小角度與廣角 X-ray 散射分析金屬有機框架材料之孔洞結構

在本研究當中，利用小角度與廣角散射技術來分析不同合成路徑的Cu-BTC金屬有機框架材料 (HKUST-1) 中不同尺度的孔洞結構。我們的目標是建立一套快速且低成本的方法，有效的量測出孔洞材料的比表面積，並進一步了解當水氣自HKUST-1孔洞中移除後的結構演變。主要的分析樣品為編號M700及Nano-sized，兩種樣品皆由工研院合作同仁合成提供，並利用已量產的商業化樣品 (編號C300) 作為比較的對象。動態 (in-situ) 的小角度與廣角散射量測資訊顯示出HKUST-1隨著溫度上升，水氣自材料孔洞中移除對其結構與晶相有著明顯的改變，藉由Beaucage模型擬合小角度散射曲線可將孔洞尺寸分佈以及比表面積做完整的定量分析，擬合結果指出不同層級的孔洞結構與比表面積有著一定程度的相依性，此分析技術可以使得我們了解在HKUST-1結構中何種尺度的孔洞是造成二氧化碳吸脫附循環性質好壞的關鍵。另外一方面，在廣角散射圖譜中有局部性的訊號增強，結合小角度散射的分析資訊綜合可知訊號增強是來自於除去HKUST-1孔洞中水氣以及晶粒成長的影響。廣角散射曲線利用GSAS套裝軟體進行結構重組，更可定量的顯現出當除去HKUST-1孔洞中水氣後會使晶格常數以及銅離子之間的間距縮短。

關鍵字

小角度；金屬有機框架材料；孔洞；比表面積

並列摘要

In this investigation, small-angle and wide-angle X-ray scattering (SAXS & WAXS) measurements were utilized to analyze porous structures at different scales for Cu-BTC metal-organic frameworks (HKUST-1) of varied size populations prepared by different synthesis routes. Our objective is to establish a fast and low-cost method for effectively measuring specific surface area of pores, and to understand the change of HKUST-1’s structure after dehydration. Two kinds of HKUST-1, M700 and Nano-size, were provided by ITRI. An in-situ SAXS/WAXS experiment demonstrates the effect of temperature on the concurrent evolutions of pore structure and crystal phase during the removal of water upon heating. The results were also compared to the commercial sample (C300). By simulation modeling of SAXS profiles, the pore size distribution and specific surface area could be quantitatively determined. Quantitative curve analysis of SAXS indicates that the hierarchical pore structures of MOFs have the size-dependent specific surface areas. This gives us more insights in understanding which scale of pore size within MOFs is dominant for controlling the ability of CO2 adsorption. On the other hand, HKUST-1 shows special peak intensity enhancement in WAXS result. Dehydration and grain growth are the two main reasons. GSAS refinement also reveals that the lattice constants and the Cu-Cu distance decreased after dehydration.

並列關鍵字

Small-Angle X-ray Scattering (SAXS) ； Wide-Angle X-ray Scattering (WAXS) ； Metal-organic framework (MOF) ； HKUST-1 ； Pore Structure

參考文獻

[22] M. Eddaoudi, M. Hesse, L. Lobree, U. Mueller, and O. M. Yaghi, "Epoxidation process using catalysts containing metal organic framework", ed: Google Patents, 2003.

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國際替代計量

小角度與廣角 X-ray 散射分析金屬有機框架材料之孔洞結構

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