(PMo_(12))(HPy)_(3)的合成、表征及催化氧化碘离子性能

Synthesis,characterization of (PMo_(12))(HPy)_(3) and its catalytic oxidation property of iodide ion

采用水热法合成了一例新的多酸基有机-无机杂化物非均相催化剂,并通过X-射线单晶衍射、傅里叶变换红外光谱(IR)、热重分析测试(TG)、X-射线衍射分析(XRD)、元素分析对其进行了表征。X-射线单晶衍射分析表明,化合物的结构式为(PMo_(12)O_(40))(C_(5)H_(6)N)_(3)[简写为(PMo_(12))(HPy)_(3),其中PMo_(12)表示PMo_(12)O_(40),HPy表示C_(5)H_(6)N],属于正交晶系,Cmca空间群,晶胞参数a=1.91031(8)nm、b=1.53822(6)nm、c=1.46063(6)nm、α=β=γ=90°、V=4.2920(3)nm^(3)、Z=4、R_(1)=0.0629、wR_(2)=0.1324。化合物由2-吡啶甲酸在高温高压下原位脱羧后形成的质子化的3个吡啶环、1个经典的Keggin型[PMo_(12)O_(40)]^(3-)构成,每个次级单元之间通过静电等相互作用进一步形成一维(1D)~二维(2D)结构。催化研究表明:(PMo_(12)O_(40))(C_(5)H_(6)N)_(3)在催化过氧化氢氧化碘离子为碘单质过程中,其化学反应动力学近似准一级反应,反应速率高达1.205×10^(-5)mol/(L·s),相对于室温下未添加催化剂时提高了1839.7倍,该非均相催化剂重复使用5次后转化率仍高达99.96%,表现出较好的催化活性与可重复性。

A new polyoxometalate⁃based organic⁃inorganic hybrid heterogeneous catalyst was synthesized by hydrothermal synthesis,and it was characterized by X-ray single crystal diffraction,fourier transform infrared spectroscopy(IR),thermo⁃gravimetric analysis(TG),X-ray diffraction analysis(XRD)and elemental analysis.X-ray single crystal diffraction analysis showed that the structural formula of the compound was(PMo_(12)O_(40))(C_(5)H_(6)N)_(3)[short for(PMo_(12))(HPy)_(3),PMo_(12) was PMo_(12)O_(40),HPy was C_(5)H_(6)N],which was belonged to orthorhombic system,Cmca space group,unit cell parameters a=1.91031(8)nm,b=1.53822(6)nm,c=1.46063(6)nm,α=β=γ=90°,V=4.2920(3)nm^(3),Z=4,R_(1)=0.0629,wR_(2)=0.1324.The compound was composed of three protonated pyridine rings and one classical Keggin type[PMo_(12)O_(40)]^(3-)after in⁃situ de⁃carboxylation of 2-picolinic acid under high temperature and high pressure,and each secondary unit was formed by electro⁃static and other interactions to form one⁃dimensional(1D)to two⁃dimensional(2D)structures.Catalytic studies showed that:(PMo_(12))(HPy)_(3) in the process of catalyzing the oxidation of iodide ion to iodine element in hydrogen peroxide,the chemical reaction kinetics was approximately a first⁃order reaction,and the reaction rate was as high as 1.205×10^(-5) mol/(L·s),which was 1839.7 times higher than that no catalyst was added.When the heterogeneous catalyst was reused for 5 times,the con⁃version rate was still as high as 99.96%,showing good catalytic activity and repeatability.