| 摘要: | 近年來，對於金屬有機骨架材料(Metal-organic Frameworks) 的研究獲得相當大的重視。其優秀的孔洞選擇性(pore selectivity)、高比表面積(surface area)、以及較大的內部孔徑，在氣體儲存、分子篩選、反應催化、以及藥物載體上，皆有良好的表現。而其中，以鋯氧配位所形成之金屬有機骨架材料，更是以其優異的熱化穩定性(thermal stability)，受到諸多的關注。因此，許多實驗室皆不斷開發以鋯為金屬源的骨架材料，其中以對苯二甲酸(Terephthalic acid, BDC) 為有機配位體的UiO-66(Universitetet i Oslo-66)最受關注。然而，傳統合成金屬骨架材料的方法以熱溶劑法 (solvothermal) 為主，往往需要耗費大量的時間、溶劑、以及高溫的環境。因此本實驗室在2017年時以機械力化學的方式，以微量的溶劑以及時間，於室溫之下合成出了UiO-66-F4 (將苯環上的氫以氟取代)，以及其不同官能基的衍生物。此外，我希望可以根據熱溶劑法的機制，推測出機械力化學法的反應機制，並應用在更多的骨架材料之上。除了UiO-66之外，以聯苯二甲酸(Biphenyl-4,4′-dicarboxylic acid BPDC) 為有機配位體的UiO-67；以及以反丁烯二酸(fumaric acid) 為有機配位體的MOF-801皆是以鋯氧鍵形成的骨架材料。而三種不同的有機配位體在利用機械力化學法合成時，皆適合不同的合成環境，藉由調控酸鹼、有機溶劑、以及反應時間等，可得到更為良好的產物。因此，本實驗將以不同的反應環境來快速合成有機金屬骨架材料，已達到綠色化學的目的。同時測試在不同酸鹼的環境下，有機金屬骨架材料是否得以快速成形，以建立之後進行相關實驗時所需要的資料與經驗。;Metal-organic Frameworks (MOFs) are one of the most exciting classes of chemical structures to be discovered in the past decade. Because of their high surface area and thermal stability, MOFs has great behavior in catalysis, drug delivery, gas storage, and molecular separation. MOFs consist of metal nodes and organic linkers, which are connected by coordinate bond. Electrons provided from organic linkers will occupy the empty orbitals from metal atoms to form a strong covalent bond. Especially the MOFs contain zirconium-oxygen bonds, exhibit outstanding thermal and chemical stability. For example, UiO-66, UiO-67, MOF-801, are composed by zirconium cluster and dicarboxylic acid, such as terephthalic acid, biphenyl-4,4′-dicarboxylic acid, and fumaric acid, exhibit excellent thermal and chemical stabilities. However, conventional methods for obtaining MOF materials require a lot of time, organic solvent under high temperatures. Due to our lab utilizes mechanochemistry to synthesize UiO-66-F4 in short time and reduce the solvent cost dramatically. With this concept, we try to synthesize more and more MOFs by this method, meanwhile, the derives of UiO-66 are our first target.
To synthesize MOFs with mechanochemistry, the metal reactant must be changed. Traditionally, we synthesize MOFs with metal salts such as ZrCl4, and ZrOCl2. These metal salts easily dissolve into the organic solvent such as dimethylformamide (DMF) and Dimethylsulfoxide (DMSO). However, when the reactants in the reaction grinding can, there is only little solvent inside, so we have to use zirconium cluster to synthesize the zirconium organic frameworks. Zirconium clusters are synthesized with zirconium propoxide and monoprotic acids such as methacrylic acid and acetic acid. These two clusters are used in my experiments and I successfully synthesize UiO-66 and UiO-67 with these clusters. However, the mechanism of mechanochemistry is the key point we wonder. So I synthesize zirconium-MOFs with different conditions, I changed pH values, solvent volumes, and clusters, to figure out what make MOFs crystallized successfully in the reaction. At last, I found that suitable reaction speed is the key point to synthesize the MOFs. In the basic condition, the dissociation of organic linkers will be too fast to form crystal structures, most reactants will form the amorphous products. In contrast, when the organic linkers in acidic environments the proton will not dissociate easily, and the reaction will not progress, neither. In the end, we exploit this concept to synthesize MOF-801 with mechanochemistry successfully and hope the experiences can be utilized in the future. |
