Synthesis of magnetically recyclable ZIF-8@SiO{sub 2}@Fe{sub 3}O{sub 4} catalysts and their catalytic performance for Knoevenagel reaction
Synthesis of magnetically recyclable ZIF-8@SiO{sub 2}@Fe{sub 3}O{sub 4} catalysts and their catalytic performance for Knoevenagel reaction
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DOI：
10.1016/j.jssc.2014.06.017
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发表时间：
2015-03
影响因子：
3.3
通讯作者：
Qingyuan Li;Sai Jiang;M. Ammar;Qingmin Zhang;Junlei Yan
中科院分区：
文献类型：
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作者：
Qingyuan Li;Sai Jiang;M. Ammar;Qingmin Zhang;Junlei Yan
采用原位法将磁性SiO2@Fe3O4纳米粒子包覆于ZIF-8中，制备了新型磁性ZIF-8@SiO2@Fe3O4催化剂。采用TEM、SEM、XRD、FT-IR、VSM、N2吸附/脱附、CO2-TPD等技术对催化剂进行了表征。评价了催化剂对对氯苯甲醛与丙二腈的Knoevenagel反应的催化活性和回收性能。结果表明，磁性ZIF-8@SiO2@Fe3O4催化剂具有较大的比表面积和适宜的超顺磁性，对Knoevenagel反应具有良好的催化活性。在35.8%ZIF-8@SiO2@Fe3O4（MZC-5）催化剂上，25 °C反应4 h，对氯苯甲醛的转化率可达98%左右，产物的选择性可达99%左右。磁性ZIF-8@SiO2@Fe3O4催化剂也具有良好的基质适应性。在反应之后，催化剂可以通过外部磁体容易地从反应混合物中分离。回收的催化剂可重复使用5次，对氯苯甲醛的转化率可保持在90%以上。
Novel magnetic ZIF-8@SiO2@Fe3O4catalysts were synthesized by encapsulating magnetic SiO2@Fe3O4nanoparticles into ZIF-8 through in situ method. The structures of the catalysts were characterized by TEM, SEM, XRD, FT-IR, VSM, N2adsorption/desorption and CO2-TPD technology. The catalytic activity and recovery properties of the catalysts for the Knoevenagel reaction ofp-chlorobenzaldehyde with malononitrile were evaluated. The results showed that the magnetic ZIF-8@SiO2@Fe3O4catalysts had the larger surface areas, the suitable superparamagnetism, and good catalytic activity for Knoevenagel reaction. The conversion ofp-chlorobenzaldehyde can reach ~98% and the selectivity of the production can reach ~99% over35.8%ZIF-8@SiO2@Fe3O4(MZC-5) catalyst under the reaction condition of 25 °C and 4 h. The magnetic ZIF-8@SiO2@Fe3O4catalysts also had good substrates adaptation. After reaction, the catalyst can be easily separated from the reaction mixture by an external magnet. The recovery catalyst can be reused five times and the conversion ofp-chlorobenzaldehyde can be kept over 90%.