Microporous Aluminophosphate ULM-6: Synthesis, NMR Assignment, and Its Transformation to AlPO4-14 Molecular Sieve

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• 作者：Dehua Wang ; Shutao Xu ; Miao Yang ; Yueying Chu ; Peng Tian ; Zhongmin Liu
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 9, 2016
• 年：2016
• 卷：120
• 期：22
• 页码：11854-11863
• 全文大小：690K
• 年卷期：0
• ISSN：1932-7455

文摘

A pure fluorinated aluminophosphate [Al₈P₈O₃₂F₄·(C₃H₁₂N₂)₂(H₂O)₂] (ULM-6) has been synthesized via an aminothermal strategy, in which triisopropanolamine (TIPA) is used as the solvent together with the addition of propyleneurea and HF. The ¹³C NMR spectrum demonstrates that 1,3-diaminopropane, the in situ decomposer of propyleneurea, is the real structure-directing agent (SDA) for ULM-6 crystals. The local Al, P, and F environments of the dehydrated ULM-6 are investigated by 1D and 2D solid-state NMR spectroscopy. The spatial proximities are extracted from ¹⁹F{²⁷Al}, ¹⁹F{³¹P}, ²⁷Al{¹⁹F}, and ³¹P{¹⁹F} rotational-echo double resonance (REDOR) NMR experiments as well as ¹⁹F → ³¹P heteronuclear correlation (HETCOR) NMR and {³¹P}²⁷Al HMQC NMR experiments, allowing a full assignment of all the ¹⁹F, ²⁷Al, and ³¹P resonances to the corresponding crystallographic sites. Moreover, it is found that the structure of ULM-6 is closely related to that of AlPO₄-14. A combination of high-temperature powder XRD, thermal analysis, and ¹⁹F NMR reveals that the removal of fluorine atoms at higher temperature is crucial to the phase transformation of ULM-6 to AlPO₄-14. The calcined product shows high CO₂/CH₄ and CO₂/N₂ selectivity with ratios of 15.5 and 29.1 (101 kPa, 25 °C), respectively.