Abstract
Abstract The in situ X-ray Absorption Spectroscopy (XAS) was employed to probe the incorporation of transition metal ions, such as Mn 2+ , Fe 3+ , Co 2+ and Ni 2+ , from precursor gel to AlPO 4 -5 framework in hydrothermal synthesis process. With the crystallization, the number of coordinated oxygen around metal ions changes from 6 to 4, associated with a decrease in the coordination distance of metal ions to oxygen, as revealed by XAS. However, these metal ions are different in the incorporation behaviour and mechanism. The transition of Co 2+ into the tetrahedral framework of AlPO 4 -5 is completed at 150 o C with the emergence of long-range ordered microporous structure, while the incorporation of Mn 2+ and Fe 3+ is much more difficult and starts after the build-up of microporous structure. On the other hand, the existence of Si 4+ in the precursor gel has also considerable influences on the synthesis process.
Published Version
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