Core-Double-Shell Fe₃O₄@Carbon@Poly(In^III-carboxylate) Microspheres: Cycloaddition of CO₂ and Epoxides on Coordination Polymer Shells Constituted by Imidazolium-Derived Al^III–Salen Bifunctional Catalysts

Abstract

A hydrid microsphere Fe3O4@carbon@poly(In(III)-carboxylate) consisting of a cluster of Fe3O4 nanoparticles as the core, a carbon layer as the inner shell and a porous In(III)-carboxylate coordination polymer as the outer shell was prepared and applied as a recyclable catalyst for the cycloaddition reaction of CO2 and epoxides. Construction of this hybrid microsphere was achieved in the two steps, including (1) the one-pot solvothermal synthesis of Fe3O4@C particles with the abundant carboxylic groups on the carbon surface and (2) the subsequent growth of the outer shell polymers based on the precipitation coordination polymerization. Imidazolium-substituted Salen ligands were synthesized and chelated with the In(III) ions using the terminal carboxylic groups. The coordination polymer shell was formed on the Fe3O4@C particles, and the structures including shell thickness, surface area and porosity could be varied by tuning the feeding ratios of the In(III) ions and the ligands. The optimal structure of the coordination polymers showed a shell thickness of ca. 45 nm with ∼5 nm of mesopore, 174.7 m(2)/g of surface area and 0.2175 cm(3)/g of pore volume. In light of gas uptake capability, catalytic activity and magnetic susceptibility, cycloaddition of CO2 with a series of epoxides were studied by using Al-complexed Fe3O4@C@In(III)-[IL-Salen] microspheres. The results validated that the self-supporting catalytic layer with high surface area was of remarkable advantages, which were attributed from great increment of effective active sites and combination of nucleophilic/electrophilic synergistic property and CO2 uptake capability. Therefore, these hybrid microspheres provided excellent catalytic activity, prominent selectivity to cyclic carbonates and outstanding recyclability with the assistance of an applied magnetic field.

Dipolar‐Distribution Cavity γ‐Fe2O3@C@α‐MnO2 Nanospindle with Broadened Microwave Absorption Bandwidth by Chemically Etching

“…It is known that γ‐Fe 2 O 3 guarantees morphology versatility and chemical stability compared to those of magnetite . So far, iron oxide@C core–shell with various shapes, including rod, ring, sphere, and dendrite, has been fabricated and used in the fields of catalyst, electrochemistry and microwave absorption . For example, Lu and co‐workers synthesized polypyrrole‐coated Fe 2 O 3 @C multifunctional composites .…”

Ionic Polymer Microspheres Bearing a CoIII–Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO2 and Epoxides

“…[27,28] Manyr esearchers have demonstrated OICs that contain aL ewis acidic metal centera nd an ucleophilic halogen anion (X À )p ortiona sh ighly efficient bifunctionalc atalysts for the coupling reactionb e-tweenC O 2 and epoxides under co-catalyst free conditions owingt ot he cooperative effects of the catalytic functional groups. [29][30][31] For example, Ema et al synthesized Mg-porphyrin bifunctional catalysts functionalized with quaternary ammonium groups, which showed high catalytic activity for the solvent-free and co-catalyst free synthesis of cyclic carbonates from CO 2 and epoxides. [32] Ji et al prepared as eries of polyether-based imidazolium IL-modifiedm ononuclear salen-Al complexes and used them as highly efficientc atalysts for the CO 2 cycloaddition reaction.…”

“…Recently, organometallic ionic complexes (OICs) have emerged as very attractive catalysts because they can be made from readily available and highly tailorable metal and ligand precursors for multifunctional integration . Many researchers have demonstrated OICs that contain a Lewis acidic metal center and a nucleophilic halogen anion (X − ) portion as highly efficient bifunctional catalysts for the coupling reaction between CO 2 and epoxides under co‐catalyst free conditions owing to the cooperative effects of the catalytic functional groups . For example, Ema et al.…”

Cobalt–Salen-Based Porous Ionic Polymer: The Role of Valence on Cooperative Conversion of CO2 to Cyclic Carbonate

“…For example, coordination ionic polymers were constructed with imidazolium-substituted Al− salen ligand moieties, providing excellent catalytic activity under 373 K and 3 MPa. 32 Al−salen porous ionic polymers were prepared via free-radical copolymerization reaction to act as bifunctional catalysts in the CO 2 cycloaddition reaction, exhibiting good performance under 313 K and 1 MPa. 33 Compared with traditional metallosalen catalysts, integrating metallosalen complexes into the porous framework with free mobile anions can provide a cooperative environment for promoting the activity in the CO 2 cycloaddition reaction.…”