杂原子磷酸铝分子筛晶化过程的原位XAFS和DFT理论研究

THE in situ XAFS AND DFT COMPUTATION ON INCORPORATION OF METAL IONS INTO AlPO4-5 FRAMEWORK

采用原位X-射线吸收光谱的方法，结合密度泛函的理论研究，考察了杂原子磷酸铝分子筛水热晶化过程中Mn^2＋,Fe^3＋,Co^2＋,Ni^2＋等杂原子由骨架外向骨架内迁移的变化规律。实验中采用了自主设计、用于原位表征的分子筛晶化池，该晶化池可同时满足XAFS表征和分子筛水热晶化过程的要求。研究结果表明，在水热晶化的升温过程中，杂原子经历了由骨架外六配位向骨架四配位的转变，其转变规律与杂原子的离子半径、价态有关；合成体系中Si、F-^的存在显著地影响了杂原子的转变途径。

The in situ X-ray absorption spectroscopy characterization and DFT computation were carried out to get insight into the crystallization process of metal ions substituted AlPO4-5 （metal ions Me= Mn^2＋ , Fe^3＋ , Co^2＋ , Ni^2＋ ）. A special synthesis cell was designed to meet the demands of both the in situ XAFS characterization and the hydrothermal process. The transformation process of the metal ions from 6-fold to 4-fold coordination structure was influenced by the metal ion size and covalence, and the existence of Si and F in the precursor gel changed the synthesis process considerably.