Metal–Organic Gels Derived from Iron(III) and Pyridine Ligands: Morphology, Self‐Healing and Catalysis for Ethylene Selective Dimerization

Abstract

Metal‐organic gels showing potential application in catalysis have received much concern. In this work, we designed and synthesized two metal‐organic gels based on coordination between FeIII and pyridine ligands at room temperature. The gels were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to reveal their assembly structures and morphologies, and it was found the metal‐organic gel derived from di‐topic ligand was composed of three‐dimensional network of nanofibers, while the gel derived from tri‐topic ligand was constituted of sponge‐like structure with amorphous phase. Rheological analysis showed the gel consisting of nanofiber networks displayed self‐healing property. The gels were used as catalysts for selective ethylene dimerization, and the optimum catalysis results of the gel with nanofibers reached the maximal catalytic activity of 1.48×105 g/(mol Fe⋅h) with C4 yield more than 90 %, whereas the sponge‐like gel only gave 38 % C4 products at the same condition. The higher dimerization selectivity of the former FeIII gel was attributed to its regular assembly structure and lower steric hindrance of the surface metal sites. Due to its catalytic activity, high selectivity and preparation simplicity, the FeIII gel might be potentially applicable for the preparation of C4 α‐olefins.

Research progress of iron-based catalysts for selective oligomerization of ethylene

“…However, iron complexes are sensitive to temperature, so the catalytic time of iron complexes in oligomerization reaction is relatively short. 77,93 Juan Cámpora and other coworkers 122 found that the environment around the active center had signicant inuences on ligands in iron complexes. These inuencing factors involve not only temperature, but also reaction pressure and types of co-catalysts etc.…”

“…Homogeneous iron-based catalysts have the advantages of high activity 119,120 and selectivity. 121 Furthermore, structural alterations of complexes 70,71,[77][78][79][80][81][82][83][84][85][86][87][88][89] can be easily made. However, iron complexes are sensitive to temperature, so the catalytic time of iron complexes in oligomerization reaction is relatively short.…”

Hierarchical porous metal–organic gels and derived materials: from fundamentals to potential applications

“…In another report, ditopic and tritopic pyridine linkers were combined with Fe 3+ ions to form MOGs for utilization as catalysts for selective ethylene dimerization to C4 α-olefins. 308 Owing to the dispersion of metal sites in the nanofibrous network structure, it exhibited >90% yield for the selective ethylene dimerization. In comparison, the Fe-MOG based on the tritopic linker showed only 38% yield with comparatively low C4 product selectivity.…”

“…The potential of MOGs as catalysts or catalyst supports is not only limited to the above mentioned reactions but also has found its use for various other reactions, including condensation, dimerization, coupling and transesterification reactions. 297,298,307,308 For instance, Lee et al constructed a metal-organic xerogel from a cyclohexane-based tripyridine linker and Cd 2+ ions as a Knoevenagel condensation catalyst. 307 By taking the Cd 2+ based xerogel as a base catalyst for benzaldehyde condensation in the presence of nitrile compounds with different activity like cyano-acetic acid tert-butyl ester, malononitrile and ethyl cyanoacetate, a good product yields of 75%, 80% and 73%, respectively, were achieved.…”

Self-Healing Binder for High-Voltage Batteries

“…The process conditions of the selected monomer are very easy to achieve, prepared at the temperature of 180–220 °C. The hydroxyl and ester groups in its structure are capable of forming strong hydrogen, ion-dipole, and other bonds with active particles and the current collector, thereby producing intense adhesions. ,, Its low glass transition temperature (−60 °C), amorphous structure, and low cross-link density also enhance the mobility of the polymer chain at 40 °C, which facilitates rapid structural recovery and maintenance of strong adhesion, as illustrated in Figure . − …”