工學院: 化學工程學研究所指導教授: 康敦彥羅揚Lo, YangYangLo2017-03-022018-06-282017-03-022018-06-282016http://ntur.lib.ntu.edu.tw//handle/246246/271897本研究第一部份合成及探討了3種以鋅和二甲基咪唑構成的同質異型性沸石咪唑酯骨架材料：ZIF-8、ZIF-L、dia(Zn)。具有六角型片狀dia(Zn)需要添加甲酸鈉、醋酸、氨水做為催化劑，並在攝氏60度下進行反應；而ZIF-8及ZIF-L在室溫且不需添加催化劑即可合成出來。這說明了合成dia(Zn)的活化能高於ZIF-8及ZIF-L。此外三種晶體以攝氏100度進行了水熱處理以檢測其穩定性：ZIF-8具有最高的水熱穩定性，ZIF-L則具有最低的水熱穩定性。在77K的氮氣吸附檢測中，ZIF-8為孔洞材料；ZIF-L及dia(Zn)則不具有孔洞。但在323.15K的二氧化碳熱重分析中，ZIF-8、ZIF-L及dia(Zn)具有相同數量級的二氧化碳吸附。這顯示了ZIF-L及dia(Zn)的結構會隨著溫度的上升而具有彈性。因此，調整有機金屬骨架的彈性程度是一種有效的方法增加分子分離的效率。 在第二部分的研究提出了一種新穎且可靠的薄膜製備方法：使用了擬多晶形的晶種層，以二維平面材料ZIF-L做為晶種層提供ZIF-8生長，形成ZIF-L@ZIF-8混合薄膜。這個方法使得ZIF-L在薄膜中占有約28%的體積占有率。和傳統的純ZIF-8相比，由於片狀的ZIF-L的使用，使得ZIF-8會沿著晶格<100>的方向生長。在氣體分離的檢測中，ZIF-L@ZIF-8混合薄膜具有較高的氫氣滲透性及氫氣/二氧化碳選擇性。本研究另外使用了有限元素分析分析法進行數值計算，模擬了ZIF-L的擴散係數。我們認為具有層間距的ZIF-L是使得ZIF-L@ZIF-8混合薄膜在氣體分離上有更好的表現的主要原因。This work reports on the synthesis and stability of a polymorphic system of a metal-organic framework (MOF) composed of zinc and 2-methylimidazole, as well as its potential applicability in gas storage/separation. Three polymorphs, ZIF-8, ZIF-L, and dia(Zn) are discussed in this work. It was found that the synthesis of dia(Zn) with a crystal morphology of hexagonal nanosheets requires a catalyst (NH4OH, CH3COOH, or HCOONa), and a synthesis temperature of 60 °C. In contrast, the synthesis of ZIF-8 and ZIF-L can be conducted in the absence of a catalyst and at room temperature. This suggests that the activation energy of dia(Zn) exceeds that of ZIF-8 and ZIF-L. The three crystals were subjected to hydrothermal treatment at 100 °C to evaluate their stability. The ZIF-8 presented the highest hydrothermal stability, whereas ZIF-L presented the lowest. Nitrogen physisorption tests performed at 77K suggests that the microporosity of ZIF-8 exceeds that of ZIF-L and dia(Zn), which were nearly nonporous. Interestingly, CO2 thermogravimetric analysis revealed that the CO2 adsorption of ZIF-L and dia(Zn) at 323.15K is on par with that of ZIF-8, which implies that the flexibility of ZIF-L and dia(Zn) framework increased considerably with temperature. Tuning the flexibility of the framework is another effective approach to the design of new MOF materials for molecular separation. A novel methodology involving the use of pseudopolymorphic seeding for the rational synthesis of highly hydrogen-selective hybrid membranes with a zeolitic imidazolate framework (ZIF) was reported. A proof-of-concept was demonstrated using two-dimensional layered ZIF-L as seed crystals for the growth of its pseudopolymorph ZIF-8 in the formation of ZIF-L@ZIF-8 hybrid membranes. This approach enables the incorporation of ZIF-L (with high hydrogen diffusivity) within the ZIF-8 matrix with a volume fraction of ZIF-L of approximately 28%. Compared with conventional secondary growth methods used in the synthesis of pure ZIF-8 membranes, we employed leaf-like ZIF-L with a high aspect ratio as seed crystals for the growth of ZIF-8 membranes with a preferred orientation along the <100> direction. Compared to pure ZIF-8 membranes, the ZIF-L@ZIF-8 hybrid membranes enable a three-fold enhancement in hydrogen permeability and increase the permeative selectivity of hydrogen-over-carbon dioxide from 2.3 to 4.7. Simulation of mass transfer at the microscopic level was used to elucidate the reasons for the enhanced performance of the membrane in gas separation. We determined that the interlayer spacing among ZIF-L crystals, which allows for the rapid diffusion of hydrogen, is probably the key reason for the high separation performance of the ZIF-L@ZIF-8 hybrid membranes.論文使用權限: 不同意授權有機金屬骨架材料沸石咪唑酯骨架材料同質異型性二氧化碳捕捉及貯存膜分離Metal organic frameworksZeolitic imidazolate frameworkCO2 capture & storagepseudopolymorphismpseudopolymorphic seedingmembrane gas separationthesis10.6342/NTU201602096