离子热法合成沸石咪唑骨架材料及其溶解-结晶机理研究

Ionothermal synthesis of zeolitic imidazolate frameworks and the synthesis dissolution-crystallization mechanism

基于沸石咪唑骨架材料在离子液体和低共熔溶剂中冷却结晶的析出方式,开发了一种离子热法合成沸石咪唑骨架材料的新途径,采用X射线衍射、扫描电镜、核磁共振光谱、红外光谱以及热重分析等方法对制备的产物进行了表征,研究了合成条件对产物结晶度、尺寸和形貌的影响,探讨了沸石咪唑骨架材料在离子热合成体系中的溶解-结晶析出机理.研究发现,冷却速率能够影响产物形貌,急速冷却时,sod(RCSR代码)型产物的形貌为球形,zni(RCSR代码)型产物为棒状或平板状;程序控制冷却时,sod型产物的形貌为多面体,zni型产物呈团簇状.

A cooling-induced crystallization process was used to synthesize sod （RCSR symbol）-and zni （RCSR symbol）-type zeolitic imidazolate frameworks （ZIFs） ionothermally in 1-ethyl-3-methylimidazolium bromide ionic liquid and a urea-choline chloride deep eutectic solvent. The products were charac-terized by X-ray diffraction, scanning electron microscopy, nuclear magnetic resonance spectrosco-py, infrared spectroscopy and thermal gravimetric analysis. The effect of the synthesis conditions on the crystallinity, size and morphology of the product was studied. The dissolution-crystallization mechanism of ZIFs was discussed. The cooling rate affected the product morphology. When the synthesis solution was cooled by rapid cooling, the shape of the sod-type product was spherical and the morphology of the zni-type product was rod-like or plate-like. With a programmed cooling, the sod-type product was polyhedron in shape and the zni-type product was in the form of clusters.