非水溶液中有序介孔磷酸盐分子筛M-Zr-P-O(M=Ca,Al)合成及表征

Synthesis and Characterization of Ordered Mesoporous Phosphates MZrPO(M=Ca,Al) in Nonaqueous Solution

以三嵌段聚合物F127为模板剂,乙醇为溶剂,利用溶剂挥发诱导自组装法合成了Ca-Zr-P-O和Al-Zr-P-O有序介孔多金属磷酸盐分子筛。采用N_2吸附-脱附分析、扫描电子显微镜和小角X射线衍射分析了材料的介孔结构的有序性及其热稳定性;通过红外光谱、魔角核磁共振、X射线光电子能谱和紫外可见漫反射光谱研究了2种介孔分子筛骨架结构中金属离子的存在状态。结果表明:2种磷酸盐分子筛,均属于二维六方有序介孔结构,骨架结构为非晶态,平均孔径介于7~10 nm,比表面积达120~260 m^2/g。Ca^(2+)和Al^(3+)均匀分散在分子筛的孔壁骨架结构中,Ca^(2+)对[ZrO_4]配位结构影响较大,Al^(3+)具有良好的配位能力且不影响[ZrO_4]配位结构。Ca^(2+)和Al^(3+)性质上的差异导致2种介孔磷酸盐材料具有不同的热稳定性:Ca_(0.25)Zr_(0.75)PO经700℃焙烧5 h后能维持有序的介孔结构,Al_(0.5)Zr_(0.5)PO经800℃焙烧仍能保持有序介孔结构。

Mesoporous multi–metal phosphates of CaZrPO and AlZrPO were synthesized by a facile evaporation–induced self–assembly （EISA） method with an amphiphilic block copolymer, F127 as a template and ethanol as a solvent. The mesoporous structures and thermal stability were characterized by N2 adsorption–desorption analysis, transmission electron microscopy and small angle X–ray diffraction. The chemical state and coordination modes of metal ions in frameworks of these two mesoporous phosphates were determined by Fourier transform infrared spectroscopy, magic angle spinning nuclear magnetic resonance, X–ray photoelectron spectroscopy and UV–Vis diffuse reflectance spectroscopy. The results indicate that the two mesoporous phosphates both exhibit amorphous pore wall and two–dimensional hexagonal structure with average pore diameters of 7~10nm and specific surface area of 120~260 m2/g. Calcium and aluminum ions are uniformly dispersed in the pore–wall framework and the calcium ion has an influence on the Zr–O tetrahedral coordination unit, while aluminum ion has little influence. The mesoporous phosphates with CaZrPO calcined at 700 ℃ and AlZrPO calcined at 800 ℃ both possess a great thermal stability. The difference of coordination capability between the two metal cations could be due to their different thermal stabilities.