高朋召 吴迪 郑航博 陈会会 张佩

摘   要：采用不同結构的有机胺改性溶剂热法合成ZIF-8催化剂，探讨胺结构特性对ZIF-8催化Knoevenagel缩合反应活性的影响. 结果表明，有机胺改性后ZIF-8保持菱形十二面体结构，形貌规则与未改性材料无明显差别，1，2丙二胺、二乙烯三胺和三乙烯四胺改性ZIF-8后的BET比表面积分别为1 893 m2·g-1、1 885 m2·g-1和1 861 m2·g-1，较改性前下降约6.5 %，这主要是由于接枝在ZIF-8表面的有机胺堵塞了其孔道;采用乙醇作溶剂，催化剂添加量（摩尔分数）为0.6%（相对于苯甲醛用量），反应温度80 ℃，210 min时，1，2丙二胺改性ZIF-8对Knoevenagel反应的催化活性最高，α-氰基肉桂酸乙酯的产率达97.8%，循环10次后，产率依旧保持90 %以上，较未改性催化剂产率提高35.3 %. 对胺改性ZIF-8的催化机理研究表明：有机胺改性ZIF-8可增加其催化活性位点，而1，2丙二胺因链短，空间位阻小，其N活性位点更易与反应物接触，与ZIF-8上原有的咪唑N位点一起通过孤对电子与反应物苯甲醛的亚甲基上的 -H配位，从而显著提高催化剂的活性.

关键词：ZIF-8;Knoevenagel缩合反应;胺改性;机理;催化

中图分类号：O641                                  文献标志码：A   文章编号：1674—2974（2020）08—0124—09

Abstract：In this paper， different kinds of organic amines were used to modify ZIF-8 catalysts prepared via solvothermal method，and the effects of organic amine structural characteristics on the catalytic activity of ZIF-8 for Knoevenagel condensation reaction were discussed. The results show that ZIF-8 modified by organic amine still maintains the rhombohedral dodecahedron structure and possesses regular morphology，without obvious difference from that of unmodified materials. The BET specific surface areas of ZIF-8 modified by 1，2-propylenediamine，diethylenetriamine and triethylenetetramine are 1 893 m2·g-1，1 885 m2·g-1 and 1 861 m2·g-1，respectively， decreased by about 6.5% compared with that of the unmodified materials， mainly due to the blockage of pores for ZIF-8 by organic amines. When ethanol works as solvent， the amount of catalyst is 0.6 mol%（molar ratio to benzaldehyde），the reaction temperature is 80 ℃. When the reaction time keeps for 210 min，1，2-propanediamine modified ZIF-8 exhibits the highest catalyst activity，and the yield of ethyl α-cyanocinnamate reaches 97.8 %. After 10 cycles，the yield of this reaction is still up to 90 %，an increase of 35.3 % higher than that of unmodified ZIF-8. The studies on the catalytic mechanism of amine-modified ZIF-8 indicate that amines modified ZIF-8 can improve the amount of activity site，while 1，2-propanediamine has a shorter chain and less steric hindrance， making its N sites easier contact with reactants. It combines with the original imidazole N site on ZIF-8 to coordinate with α-H on the methylene of benzaldehyde through lone pair electrons，  therefore significantly improving the catalytic activity of the catalyst clearly.

Key words：ZIF-8;Knoevenagel condensation reaction;amine modification;mechanism;catalysis

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