伴隨全球能源危機與淨零碳排趨勢，發展潔淨且可再生之能源已成為永續發展的重要課題。氫氣因具有高能量密度且使用後產物為水等優點，被視為極具潛力的綠色能源載體。其中，光催化水分解技術可直接將太陽能轉換為化學能，為具發展潛力的產氫途徑。金屬有機框架（Metal-Organic Framework， MOF）因具有高比表面積、可調控孔洞結構及明確金屬活性位點，近年來已成為新興的光催化材料。然而，水分子於材料表面的吸附與後續 O–H 鍵活化仍是影響水分解效率的重要因素。因此，本研究透過密度泛函理論（Density Functional Theory， DFT）計算，探討金屬有機框架材料之電子結構、水分子吸附行為與水解離反應機制，並進一步分析金屬摻雜對材料表面反應活性的影響。 本論文第一部分以鋅基金屬有機框架(Zn-MOF， [Zn(2-mna)₂]n ) (2-mma = 2頸菸酸根) 作為主要研究對象，並探討不同 Cu 摻雜濃度對其結構穩定性與電子結構之影響。形成能結果顯示，當 Cu 摻雜濃度為 12.5 % 至 37.5 % 時，系統具有負形成能，代表此濃度範圍下之摻雜結構在熱力學上相對穩定。進一步由態密度與部分態密度分析可知，Cu 摻雜後會於導帶底部引入新的電子態，顯示 Cu 摻雜可有效調控材料局部電子結構，並可能改變材料與吸附分子之間的交互作用。 在水分子吸附行為方面，原始 Zn-MOF 之 Zn 點位對水分子具有較佳的初始吸附能力，其吸附能為 -0.419 eV；而 37.5 % Cu 摻雜 Zn-MOF 之 Cu 點位吸附能為 -0.284 eV，顯示 Cu 摻雜後並未明顯提升水分子的初始吸附能力。然而，透過電荷密度差分圖與 Mulliken 電荷分析可觀察到，水分子吸附後材料表面產生明顯電子重新分布，表示水分子與 MOF 表面之間仍存在交互作用。進一步透過吉布斯自由能與過渡態搜尋分析水分子解離反應，結果顯示，當水分子初始吸附於 37.5 % Cu 摻雜 Zn-MOF 之 Cu 點位時，水解離反應活化能障可由原始 Zn-MOF 之 Zn 點位的 1.43 eV 降低至 0.05 eV，代表 Cu 點位可有效降低水分子 O–H 鍵斷裂所需跨越的能量限制，使水分子解離在動力學上更容易進行。因此，Cu 摻雜雖未直接增強水分子初始吸附能力，但可透過改變局部電子結構促進水分子活化與解離反應。 本論文第二部分則建立銀基金屬有機框架 Ag-MOF 模型，並透過模擬 XRD 圖譜與實驗結果比對，驗證所建立結構之可靠性。能帶結構分析顯示，Ag-MOF 具有 2.127 eV 的直接能隙，屬於半導體材料。進一步由態密度與部分態密度分析可知，Ag-MOF 之價帶頂主要由 S 3p 軌域貢獻，而導帶底則主要由 C 2p 軌域貢獻。透過 BFDH 理論與晶面暴露情形分析後，選擇可有效暴露 Ag 金屬點位之 (1 -1 0) 晶面進行後續水分子吸附模擬。結果顯示，水分子於 Ag 點位之吸附能為 -0.381 eV，表示 Ag-MOF 對水分子具有中等程度的吸附能力。電荷密度差分圖與 Mulliken 電荷分析亦顯示，水分子吸附後會造成表面局部電子密度重新分布，說明 Ag 點位與鄰近配體環境會共同影響水分子吸附行為。 綜合以上結果，本研究證實金屬中心與異質金屬摻雜可有效調控 MOF 之電子結構與表面反應行為。其中，Cu 摻雜 Zn-MOF 雖未提升水分子初始吸附能力，但能明顯降低水分子解離反應之活化能障；而 Ag-MOF 則展現半導體特性與中等水吸附能力。此研究結果可作為未來設計與開發 MOF 光催化水分解材料之理論基礎。;With the global energy demands and the requirement of net-zero carbon emissions， the development of clean energy has become an important issue for further application. Hydrogen is regarded as a promising green energy carrier because of its high energy density and environmentally friendly. Among various hydrogen production technologies， photocatalytic water splitting can directly convert solar energy into chemical fuels and is therefore considered as a potential approach for hydrogen production. Metal-organic frameworks (MOFs)， which possess high specific surface areas values， tunable pore structures， and well-defined metal active sites， have emerged as promising photocatalytic materials in recent years. However， the adsorption and reaction kinetics of water molecules on material surfaces remain important factors affecting water splitting efficiency. Therefore， the density functional theory (DFT) calculations were performed to investigate the electronic structures， water adsorption behaviors， and water dissociation mechanisms of MOF materials. The effect of Cu ions doping on the surface reactivity of MOFs was further analyzed. The first part of this study focuses on the zinc-based metal-organic framework [Zn(2-mna)]n (2mna = 2-mercaptonicotinate) and investigates the effects of various concentrations of Cu doping on their structural stabilities and electronic structures. Their calculated formation energy results show that samples with concentrations of Cu doping in the range of 12.5 % to 37.5 % exhibit negative formation energies， indicating that the Cu-doped into samples in this range are relatively thermodynamically stable. Furthermore， density of states and partial density of states analyses reveal that Cu doping generates new