| 摘要: | 目前全球氣候變遷議題已成為最嚴峻且迫切需要解決的環境問題，其中甲烷（CH₄）作為全球暖化潛勢（GWP）達二氧化碳（CO₂）25倍的第二大溫室氣體，其減排與資源化技術已被視為重要的短期策略目標。目前甲烷氣體處理方式大多偏向氣體回收後燃燒（如鍋爐燃料使用），雖可消除甲烷直接排放，但最終仍轉化為二氧化碳排放，未能根本解決碳循環問題。若能將甲烷有效轉化為具有經濟價值之有機化合物，將有助於實現永續碳循環與能源價值提升。
本研究採用金屬有機框架（Metal-Organic Framework, MOF）作為低溫水相氧化甲烷的觸媒平台，分別選用 Cu-Zr-MOF808 與 Cu-Ce-MOF808 進行反應性測試。實驗設計中於密閉厭氧瓶中注入7 mL純甲烷與1 mL超純水，加入5 mg MOF觸媒後於150°C條件下反應12小時，並使用GC-FID進行液相產物分析。
實驗結果顯示，Cu-Zr-MOF808 在反應後產生 31.8 ppm 的乙酸甲酯，而 Cu-Ce-MOF808 則檢測到 84.5 ppm 的乙酸，不添加純甲烷對照組則無產物生成。依據文獻理論與本實驗之分析，Cu-Zr-MOF808觸媒催化甲烷反應路徑推論為甲烷首先氧化生成甲醇，隨後氧化為乙酸，並在觸媒表面 Lewis 酸位點催化下進一步酯化生成乙酸甲酯。另外Cu-Ce-MOF808觸媒催化甲烷反應路徑推論為甲烷一步氧化生成乙酸，是藉由Ce³⁺/Ce⁴⁺氧化還原循環及孔道效應來催化反應。對於轉化率與選擇性計算，因分析儀器限制，僅推估甲烷反應消耗的濃度曲線下，所對應目標物的選擇性。
本研究驗證 MOF 觸媒在低溫、水相、微量氧氣條件下對甲烷具備選擇性氧化潛力，並呈現 Cu-Zr-MOF808與Cu-Ce-MOF808兩種MOF觸媒的不同反應路徑與催化特性。研究成果不僅提供甲烷轉化為液態含氧有機物的可行性依據，亦為未來甲烷減排與資源化利用技術開發提供理論支撐與實務參考。
;Global climate change has become one of the most critical and pressing environmental issues in the world today. Methane (CH₄), as the second most significant greenhouse gas (GHG) with a global warming potential (GWP) approximately 25 times greater than that of carbon dioxide (CO₂), has attracted increasing attention. The development of reduction and valorization technologies for methane is regarded as a key short-term strategy. Currently, most methane mitigation approaches focus on combustion for energy recovery (e.g., as boiler fuel). While such methods eliminate direct methane emissions, they ultimately result in CO₂ emissions, failing to address the core issue of carbon circularity. Converting methane into value-added oxygenated organic compounds offers a promising pathway toward sustainable carbon recycling and enhanced energy utilization.
This study employed Metal–Organic Frameworks (MOF) as catalytic platforms for the aqueous-phase oxidation of methane under low-temperature conditions. Cu-Zr-MOF808 and Cu-Ce-MOF808 were selected as catalysts for activity evaluation. The experimental setup involved injecting 7 mL of pure methane and 1 mL of ultrapure water into a sealed anaerobic vial, followed by the addition of 5 mg of MOF catalyst. The reaction was conducted at 150 °C for 12 hours, and the liquid-phase products were analyzed using gas chromatography with a flame ionization detector (GC-FID).
The results revealed that Cu-Zr-MOF808 produced 31.8 ppm of methyl acetate, while Cu-Ce-MOF808 yielded 84.5 ppm of acetic acid. No products were detected in the control group without methane, indicating that methane is the critical reactant. Based on literature and experimental analysis, the proposed reaction pathway for Cu-Zr-MOF808 involves sequential oxidation of methane to methanol and then to acetic acid, followed by esterification on Lewis acid sites of the MOF surface to form methyl acetate. For Cu-Ce-MOF808, the reaction pathway is proposed as one-step oxidation of methane to acetic acid, facilitated by Ce³⁺/Ce⁴⁺ redox cycling and pore confinement effects. Due to limitations in instrumental capabilities, the conversion and selectivity were estimated based on simulated methane consumption scenarios.
This study confirms the potential of MOF catalysts to selectively oxidize methane under low-temperature, aqueous-phase, and oxygen-limited conditions. The distinct catalytic behaviors and mechanistic pathways of Cu-Zr-MOF808 and Cu-Ce-MOF808 are elucidated, offering feasible routes for converting methane into oxygenated liquid chemicals. These findings provide both theoretical insight and practical references for the future development of methane abatement and resource utilization technologies. |
