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標題: | 開發微流體製程用於水相合成金屬有機骨架及其碳材衍生物在環境之應用 Water-based and Microfluidic Synthesis of Metal-Organic Frameworks and their Carbon Derivates for Environmental Applications |
作者: | 吳希彥 Hsi-Yen Wu |
指導教授: | 吳嘉文 Chia-Wen Wu |
關鍵字: | 微流體,金屬有機骨架,孔洞碳材,奈米碳管,環境保護, Droplet microfluidic system,Metal-organic framework,Porous carbon material,Carbon nanotube,Environmental protection, |
出版年 : | 2022 |
學位: | 博士 |
摘要: | 金屬有機骨架(MOFs)在發明後,受到學術界大量的注目以及研究,因為其高比表面積、可調控的孔徑,對於催化、吸附、氣體分離領域都有重大的潛力。但目前要在工業上應用仍有許多需要克服的困難,主要是因為生產過程困難,且需要批次合成,以及使用大量有機溶劑。對此,我們提出一套新穎的”微流體液滴水相合成系統”來連續快速合成金屬有機骨架。此外,我們利用生質發酵生產酒精後的廢棄沼渣進行碳化造孔,得到的高比表面積多孔碳並進行了多項環境汙染物的移除及捕捉測試,更應用此材料在超級電容器上,以評估此材料的最佳應用。綜合以上金屬有機骨架合成及碳化造孔技術,我們開發一種金屬有機骨架所衍生的包裹奈米碳管之多孔碳材,並透過其優良的導電性進行超級電容器測試。
第一章中,我們將介紹金屬有機骨架及其多孔碳材衍生物,並介紹多種合成方法以及相關文獻的整理。接著介紹本文中所測試的應用,包含了染料移除、金屬離子吸附、二氧化碳捕捉以及超級電容測試。 第二章主要介紹微流體液滴水相合成系統,此系統透過連續式生成ZIF-8以及MIL-100兩種不同的MOFs以取代批次合成,以達到高達50280 kg m-3 g-1的ZIF-8時空產率(space-time yield, STY)。此章中也對於精準控制MOFs合成的溫度及時間進行詳盡的探討,並發現比起批次合成,我們能在此系統中合成時間24秒下,達到批次合成5小時的結晶程度。同時,我們也利用一種新穎的合成方法”原位合成法(de novo approach)”去將異金屬於ZIF-8合成的過程中同步包覆於孔洞結構中,得到Au@ZIF-8。 第三章中,我們將介紹由生質酒精發酵後的稻稈沼渣生質廢棄物進行碳化造孔,所得到的高比表面積多孔碳材(476.05 m2 g-1)在多種應用上的評估。首先我們對染料的移除效率進行評估,得到比擬文獻(217.39 mg g-1)的高移除效率。重金屬吸附我們選用銅離子作為範例,得到高達169.93 mg g-1的高吸附率。二氧化碳的捕捉在0℃下可以得到2.21 mmol g-1的優異表現。最後將此材料應用在超級電容器上測試比電容值,在5 mV s-1得到的比電容值為36.83 F g-1,也跟文獻中所報導的相關生質廢棄物擁有可比擬的數值。 第四章,綜合了上述的MOFs合成技術以及碳化造孔技術,我們提出一種新穎的包裹奈米碳管於MOFs衍生多孔碳材內的方法。首先,合成同時包含Zn及Co的多金屬MOF,並利用原位合成法搭載Ni於MOF中,得到多金屬的MOF(M-ZIF),在高溫鍛燒的過程中,MZIF骨架會崩解,且其配體做為生成奈米碳管的碳源,能使奈米碳管在鍛燒過程中同步生長於MOF的孔洞內(CZIF)。對CZIF進行電性相關測試,能得到在5 mV s-1得到的比電容值為36.83 F g-1,且擁有良好的材料穩定性。 於第五章中,我們對本文的內容進行整理以及總結,同時對文中探討的技術進行未來的前景規劃。 Metal-organic frameworks (MOFs) have received a lot of attention in the academic field in the last decades because of their high specific surface area and regulatory pores offering significant potential for catalysis, adsorption, and gas separation. Furthermore, pyrolysis of MOFs provides a simple approach to obtaining high conductive and porous carbon materials suitable for energy applications such as supercapacitors, novel battery systems, and capacitive deionization. Currently, MOF synthesis is usually conducted with organic solvents in a batch system at elevated temperatures. Although the batch system is simple, low mass and heat transfer, inefficient usage of metal precursors and organic linkers, and the requirement for a large number of organic solvents are disadvantages that need to be improved with respect to mass production for practical applications. In this Ph.D. dissertation, two novel MOF synthesis techniques are developed. The first technique is a water-based droplet microfluidic technique for continuous MOF synthesis to solve the mass production problems encountered in conventional batch systems with organic solvents. The second technique is the de novo synthesis of multi-metal MOFs followed by their subsequent pyrolysis to obtain porous carbon materials with carbon nanotube inside their web structure for electrochemical applications. Both developed techniques have a significant impact on MOFs practical application. In Chapter 1, the basic structure, properties, and variety of synthetic methods of MOFs and MOF-derived porous carbon materials are introduced as well as their applications tested in this dissertation including dye removal, metal ion adsorption, carbon dioxide capture, and supercapacitor. In Chapter 2, a water-based droplet microfluidic system is introduced for the continuous synthesis of three