electronic states at the bottom of the conduction band. This result suggests that Cu doping can effectively regulate the local electronic structure of Zn-MOF and may alter the interaction between the material and adsorbed molecules. In analysis of water adsorption behavior， the Zn sites of pristine Zn-MOF shows better initial water adsorption ability， with an adsorption energy of -0.419 eV. In comparison， the Cu sites for the 37.5 % Cu-doped Zn-MOF sample exhibits an adsorption energy of -0.284 eV， indicating that Cu doping might not significantly enhance the adsorption ability of water molecules. However， charge density difference and Mulliken charge analyses show that water adsorption induces obvious electron redistribution on the material surface， suggesting that interactions still influence water molecules and the MOF surface. Furthermore， Gibbs free energy and transition state analysis were performed to evaluate the water dissociation reaction. The results show that when water is adsorbed at the Cu site at 37.5 % Cu-doped Zn-MOF， its activation energy barrier for water dissociation decreases to 0.05 eV compared with the Zn site of pristine Zn-MOF， indicating that the Cu site can effectively reduce the energy barrier for O–H bond cleavage， and making high water dissociation. Therefore， although Cu doping does not directly enhance the initial adsorption of water molecules， it promotes water activation and dissociation by tuning the local electronic structure and lowering the activation energy barrier. The second part of this study focuses on the construction of a silver-based metal-organic framework， Ag-MOF. The reliability of the established structure was verified by comparing the simulated X-ray diffraction pattern with the experimental result. The band structure analysis shows that Ag-MOF has a direct band gap of 2.127 eV and exhibits semiconducting behavior. Further density of states and partial density of states analyses indicate that the valence band maximum of Ag-MOF is mainly contributed by S 3p orbitals， while the conduction band minimum is mainly contributed by C 2p orbitals. Based on BFDH theory and surface exposure analysis， the (1 -1 0) surface was selected for subsequent water adsorption simulations because it is suitable for water absorption. The results show that the adsorption energy of water on the Ag site is -0.381 eV， indicating that Ag-MOF exhibits moderate adsorption ability toward water molecules. Charge density difference and Mulliken charge analyses also reveal that water adsorption causes local electron density redistribution on the surface， suggesting that both the Ag site and the neighboring ligand environment influence the water adsorption behavior. Overall， this study demonstrates that metal centers and heterometal doping can effectively regulate the electronic structures and surface reaction behaviors of MOFs. Cu-doped Zn-MOF does not enhance the adsorption ability of water molecules but significantly lowers the activation energy barrier for water dissociation. Meanwhile， Ag-MOF exhibits semiconducting characteristics and moderate water adsorption ability. These results provide a theoretical basis for the future design and development of MOF-based photocatalytic water splitting materials.
