介孔磷钨酸铯盐的液相组装及酸性研究

以磷钨酸(H₃PW₁₂O₄₀)和氯化铯(CsCl)为原料, 两亲型三嵌段共聚物F127为模板剂, 按不同的Cs/P比制备了一系列介孔磷钨酸铯盐(Cs_xH_3-xPW₁₂O₄₀, m-CsPW). 通过X射线粉末衍射(XRD)、 场发射扫描电子显微镜(FESEM)、 场发射透射电子显微镜(FETEM)、 N₂吸附-脱附测试和小角X射线散射(SAXS)等手段对所得样品进行了表征. 结果表明, 样品是由纳米微晶组装而成的晶态介孔材料. 以三甲基膦为探针分子, 通过³¹P魔角旋转固体核磁共振波谱(³¹P MAS NMR)测定了样品酸处理前后的酸密度和酸强度. 以5,7-二羟基-4-甲基香豆素的Pechmann缩合反应为模型反应, 考察了样品的酸性质与催化活性之间的关系.

Liquid Phase Assembly of Mesoporous CsxH3-xPW12O40 and Characterization of Their Acidity

A series of mesoporous Cs_xH_3-xPW₁₂O₄₀ samples（denoted as m-CsPW） has been prepared using H₃PW₁₂O₄₀， CsCl as raw materials and amphiphilic triblock copolymer F127 as template. The sampleswere characterized by means of powder X-ray diffraction（XRD）， field emission scanning electron microscopy （FESEM）， field emission transmission electron microscopy（FETEM）， N₂ adsorption-desorption measurement and small angle X-ray scattering（SAXS） spectroscopy. The results indicate that the m-CsPW particles consis-ting of crystallographically ordered nanocrystallites are mesoporous spherical materials. Acid density and strength of the samples before and after acid treatment were characterized by ³¹P magic-angle spinning NMR spectroscopy（³¹P MAS NMR） using trimethylphosphine as probe molecule. Taking the Pechmann condensation of 5，7-dihydroxy-4-methylcoumarin as a model reaction， the relationship between the acid properties of the samples and the catalytic activity of the reaction has been investigated.