新穎水相反向擴散植晶法合成類沸石咪唑酯骨架-8薄膜於陶瓷中空纖維基材在氣體分離上的應用

類沸石咪唑酯骨架-8(ZIF-8)是最佳的ZIF結構之一因其具備適合如氫氣/甲烷、二氧化碳/氮氣等氣體分離的微孔結構(0.34奈米)。近五年來已有大量研究投入ZIF-8薄膜製備並加速其邁向商業化的階段，然而目前仍缺乏一個可靠且實際的製備程序來完成商業化，本研究提出一新穎水相反向擴散植晶法搭配環保的水相二次長晶將ZIF-8薄膜合成於氧化鋁中空纖維基材上，並達到工業上對量產、經濟性及環保程序的需求。　　在基材表面上覆蓋均勻的晶種層一直是在二次長晶法中要製備無缺陷ZIF-8薄膜的重要條件，而經由此新穎水相反向擴散植晶法可容易地達成。此外，基材的表面性質也被發現在合成均勻晶種層中具有重要的影響。我們探討了二次長晶所用的反應溶液濃度與二次長晶溫度對薄膜效能的影響，並找出在反應溶液濃度為鋅-二甲基咪唑比例1:50及合成溫度為攝氏50度是最適化的製備參數，除此之外，我們採用活化乾燥程序來移除殘留於薄膜孔洞中的溶液並防止傳統乾燥因溶液揮發過快對ZIF-8薄膜微孔結構造成的缺陷。　　本研究以單成分氣體通量測試(包含氦氣、二氧化碳、氮氣和六氟化硫)來檢驗所製備之ZIF-8薄膜的品質，最後，我們成功製備出具有二氧化碳/氮氣理想選擇比高達9.14且擁有相當高二氧化碳通量(2.66 × 10-7 mol m-2 s-1 Pa-1)與氦氣/六氟化硫有50.57理想選擇比(氦氣通量3.01 × 10-7 mol m-2 s-1 Pa-1)的高性能ZIF-8薄膜，這也表示本研究所提出的可量產製備方法是極有發展潛力且可靠的。

關鍵字

反向擴散；二次長晶；類沸石咪唑酯骨架-8 ；氧化鋁中空纖維；氣體分離

並列摘要

Zeolitic imidazolate framework ZIF-8 is one of the best known ZIF structures due to its small aperture size (0.34 nm) which is suitable for the most concerned gas separations, such as H2/CH4 and CO2/N2. Tons of researchers have devoted to preparing the ZIF-8 membranes in the past five years, which makes the ZIF-8 membranes step up to commercialization stage. However, the absence of a reliable and practical preparation process results in a difficulty in commercializing the ZIF-8 membranes. In this study, we proposed a novel counter diffusion seeding method combining with an environment-friendly aqueous secondary growth to synthesize the ZIF-8 membranes on the alumina hollow fiber substrates, which is a scalable, economical and green process practically meeting the industrial requirement. A uniform seeded layer on the substrate, which has been considered as a crucial factor for making the defect-free ZIF-8 membranes by the secondary growth method, could be simply achieved by this novel counter diffusion seeding method. Besides, surface property of the substrate was also demonstrated to play an important role in forming a uniform seeded layer. The effects of the concentration of secondary growth solution and the synthesis temperature for secondary growth on the membrane quality were investigated to find out the optimum synthesis conditions which is using the secondary growth solution with zinc-hmin ratio of 1:50 and synthesizing it at 50 ºC. Additionally, activation drying process was performed to prevent the solvent filled ZIF-8 membranes from forming defects in traditional drying process. To examine the quality of the as-prepared ZIF-8 membranes, the single gas (He, CO2, N2, and SF6) permeation test was conducted. Finally, high quality ZIF-8 hollow fiber membranes can be obtained, achieving a CO2/N2 ideal separation factor as high as 9.14 with a quite high CO2 permeance (2.66 × 10-7 mol m-2 s-1 Pa-1) and the He/SF6 ideal separation factor of 50.57 (with He permeance 3.01 × 10-7 mol m-2 s-1 Pa-1), which demonstrates the scalable preparation process proposed in this study is promising and reliable.

並列關鍵字

counter diffusion ； secondary growth ； ZIF-8 ； alumina hollow fiber substrates ； gas separation

參考文獻

1. M. Shah, M.C. McCarthy, S. Sachdeva, A.K. Lee, and H.-K. Jeong, Current Status of Metal-Organic Framework Membranes for Gas Separations: Promises and Challenges. Industrial & Engineering Chemistry Research, 2012. 51(5): p. 2179-2199.

2. L.M. Robeson, The upper bound revisited. Journal of Membrane Science, 2008. 320(1-2): p. 390-400.

3. L.Q. Ma, J.Y. Lee, J. Li, and W.B. Lin, 3D metal-organic frameworks based on elongated tetracarboxylate building blocks for hydrogen storage. Inorganic Chemistry, 2008. 47(10): p. 3955-3957.

4. R.E. Morris and P.S. Wheatley, Gas storage in nanoporous materials. Angewandte Chemie-International Edition, 2008. 47(27): p. 4966-4981.

5. Y.H. Hu and L. Zhang, Hydrogen Storage in Metal-Organic Frameworks. Advanced Materials, 2010. 22(20): p. E117-E130.

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新穎水相反向擴散植晶法合成類沸石咪唑酯骨架-8薄膜於陶瓷中空纖維基材在氣體分離上的應用

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