kinds of MOFs including ZIF-8, MIL-100, and Au@ZIF-8. A plot regarding the water flow rate versus the oil flow rate of this two-phase droplet system is established to understand the relative water and oil flow rate range for the generation of the stable droplet. ZIF-8 and MIL-100 are synthesized first to compare the difference between the droplet microfluidic system and the batch system as well as the key advantages of the former. Based on SEM and XRD analysis, a droplet microfluidic system can generate MOFs with narrower size distribution and better crystallinity in a shorter time and at lower temperatures. The droplet microfluidic system is further tested for the synthesis of gold particles embedded in the structure of ZIF-8 via the de novo approach. Compared with the conventional incipient wetness impregnation approach, the de novo approach offers efficient usage of gold precursors as indicated by the high gold signal inside ZIF-8 as shown in SEM-EDX analysis. In Chapter 3, biomass residue from the acid-catalyzed steam explosion of rice straw followed by anaerobic fermentation is used as carbon precursors for the synthesis of biomass-derived porous carbon materials via carbonization and KOH-activation process. The BET specific surface area of biomass-derived porous carbon material is 476.5 m2 g-1, which is much higher than the original biomass residue (4.8 m2 g-1). Three applications are tested to show the practical applications of the porous carbon material including methylene blue dye removal, copper ion removal, and CO2 capture. All three cases show comparable adsorption and absorption behavior to other biomass-derived carbon materials. In addition, the specific capacitance is measured and a value of 36.83 F g-1 at 5 mV s-1 indicates the potential of the biomass-derived porous carbon materials as supercapacitance material for energy storage. In Chapter 4, de novo synthesis of multi-metal MOFs combined with pyrolysis to obtain porous carbon materials with carbon nanotubes (CNT) inside the web structure is developed based on the techniques established in the previous two chapters. Three metal ions including Co2+, Zn2+, and Ni2+ are used as metal precursors, while 2- methylimidazole is used as organic linkers for MOF synthesis. The main structure of the resulting multi-MOFs is ZIF-8 (Zn2+) accompanied by some ZIF-67 (Co2+) and Ni ion precursor inside. Ni ions are reduced to Ni nanoparticles during pyrolysis, and porous carbon materials with embedded nickel nanoparticles attached by carbon nanotubes are formed. BET specific surface area of the resulting porous carbon is around 246.36 m2 g-1 when pyrolysis at 600oC. The organic linkers provide a carbon source for CNT growing while Ni nanoparticles act as CNT growing catalysts. The electrochemical measurement at 5 mV s-1 is performed as well, and a value of 36.83 F g-1 indicates the porous carbon materials with CNT inside have the potential for energy application. In Chapter 5, the experimental results of Chapter 2~4 are summarized and the prospects of these two developed MOF-related techniques, water-based droplet microfluidic technique for continuous MOF synthesis and de novo synthesis of multi-metal MOFs combined with pyrolysis for porous carbon materials with carbon nanotube will be discussed as well. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/91986 |
DOI: | 10.6342/NTU202201426 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 綠色永續材料與精密元件博士學位學程 |
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