| 摘要: | 本篇論文分成兩部分：
二氧化碳（Carbon dioxide, CO2）大量排放，已成為導致全球暖化及溫室效應日益嚴重的主要原因之一。為減緩氣候變遷影響，如何有效捕捉與轉化二氧化碳成為當前研究的重點課題。目前工業上普遍使用的二氧化碳吸附劑如單乙醇胺（Monoethanolamine, MEA）和三乙醇胺（Triethanolamine, TEA），雖然具備一定的吸附效果，但因其再生能耗高、腐蝕性強及環境友善性不足等缺點，限制了其實際應用。
近年來，金屬有機骨架材料（Metal-Organic Frameworks, MOFs）因其高比表面積及孔洞可調性，成為具有潛力的新興二氧化碳吸附材料。在眾多的MOFs材料中，MOF-74具有一維孔洞結構和未配位的活性位點，能與二氧化碳形成較強的相互作用，進而增強吸附和擴散效率。然而，單純的物理吸附難以實現高效的利用。因此引入酶催化轉化的概念，將甲酸脫氫酶（Formate Dehydrogenase, FDH）結合MOF-74，形成一種生物複合材料不僅能有效吸附二氧化碳，還能催化二氧化碳還原生成具經濟價值的甲酸。
本研究中參考本實驗室於2015年基於酵素固定化概念，研發出創新的原位溫和水相合成法，成功將過氧化氫酶（Catalase, CAT）封裝於ZIF-90中。透過MOF孔洞結構，使基質順利進入催化位點，同時防止大分子蛋白酶的水解作用，提升酵素穩定性與活性。2021年，本實驗室進一步改良技術，於室溫下以溫和水相系統快速合成Zn-MOF-74並同時封裝酵素，顯著提升固定化酵素的活性。在此基礎上進一步將甲酸脫氫酶封裝於Zn-MOF-74中，利用其優異的二氧化碳吸附能力及14 Å大孔道結構，增加菸鹼醯胺腺嘌呤二核苷酸（Nicotinamide adenine dinucleotide, NADH）與二氧化碳的擴散能力，提升二氧化碳還原成甲酸的效率。為進一步增強吸附性能，將金屬中心由Zn改為Co，並也成功把酵素封裝於Co-MOF-74之中，因其Co²⁺具有空的3d軌道，能夠更容易與CO₂形成配位，進一步加強CO₂的吸附。有效增強二氧化碳捕集及催化轉化效率。實驗結果顯示，甲酸脫氫酶和Co-MOF-74組成的複合生物材料在CO₂吸附及甲酸生成上，均優於Zn-MOF-74，展現其在溫室氣體轉化應用中的潛力。
本論文第二部分著重於開發一套具高效率與通用性的機械力輔助封裝技術(Mechanochemical, LAG) ，成功將奈米金屬粒子封裝於金屬有機框架中，實現特定尺寸與晶面之奈米金屬催化劑的快速製備。傳統奈米金屬因具高表面能，極易在反應過程中發生團聚與粒徑成長，進而導致催化活性下降與回收困難。本研究藉由MOFs具備高度有序孔洞與框架結構的特性，不僅有效隔離金屬奈米粒子、抑制其團聚，亦大幅提升其結構穩定性與重複使用能力。考量不同晶面在催化選擇性與反應活性上所展現之顯著差異，本研究進一步採用球磨法成功封裝具特定晶面之奈米金屬，並透過MOFs提供的保護環境，在高溫或酸性等嚴苛條件下仍可維持其原始晶面結構，保留其優異的催化功能。而且MOF材料所具有之分子篩選性孔徑亦有助於反應物選擇性進入，有效提升催化反應之產率與選擇性。
與傳統合成方法水熱合成需24小時或是兩步驟球磨程序耗時約6.5小時相比，本研究所建立之封裝方法具備顯著的時間與流程優勢，可於單一步驟且僅需約5分鐘內完成奈米金屬與MOF前驅物的反應與包覆過程。此策略大幅簡化操作流程並提高反應效率，展現其作為快速、穩定且可控制製備異相奈米催化劑平台的可行性與實用潛力。
;This thesis is divided into two main parts:
Massive CO₂ emissions are a major driver of global warming and the greenhouse effect. To address climate change, efficient CO₂ capture and conversion have become a research priority. While industrial absorbents like monoethanolamine (MEA) and triethanolamine (TEA) are effective, they suffer from high regeneration costs, corrosiveness, and poor environmental compatibility.
Metal-Organic Frameworks (MOFs), particularly MOF-74, offer promising alternatives due to their high surface area, tunable pores, and unsaturated metal sites that enhance CO₂ adsorption and diffusion. However, physical adsorption alone limits practical utility. To increase CO₂’s value, this study integrates formate dehydrogenase (FDH) with MOF-74 to form a bio-composite that not only captures CO₂ but also catalyzes its reduction to formic acid—a commercially valuable product.
In 2015, we reported an innovative in situ method to encapsulate catalase (CAT) within ZIF-90 under mild, aqueous, room-temperature conditions. The porous MOF structure permitted substrate access while protecting the enzyme from hydrolysis, enhancing stability and activity. In 2021, we refined this approach to rapidly synthesize Zn-MOF-74 under similar conditions, enabling simultaneous enzyme encapsulation and significantly improving catalytic performance.
Building on our 2015 study, we encapsulated formate dehydrogenase (FDH) into Zn-MOF-74. Its strong CO₂ adsorption and 14 Å channels enhanced the diffusion of NADH and CO₂, improving formic acid production. To further boost adsorption, Zn was replaced with Co, and FDH was successfully encapsulated into Co-MOF-74. The Co²⁺ ions, with empty 3d orbitals, provided stronger CO₂ coordination. As a result, the FDH@Co-MOF-74 bio-composite outperformed the Zn-based counterpart in both CO₂ capture and conversion, showing strong potential for greenhouse gas mitigation.
The second part of this study presents a rapid and versatile mechanochemical strategy for synthesizing MOF-based nanocomposites containing metal nanoparticles (NPs) with controlled sizes and exposed crystal facets. Metal NPs typically suffer from aggregation due to high surface energy, reducing catalytic activity and complicating recovery. Utilizing the ordered porous structure of MOFs, this method prevents NP aggregation and enhances their stability and reusability.
Recognizing the importance of crystal facets in catalytic performance, facet-controlled NPs were encapsulated via ball milling. The MOF framework protects these facets under harsh conditions (e.g., high temperature, acidity), preserving catalytic activity. Additionally, the molecular sieving effect of MOFs improves substrate selectivity by controlling reactant diffusion.
Compared to conventional hydrothermal (24 h) or two-step milling (6.5 h) methods, this one-step encapsulation completes in just 5 minutes, offering significant advantages in speed and simplicity. This strategy provides a robust, efficient, and scalable platform for fabricating heterogeneous catalysts. |
