Reaction conditions for the synthesis of an ε-Keggin-type polyoxometalate-based 3D framework, (NH4)2.8H0.9[ε-VMo9.4V2.6O40Bi2]·7.2H2O (denoted as MoâVâBi oxide), are studied. It is found that the reaction time, temperature, pH of the solution, and starting compounds affect the production of MoâVâBi oxide. The crystal size of MoâVâBi oxide is controllable by changing bismuth compounds. Nanometer-sized MoâVâBi oxide is produced using a water-soluble bismuth compound, Bi(NO3)3·5H2O, whereas micrometer to submicrometer-sized MoâVâBi oxide is produced using Bi(OH)3, which is less soluble in water. The particle size of the material affects the properties of the material, such as surface area and catalysis. The investigation of the formation process of the material is carried out with Raman spectroscopy, which indicates that mixing (NH4)6Mo7O24·4H2O, VOSO4·5H2O, and bismuth ions in water produces the ε-Keggin polyoxovanadomolybdate together with a ball-shaped polyoxovanadomolybdate, [Mo72V30O282(H2O)56(SO4)12]36â (denoted as Mo72V30}). By heating the reaction mixture, the ε-Keggin polyoxovanadomolybdate assembles with bismuth ions to form MoâVâBi oxide, whereas Mo72V30} assembles with other vanadium and molybdenum ions to form orthorhombic MoâV oxide.
研究了合成一种基于ε-Keggin型多氧
金属酸盐的3D框架(NH4)2.8H0.9[ε-VMo9.4V2.6O40Bi2]·7.2 (记为Mo-V-Bi氧化物)的反应条件。研究发现,反应时间、温度、溶液的pH值和起始化合物会影响Mo-V-Bi氧化物的生成。通过改变
铋化合物,可以控制Mo-V-Bi氧化物的晶体尺寸。使用
水溶性
铋化合物Bi(
NO3)3·5 可以生成纳米大小的Mo-V-Bi氧化物,而使用Bi(OH)3可以生成微米到亚微米大小的Mo-V-Bi氧化物,Bi(OH)3在
水中的溶解度较低。材料的粒径会影响材料的性质,如表面积和催化性。使用拉曼光谱仪对材料的形成过程进行了研究,结果表明,将(NH4)6Mo7O24·4 、VOSO4·5 和
铋离子混合在
水中,可以生成ε-Keggin型多氧
钒钼酸盐和球形多氧
钒钼酸盐[Mo72V30O282(
H2O)56(SO4)12]36∙(记