核-壳结构磁性金属有机骨架材料Fe3O4@UiO-66-NH2的合成、表征及催化性能
Core-Shell Magnetic Microsphere Fe3O4@UiO-66-NH2:Characterization and Application as Heterogeneous Catalyst
作者单位E-mail
戴田霖 辽宁石油化工大学化学与材料科学学院, 抚顺 113001
大连民族大学生命科学学院, 大连 116600 
 
张艳梅 大连民族大学生命科学学院, 大连 116600 ymzhang@dlnu.edu.cn 
储刚 辽宁石油化工大学化学与材料科学学院, 抚顺 113001  
张静 辽宁石油化工大学化学与材料科学学院, 抚顺 113001  
摘要: UiO-66-NH2是以Zr4+为金属,以2-氨基对苯二甲酸为配体制备得到的金属有机骨架材料,它是目前报道中具有较高热稳定性和化学稳定性的材料之一。本文以Fe3O4为核,以UiO-66-NH2为壳,采用层层自组装方法制备了核-壳结构的磁性金属有机骨架材料Fe3O4@UiO-66-NH2。利用X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)和氮气吸附等对其进行了表征,并考察了该磁性材料在克脑文盖尔(Knoevenagel)缩合反应中的催化性能。结果表明,该磁性材料Fe3O4@UiO-66-NH2为核-壳结构,壳层厚度约为100 nm,氨基含量为1.70 mmol·g-1。该磁性复合材料具有Fe3O4和UiO-66-NH2的双重功能,既可以磁性分离,又具有UiO-66-NH2的孔结构和催化性能。由于壳层材料中Lewis酸性位(Zr4+)和碱性基团(-NH2)的协同催化能力及其壳层的纳米尺寸效应,该磁性材料在Knoevenagel缩合反应中表现出和UiO-66-NH2纳米粒子相当的催化活性。而且,通过磁性分离实现催化剂的多次循环使用后,其结构没有明显变化。
关键词: 四氧化三铁  金属有机骨架材料  核-壳结构  克脑文盖尔缩合反应  磁性分离
基金项目: 国家自然科学基金(No.21203017)、国家重点实验室开放基金(No.N-11-03)、辽宁省高等学校优秀人才支持计划、中央高校基本研究业务费专项资金(No.DC201502020304)资助项目。
Abstract: Magnetic metal organic frameworks exhibit both magnetic characteristics and catalytic properties.However, their applications as heterogeneous catalysts are still very limited.Herein, a novel kind of core-shell structured Fe3O4@UiO-66-NH2 has been successfully fabricated by a layer-by-layer self assembly method which could be used as an active basic catalyst for Knoevenagel condensation.In a typical synthesis, Fe3O4 nanoparticals were synthesized by a solvothermal method and then surface modified with mercaptoacetic acid(MAA).Dispersing the MAA-modified Fe3O4 microspheres alternately in DMF solutions of ZrCl4(10 mmol·L-1) and 2-aminobenzenetricarboxylic acid DMF solution(10 mmol·L-1) at 120℃ for 2 h, Fe3O4@UiO-66-NH2 core-shell structured microspheres were successfully prepared as expected.Its core-shell structure was confirmed by XRD and TEM techniques, composition by SEM-EDS and the amine functionality proven by IR spectroscopy.The shell thickness is about 100 nm and its weight content is about 60%.Correspondingly, the amino content was calculated to be 1.7 mmol·g-1.The core-shell Fe3O4@UiO-66-NH2 is an ideal recyclable catalyst for Knoevenagel condensation that derive from a combination of a superparamagnetic core for efficient magnetic separation and a thin porous MOF shell for high catalytic activity.The remarkable activities for Knoevenagel condensation reactions are thanks to the cooperative action of amino groups and Lewis acid Zr4+ ions in UiO-66-NH2.Obvious solvents effect on the activity and stability was observed, and DMF was selected as good medium for recyclability for a sacrificial balance between activity and recyclability.The catalyst could be easily separated from the reaction mixture and reused without significant change in the catalytic activity after four reaction cycles.Furthermore, its structure and morphology was not changed after the reaction in DMF, confirmed by the XRD, SEM and TEM techniques.Therefore, such kind of MOF-based core-shell magnetic catalysts is expected to be used in large scale industrial applications, where separation and recycling are critically required to reduce the cost as well as waste production.Moreover, the catalyst preparation procedure is fairly simple and the catalysts contain no toxic materials, thus this catalyst is green and cheap.
Keywords: Fe3O4  metal organic frameworks  core-shell structure  Knoevenagel condensation  magnetic separation
投稿时间:2015-11-17 修订日期:2016-02-01
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戴田霖,张艳梅,储刚,张静.核-壳结构磁性金属有机骨架材料Fe3O4@UiO-66-NH2的合成、表征及催化性能[J].无机化学学报,2016,32(4):609-616.
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