). Furthermore, the catalysts could be efficiently recycled by magnetic decantation and reused for at least 10 times without significant loss of activity or degradation of magnetic susceptibility.…”

“…Finally, in addition to POM systems, Zheng et al. reported very recently magnetic amphiphilic polystyrene nanospheres with covalently tethered 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) 75. These catalysts showed a much higher activity than their soluble counterparts for the Montanari oxidation of a series of aromatic and aliphatic alcohols in w/o Pickering emulsions using NaClO as an oxidant (by a factor of 3).…”

Grenzflächenkatalyse in Pickering‐Zweiphasensystemen: vom Emulsionsdesign zu grünen Reaktionen

“…Außer den POM‐Systemen beschrieben Zheng et al. in einer neuen Arbeit magnetische amphiphile Polystyrolnanokugeln, an die 2,2,6,6‐Tetramethylpiperidin‐1‐oxyl (TEMPO) kovalent gebunden war 75. Diese Katalysatoren zeigten in der Montanari‐Oxidation von mehreren aromatischen und aliphatischen Alkoholen in Pickering‐Emulsionen mit NaClO als Oxidationsmittel eine weit höhere Aktivität (Faktor 3) als ihre löslichen Pendants.…”

A Green Strategy to Enhance a Liquid–Liquid Heterogeneous Reaction with a Magnetic Recyclable Pickering Emulsion

“…The catalysis results revealed that these fixed micelle-tethered TEMPO catalysts demonstrated a much higher activity than their soluble counterparts in the biphasic Montanari oxidation of alcohols, which could be due to the unique properties of Pickering emulsions and micellar catalysts. [14] However, the reason why catalyst-grafted nanoparticles can increase the reaction rate of the biphasic reaction system and how it enhances the reaction are still not clear. Little research has been performed to reveal the increase in activity of heterogeneous reactions contributed solely by the function of Pickering emulsion and how the surface properties contribute to the formation of such kind of emulsion.…”