| Metal-organic frameworks (MOFs) are a new type of hybrid organic-inorganic supramolecular materials with orderly porous structure. These materials possess high specific surface areas, adjustable pore size and easy functionalization. These properties made MOFs ideal candidates in many fields such as catalysis, gas separation and storage, drug delivery as well as optical and electronic applications. However, there are extremely rare works on MOFs as polymerization catalysts. Siloxanes, as an important class of polymers, have been extensively applied in electronic and electrical field, textile industry, traffic and transportation, medical care, health due to their unique characters such as anti-aging property, high and low temperature resistance, electrial insulation property and hydrophobic property. This paper applied MOFs material in catalytic polymerization field. The roles of MOFs materials are explored during the polymerization process by a combination of physicochemical techniques such as the Fourier transform infrared spectroscopy (FT-IR), N2adsorption/desorption measurement, Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Melting point analysis and X-ray photoelectron spectra (XPS). Meanwhile, the obtained MOFs-siloxane composites combined the excellent properties of MOFs materials and siloxanes leading to the potential applications in various fields. The main works are summarized as follows:(1) ZIF-8, obtained by direct reaction of zinc hydroxide to2-methylimidazole at ambient temperature, was used in the polymerization of akylsiane (C)8H37SiH3, ODS) reaction. The effects of reaction temperature, time and amount used in the reaction, as well as the reaction mechanism were investigated. It tured out that the FT-IR spectrum of the product showed that the band owing to Si-H bonds of C18H37SiH3at2150cm-1declined. A new band at1110cm-1which corresponds to Si-O stretching appeared simultaneously. The peaks at1350-1500cm-1are associated with the entire imidazole ring stretching. An obvious peak corresponding to SiO2also appeared in XRD spectra of the product, indicating the existence of abundant Si-O bonds. These characterizations indicated that the polymerization of octadecylsilane occurred to some extent. After reaction,the XRD pattern of ZIF-8corresponded with the pure ZIF-8. It confirmed that the ZIF-8maintained its structure during the reaction. Moreover, the polymerization of octadecylsilane over ZIF-8could even occur at the room temperature to obtain uniform microspheres exhibiting Bird’s Nest morphology. These rose petal-like products were obtained when increasing the temperature and maintained their integrity even when the temperature increased to120℃. Besides, the reaction time and amount of catalyst had a little influence on the morphologies of the products. The obtained MOFs-siloxane composites exhibited better thermostability and hydrophobicity.(2) Two Cr-MOFs were syntesized by solvothermal method, named MIL-100(Cr) and MIL-101(Cr). Through some physicochemical techniques, we proved that the polymerization of octadecylsilane occurred when using the two Cr-MOFs as catalysts. The morphology of the polymerization products obtained by the reaction were agglomerated particles.(3) HKUST-1was prepared through a solvothermal method. The obtained samples were characterized by a series of physicochemical techniques and applied to the polymerization reaction. FT-IR and XRD results showed us that the polymerization of octadecylsilane occurred to some extent when using HKUST-1as a catalyst. The SEM showed the polymerization products had an irregularly blocky structure.In summary, MOFs materials were shown for the first time to be able to induce polymerization of alkylsilanes to fabricate3D microstructure. This work opened new perspectives on the use of MOFs in catalytic polymerization and in the development of a rational route to the multidimensional assembly of MOFs building blocks into desired structures or platforms. |
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