金屬有機框架催化生物質高值化反應: 觸媒設計與反應機制探討

Catalytic Biomass Conversion over Metal-Organic Frameworks (MOFs): Catalysts Design and Reaction Mechanism Investigation

葉俊毅(Jyun-Yi Yeh)

指導教授 ： 吳嘉文

國立臺灣大學/工學院/分子科學與技術國際研究生博士學位學程/博士(2022年)

https://doi.org/10.6342/NTU202201213

摘要

金屬有機框架(MOFs)與MOFs衍伸觸媒具有之高效與高選擇性，可用作催化生物質轉換反應。透過生物質轉換反應，生物質廢棄物被轉化為可替代石化產品之高單價化學品(生物質高值化)，進而減低日常生活對石化來源之依賴性，並同時解決生物廢棄物處理之能源消耗與環境汙染問題。因此，我們利用MOFs與其衍生材料發展生物質高值化反應，並進一步透過密度泛函理論(DFT)計算推敲其反應背後之機制與原理。第一部分中，我們利用同步合成手法，於Al-MOFs長晶時嵌入鉑，透過燒結與還原，可合成一高效MOFs衍生氧化鋁支撐式鉑觸媒(Pt@Al2O3)，用於催化液相氫源(NaBH4)輔助觸發之糠醛氫化開環反應以產出高產率之1,5-戊二醇(75%)且無任何1,2-戊二醇副產物產生。Pt@Al2O3相較於含浸法合成之Pt/γ-Al2O3觸媒具有較高之1,5-戊二醇產率與較高之Pt分散性，透過鋁固態核磁共振與X射線光電子能譜儀，我們發現Pt@Al2O3中之五配位Al3+ 可以透過Pt-O-Al鍵結形成強金屬-載體交互作用，進而分散Pt於氧化鋁載體上。而透過同位素標記法與DFT模擬，我們發現NaBH4氫解之鹽類(NaBO2)會抑制1,2-戊二醇生成進而提升主產物1,5-戊二醇之產率。
第二部分中，我們發現硼氫化合物與釕奈米觸媒之協同效應可有效於甲醇環境下催化二糠基亞胺(difurfuylimine)之氫化反應。使用MIL-53-NH2(Ru,Al)衍生氧化鋁支撐式釕觸媒與硼烷胺錯合物(NH3BH3)於80 ºC、花費一個小時可得92%之二糠基胺產率。密度泛函理論(DFT)計算顯示甲醇胺(NH4OCH3)、氫氣分子與二糠基亞胺之亞胺鍵可形成五元還之反應過度態，並進而降低反應的活化能。
於第三部份中，一非貴金屬雙觸媒反應系統(P-UiO-66 + Ni-Co@NC)被開發並應用於一鍋轉化(one-pot conversion)醣類至2,5-二甲基呋喃。利用此雙觸媒系統，果糖與葡萄糖可於160 ºC、8小時、7大氣壓氫氣與THF/water雙溶劑條件下被轉化成產率85.2%與82.1%之2,5-二甲基呋喃。
在第四部分中，我們開發一異相鉍金屬有機框架觸媒(Bi-BTC)用於催化2,5-二甲基呋喃與丙烯酸之狄耳士-阿爾德反應並產生92%產率之對二甲苯，透過DFT計算，Bi-BTC的特殊Bi活性點結構可提升狄耳士-阿爾德反應中間體之選擇性，進而產生較氧化鉍更高之狄耳士-阿爾德反應產物。
於第五部份中，我們開發一應用於QM/MM模型之DFT參數組合。此參數組可以描述多種吸附於Zr-MOFs化合物之吸附能，亦可有效重現Zr-MOFs催化之葡萄糖異構化、差向異構化與糠醛之催化轉移氫化反應之活化能。
結合上述之結果與技術(材料合成、材料鑑定、觸媒化學與DFT模擬)，我們得以研究MOF的孔洞大小對反應機制影響之研究。第六部分中，我們調控有機配體長短與種類，合成一系列有不同孔洞大小、孔洞形狀之單一活性點位觸媒(Co-MOF-808、Co-NU-1200、Co-NUS-8)。實驗結果顯示，Co-MOF-808與Co-NU-1200觸媒可以將糠醛加氫脫水成≥99%產率之2-甲基呋喃，而使用2D MOF觸媒(Co-NUS-8)轉化糠醛則以氫化開環之1,2-戊二醇為主產物。於反應物與產物之擴散測試中，可以發現，一般認為MOF之孔洞透過調控反應物與產物擴散速率而造成產物產率不同之概念並不適用於此反應。然而我們使用QM/MM模擬發現，MOF的孔洞可以藉由控制Transition state geometries，進而調整反應路徑方向與控制各產物之選擇率

