Structural Regulation of Magnetic Polymer Microsphere@Ionic Liquids with an Intermediate Protective Layer and Application as Core–Shell–Shell Catalysts with High Stability and Activity

Abstract

A novel ionic liquid immobilized on a magnetic polymer microsphere catalyst is reported in this paper. The obtained core–shell–shell catalyst consisted of magnetic nanoparticles (MNPs) as the core, catalytic inert St-co-DVB as the intermediate protective layer, and cross-linked polyaryl imidazole ionic liquids as the active catalytic layer located at the outermost [Im[OH]/MNPs@P(St-DVB)@P(VBC-DVB)]. This catalyst exhibited a high ion-exchange rate (64.65%), high saturation magnetic strength, and excellent acid and alkali corrosion resistance. In the catalyzed Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate, the conversion of benzaldehyde maintained at 92.1% during six times reuse. Optimizing the materials of the protective layer and regulating the thickness of the inert protective layer decreased the corrosion ratio of MNPs in acidic media from 44.82 to 0.44%. Adjusting the thickness of the catalytic layer realized excellent catalytic activity (97%) and high magnetic response performance. In summary, introducing an inert protective layer to the structure of ionic liquids immobilized on the magnetic polymer microsphere catalyst, regulating its thickness, and optimizing its structure achieved a catalyst with high activity, excellent stability, and easy magnetic separation.

Synthesis of ZnFe2O4@MoS2 core-shell nanocomposites with enhanced lubrication performance as lubricant additives

“…Core–shell composites have attracted widespread attention because of their unique structural advantages (Huang et al , 2019; Ren et al , 2020; Xu et al , 2018; Li et al , 2012; Lin et al , 2015; Ma et al , 2021). Hard core particles can provide better support for the soft shell, so that the shell can continuously repair deep wear marks to reduce matrix wear; at the same time, the characteristics of low shear force of soft shell can extend the rolling lubrication effect time of core particles and reduce the abrasive wear caused by core particles to the matrix; duplex composite particles form rolling elements by desorption at the friction interface, which promotes the uniformity and integrity of the transfer film and improves the self-healing ability of the transfer film (Chen et al , 2020a). In addition, the interaction of core–shell interface can provide an important basis for the controllable preparation of core–shell composites and the formation of core–shell complexes with stable structure and easy to uniformly disperse, and the core size and shell thickness can be regulated by changing the reagent ratio (Wang et al , 2022; Li et al , 2022; Chen et al , 2023).…”

l-Asparagine–EDTA–amide silica-coated MNPs: a highly efficient and nano-ordered multifunctional core–shell organocatalyst for green synthesis of 3,4-dihydropyrimidin-2(1H)-one compounds

“…29 Therefore, MNPs must be stabilized to improve their properties and prevent undesirable agglomeration. 30,31 In fact, they are coated with a protective layer such as carbon layers, 32,33 organic polymers 34 or silica. [35][36][37] Moreover, multi-component reactions (MCRs) are the most desirable powerful synthetic route in which three or more reactants come together in a single reaction vessel to form a wide range of acyclic or heterocyclic compounds by one-pot processes.…”

“…29 Therefore, MNPs must be stabilized to improve their properties and prevent undesirable agglomeration. 30,31 In fact, they are coated with a protective layer such as carbon layers, 32,33 organic polymers 34 or silica. 35–37…”

L-(+)-Tryptophan methyl ester derived polymeric microbeads as an efficient heterogeneous catalyst for green synthesis of 2-amino-4-(nitromethyl)-4H-chromene-3- carbonitriles

“…For example, cinchonidinium salts of core-corona polymer microspheres were applied several times in asymmetric alkylations without loss of the enantioselectivity [ 12 ]. Shi and coworkers reported the synthesis and characterization of a polymer microsphere catalyst [ 13 ]. Ionic liquid immobilized catalyst was applied in the Knoevenagel condensation of ethyl cyanoacetate and benzaldehyde.…”