低熔点柠檬酸/DMU混合物中磷酸铝骨架材料的合成与表征

SYNTHESIS AND CHARACTERIZATION OF ALUMINUM PHOSPHATE FRAMEWORK MATERIALS IN AN EUTECTIC MIXTURE OF CITRIC ACID AND DMU

以柠檬酸/1,3-二甲基尿素(DMU)形成的低熔点混合物作为反应介质,异丙醇铝(Al(OiPr)3)、H3PO4和HF为起始反应组分,制备出一种已知的链状磷酸铝化合物Al(HPO4)2F.(CH3NH3)2,系统地考察了F/Al、P/Al及晶化时间对最终产物的影响,并利用XRD、SEM、TG-DTA及CHN元素分析手段对合成样品进行了表征。结果表明,DMU的热分解产物甲胺对磷酸铝骨架的生成起到了结构导向作用,HF对产物的晶化过程具有重要作用,且参与了骨架的生成,最终产物为均一的片状晶体,尺寸在30μm左右。最佳合成条件为n(HF)∶n(Al(OiPr)3)∶n(H3PO4)∶n(Citric acid)∶n(DMU)=1∶1∶3∶20∶30、晶化温度373 K、晶化时间4 d。

By using the eutectic mixture of citric acid and N,N-dimethylurea （DMU） as reaction medium, aluminum isopropoxide（Al（OiPr）3）, H3PO4 and HF as starting reaction components, a known aluminum phosphate with chain structure, AI（HPO4）2F. （CH3NH3）2 was synthesized. The final products were characterized by XRD, SEM, TG-DTA and CHN methods. The synthetic conditions, such as F/Al, P/Al and crystallization time on the final products were systematically investigated, The results showed that the methylamine, derived from thermal decomposition of DMU, acted as the structure directing agent for the formation of aluminum phosphate framework. HF was also crucial to the product crystallization and finally incorporated into the framework. The obtained crystals were presented as an uniform sheet habit and its size was up to 30 μm. The optimized reaction conditions were n （HF） ： n（Al（OiPr） 3 ） ： n （ H3 PO4 ） ： n（eitric acid） ： n（DMU）=1 ： 1 ： 3 ： 20： 30, crystallization temperature and time of 373 K and 4 d, respectively.