Karimi Babak, Ghaffari Bahareh, Vali Hojatollah
Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), No. 444, Prof. Yousef Sobouti Boulevard, P.O. Box 45195-1159, Zanjan 45137-66731, Iran; Research Centre for Basic Sciences & Modern Technologies (RBST), Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran.
Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), No. 444, Prof. Yousef Sobouti Boulevard, P.O. Box 45195-1159, Zanjan 45137-66731, Iran.
J Colloid Interface Sci. 2021 May;589:474-485. doi: 10.1016/j.jcis.2020.12.111. Epub 2020 Dec 31.
It is expected that incorporation of 2, 2, 6, 6-tetra-methyl piperidine-N-oxyl radical (TEMPO) and an imidazolium bromide bearing hydrophilic triethylene glycol (TEG) groups on FeO@SiO core-shell may not only result in a novel highly water-dispersible/magnetically separable multi-functional catalyst system for metal-free aerobic oxidation of alcohols, which operates through a synergistic relay pathway, but it could potentially provide a strong platform for simultaneous separation and recycling of all components.
The catalyst was prepared by anchoring TEMPO moieties onto a magnetic core-shell FeO@SiO functionalized with an ionic liquid bearing TEG groups. The materials was characterized using transmission electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption-desorption isotherms, thermal gravimetric analysis, and elemental analysis. The performance of the catalyst was evaluated and quantitatively measured in the aerobic oxidation of alcohols in water.
The catalyst exhibited excellent and stable colloidal dispersion in water and high performance in the aerobic oxidation of various types of alcohols under metal- and halogen-free reaction conditions. As hypothesized, strong synergistic effect between functionalized components was seen in the described reaction. The catalyst displayed excellent dual-adjustable-selectivity in the oxidation of primary alcohols to either the corresponding aldehydes or carboxylic acids by tuning the reaction solvent and/or reaction time and excellent recycling behavior through a "double-separation-strategy".
预计在FeO@SiO核壳结构上引入2,2,6,6-四甲基哌啶-N-氧基自由基（TEMPO）和带有亲水性三甘醇（TEG）基团的咪唑溴化物，不仅会产生一种新型的高度水分散性/磁可分离的多官能催化剂体系，用于无金属的醇类有氧氧化反应，该反应通过协同接力途径进行，而且它可能为所有组分的同时分离和循环利用提供一个强大的平台。
通过将TEMPO部分锚定在由带有TEG基团的离子液体功能化的磁性核壳FeO@SiO上制备催化剂。使用透射电子显微镜、傅里叶变换红外光谱、氮吸附-脱附等温线、热重分析和元素分析对材料进行表征。在水中醇类的有氧氧化反应中评估并定量测量催化剂的性能。
该催化剂在水中表现出优异且稳定的胶体分散性，并且在无金属和无卤素的反应条件下，对各种类型的醇类有氧氧化反应具有高性能。如假设的那样，在所描述的反应中，功能化组分之间存在很强的协同效应。通过调节反应溶剂和/或反应时间，该催化剂在将伯醇氧化为相应的醛或羧酸的反应中表现出优异的双重可调选择性，并且通过“双分离策略”表现出优异的循环性能。
