Investigation of the formation process of zeolite-like 3D frameworks constructed with ε-Keggin-type polyoxovanadomolybdates with binding bismuth ions and preparation of a nano-crystal
作者:Zhenxin Zhang、Masahiro Sadakane、Toru Murayama、Wataru Ueda
DOI:10.1039/c4dt01227e
日期:——
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]·7.2H2O(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)3·5H2O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)6Mo7O24·4H2O、VOSO4·5H2O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