【10th May】Solid-state NMR spectroscopy: A useful tool for porous materials characterization
日期:2013-05-10 阅读:928

题目:Solid-state NMR spectroscopy: A useful tool for porous materials characterization
报告人: Prof. Yining HuangDepartment of Chemistry, The University of Western Ontario, Canada
时间:2013510(星期五) 上午10:00
邀请人:陈接胜 教授(化学化工学院)

The research in Prof. Huang’s group has been focused on various porous materials. In this presentation, he will report their recent work on two areas:
1. Solid-state NMR characterization of metal-organic frameworks at ultrahigh magnetic field
The most exciting advance of porous materials in recent years is the discovery of a family of hybrid organic-inorganic solids known as metal-organic frameworks (MOFs). MOFs have high thermal stability, permanent porosity, a flexible framework and exceptionally high surface areas, leading to numerous important applications. Although the structures of many MOFs can be determined by single crystal X-ray diffraction, a significant number of MOF structures have to be refined from more limited powder XRD data due to the lack of suitable single crystals. In such cases an unambiguous structure solution requires additional information from complementary techniques such as solid-state NMR (SSNMR). Recently we have characterized a number of representative MOFs using multinuclear (Mg-25, In-115, Zr-91, Zn-67, La-129, Ti-/47/49, Ba-135, O-17, H-1 and C-13) SSNMR. The results allow us to directly address several important issues in MOF characterization including (a) resolving crystallographically non-equivalent sites in unit cell; (b) identifying chemically different species; (c) confirming the geometry around a metal center in the structure refined from powder XRD data; (d) probing the effect of adsorption of guest molecules on local metal environment; (e) examining the effect of activation (dehydration/desolvation) on the metal local structure.
2. Investigating the self-assembly of molecular sieves
Microporous materials are crystalline framework solids containing channels/cavities with molecular dimensions. They are widely used in industry as ion-exchangers, sorbents and catalysts. Due to the actual and potential industrial and technological applications there is considerable interest in the synthesis of microporous materials with novel framework structures. However, despite much data having been compiled on the synthesis conditions, the mechanisms of the formation of these materials are still not well understood at a molecular level. Here we will present some of our work on the crystallization of several representative silicoaluminophosphate (SAPO) based materials. We have characterized the intermediate phases formed during the crystallization by using C-13, P-31, Al-27, O-17, Si-29 and F-19 SSNMR with particular attention being paid to the structure of the intermediate phases.

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