Metal-Organic Gels Derived from Iron(III) and Pyridine Ligands: Morphology, Self-Healing and Catalysis for Ethylene...

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 Fe^III 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 Fe^III 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 Fe^III gel might be potentially applicable for the preparation of C₄ α-olefins.