催化学报 ›› 2016, Vol. 37 ›› Issue (12): 2106-2113.DOI: 10.1016/S1872-2067(16)62562-7

• 论文 • 上一篇    下一篇

核壳结构Fe3O4@UiO-66-NH2磁性纳米复合材料的合成及其催化Knoevenagel缩合反应性能

张艳梅a, 戴田霖b, 张帆a, 张静b, 储刚b, 权春善a   

  1. a 大连民族大学生命科学学院, 辽宁大连 116600;
    b 辽宁石油化工大学化学与材料科学学院, 辽宁抚顺 113001
  • 收稿日期:2016-08-25 修回日期:2016-09-14 出版日期:2016-12-27 发布日期:2016-12-27
  • 通讯作者: Yanmei Zhang
  • 基金资助:

    国家自然科学基金(21203017);中国科学院大连化学物理研究所催化基础国家重点实验室开放基金(N-11-03);辽宁省高等学校优秀人才支持计划;中央高校基本科研业务费专项资金(DC201502020304).

Fe3O4@UiO-66-NH2 core-shell nanohybrid as stable heterogeneous catalyst for Knoevenagel condensation

Yanmei Zhanga, Tianlin Daib, Fan Zhanga, Jing Zhangb, Gang Chub, Chunshan Quana   

  1. a College of Life Science, Dalian Minzu University, Dalian 116600, Liaoning, China;
    b School of Chemistry and Material Science, Liaoning Shihua University, Fushun 113001, Liaoning, China
  • Received:2016-08-25 Revised:2016-09-14 Online:2016-12-27 Published:2016-12-27
  • Contact: Yanmei Zhang
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21203017), Open Fund of State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences (N-11-3), Program for Liaoning Excellent Talents in University (LNET), and the Fundamental Research Funds for the Central Universities (DC201502020304).

摘要:

金属有机骨架(MOF)材料是由过渡金属离子与有机配体通过配位键连接构成的高度有序的超分子化合物.这类材料比表面积大,孔隙率高,热稳定性好,而且具有规整可调控的孔结构、易于功能化的骨架金属离子和有机配体,在多相催化领域具有潜在应用前景.将纳米尺寸的MOF材料等多孔材料作为催化剂,可以提高反应传质效率,从而提高催化反应活性,但纳米MOF催化剂的分离和回收困难.将磁性纳米粒子和MOF材料组装成核壳结构的磁性MOF材料,不仅可简化催化剂的分离回收,而且通过控制壳层材料的厚度可以实现催化剂的高活性和高选择性.
我们曾将磁核Fe3O4纳米粒子交替放入含有一种MOF材料前体的DMF溶液中,采用层层组装法制备了磁性Fe3O4@UiO-66-NH2纳米复合材料.经过十步组装后的材料的透射电镜(TEM)结果证实为核壳结构.但未出现明显的UiO-66-NH2的X射线衍射(XRD)特征峰,说明壳层材料UiO-66-NH2的结晶度较低;同时由于其孔结构的破坏或堵塞,在反应中出现明显失活.
本文进一步改进自组装方法制备了核壳结构的磁性Fe3O4@UiO-66-NH2纳米复合材料,用XRD、傅里叶变换红外光谱(FT-IR)、TEM、扫描电镜(SEM)和氮气吸附等方法对材料的组成和结构进行了表征,并考察了其在Knoevenagel缩合反应中的催化性能.结果表明,所制材料是以Fe3O4为核,以UiO-66-NH2为壳的核-壳结构材料.经三次组装后出现了一系列UiO-66-NH2的XRD特征峰,说明采用新方法制备的复合材料中壳层材料UiO-66-NH2结晶度高,晶体结构规整.N2吸附-脱附结果表明,材料具有较高的比表面积和孔容.
该复合材料在Knoevenagel缩合反应中表现出与纳米UiO-66-NH2相当或更好的催化活性和选择性,而且因壳层材料的孔道限阈效应而对底物表现出尺寸选择性.由于材料结晶度和晶体结构规整度的提高,催化剂稳定性更好,通过简单磁性分离即可分离和回收催化剂,循环使用4次而未出现明显失活.相对于本课题组之前报道的Fe3O4@CuBTC-NH2,Fe3O4@IRMOF-3和Fe3O4@UiO-66-NH2材料,本文所制的Fe3O4@UiO-66-NH2是一类结构更加稳定的高效固体碱催化剂.

关键词: 金属有机骨架材料, UiO-66-NH2, 四氧化三铁, 多相催化剂, Knoevenagel缩合反应, 磁性分离

Abstract:

Magnetic separation is an attractive alternative to filtration or centrifugation for separating solid catalysts from a liquid phase. Here, core-shell Fe3O4@UiO-66-NH2 nanohybrids with well-defined structures were constructed by dispersing magnets in a dimethylformamide (DMF) solution containing two metal-organic framework (MOF) precursors, namely ZrCl4 and 2-aminobenzenetricarboxylic acid. This method is simpler and more efficient than previously reported step-by-step method in which magnets were consecutively dispersed in DMF solutions each containing one MOF precursor, and the obtained Fe3O4@UiO-66-NH2 with three assembly cycles has a higher degree of crystallinity and porosity. The core-shell Fe3O4@UiO-66-NH2 is highly active and selective in Knoevenagel condensations because of the bifunctionality of UiO-66-NH2 and better mass transfer in the nano-sized shells. It also has good recycling stability, and can be recovered magnetically and reused at least four times without significant loss of catalytic activity and framework integrity. The effects of substitution on the reactivity of benzaldehyde and of substrate size were also investigated.

Key words: Metal-organic framework, UiO-66-NH2, Fe3O4, Heterogeneous catalyst, Knoevenagel condensation, Magnetic separation