關鍵字

金屬有機框架

並列摘要

Metal-organic frameworks and their derived materials are featured for efficient and selective catalytic performance; therefore, they can be utilized in biomass valorization. Through biomass valorization, biomass waste is converted into high-value chemicals. These valuable compounds can serve as alternatives for petroleum-derived chemicals and further decrease the petroleum demand in daily life. Meanwhile, biomass conversion can reduce the pollution and energy consumption caused by the biomass waste treatment. Therefore, we utilize the MOFs and MOF-derived catalysts in biomass valorization. Furthermore, with density functional theory (DFT) calculations, we can investigate the mechanism behind the reactions further.
In the first section, we reported a selective conversion of furan aldehydes and alcohols to polyols over MOF-derived alumina-supported platinum catalyst (Pt@Al2O3) through an α-C−O bond hydrogenolysis process under mild reaction conditions (45 ºC, aqueous media). The Pt@Al2O3 was dervied from in situ prepared Pt-embedded metal-organic frameworks (i.e., MIL-53(Al)-NH2). The high yield of 75% 1,5-pentanediol (1,5-PD) can be achieved. As revealed by density functional theory (DFT) simulations, sodium borohydride (NaBH4) acts as both a hydrogen donor and a essential role in an exclusive α-C−O bond cleavage by mediating the hydrogenolysis pathway as revealed by the DFT calculations.
In the second section, we displays an reductive amination of FAL over alumina-supported Ru catalyst derived from MIL-53-NH2(Ru, Al) with ammonia borane (NH3BH3) as the reducing agent. 92% yield of DiFAM can be reached in 1 h at 80˚C. Density functional theory calculations suggested that the ammonia methoxide (NH4OCH3) would form a five-membered ring transition state with hydrogen and the imine bond of DiFIM, which reduced the activation energy of the hydrogenation of DiFIM.
In the third section, we report the P-UiO-66 and Ni-Co@NC noble-metal free co-catalysts for the efficient DMF production from saccharides using a one-pot process. The high DMF yield achieved 85.2% and 82.1% for fructose and glucose, respectively, at 160 ºC in 8 h using THF/water as the bi-phasic solvent, under 0.7 MPa H2 pressure.
In the fourth section, a heterogeneous Bi-BTC was synthesized for Diels-Alder conversion of bio-based 2,5-dimethylfuran and acrylic acid. A high yield (92%) of para-xylene can be achieved by the utilization of Bui-BTC under 160 ºC, 10 bar with low reaction energy barrier (47.3 kJ/mol). The DFT calculation proposed reaction the unique Bi3+ active site structure demonstrated remarkable Diel-Alder catalytic performance.
In the fifth section, a set of charge and Lennard-Jones parameters is derived for electrostatically embedded QM/MM calculations to model adsorptions and reactions occurring in Zr-MOFs. With this set of parameters, the binding energies calculated with QM/MM meet the experimental adsorption energies with an RMS error of 0.6 kcal/mol for a diverse set of adsorbates in two different Zr-MOFs (UiO-66 and MOF-808), suggesting that the MM parameters can properly capture long-range Coulombic and van der Waals interactions in these systems. Activation energies of glucose isomerization, and epimerization are also calculated using the QM/MM model and the calculations reproduce the experimental values to within 0.6 kcal/mol.
In the final sections, we demonstrate the transition state control of single-site Metal-Organic Framework Catalysts on pore shape and size selective hydrogen-involved reactions. We synthesized three Co-single site MOFs with different porous structures (Co-MOF-808, Co-NU-1200, and Co-NUS-8) for furfuryl alcohol (FOL) hydrodeoxygenation and ring-opening hydrogenolysis. By advanced quantum mechanics/molecular mechanics (QM/MM) simulations, we present the crucial role of transition control in FOL hydrogen-involved reactions over Co-single site Zr-MOF catalysts. The results display that the 3D porous Zr-MOF frameworks result in lower activation energy and higher selectivity of the hydrodeoxygenation of FOL (Yield = ≥99% 2-methylfuran (2-MF)). On the contrary, the 2D NUS-8 structure contributes to lower barrier and larger selectivity of FOL to 1,2-pentanediol (1,2-PD) reactions (Yield = 88% 1,2-PD 12% 2-MF). In addition, the indistinguishable diffusion rate difference of FOL, 2-MF, and 1,2-PD on each MOF reaffirm the critical part in the regulation of product selectivity.

並列關鍵字

Metal-Organic Framework

參考文獻

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