仿生性釕基氫團簇之合成及其光催化產氫之應用研究

Abstract

氫氣是一種乾淨無汙染並被視為可以替代石化燃料的再生性能源。在自然界中，氫化酶(Hydrogenase)可藉由催化氫分子與氫質子間的可逆氧化還原反應(2H+ + 2e- ↔ H2)來產生氫氣。鐵-鐵產氫酶([FeFe] hydrogenase)活性區的氫簇分子(H-cluster)為氫氣產生的催化中心，其結構為一個雙硫架橋雙鐵錯合物，常作為仿生性光催化劑並被應用於光催化產氫上。因此我們的目標在於模擬鐵-鐵產氫酶活性中心–氫簇分子的化學結構，置換其中心的鐵金屬為釕金屬，以合成仿生性釕基氫團簇。在此論文中我們成功合成出[Ru2(CO)6(-S(CH2)3S)] 及[(Ru3(CO)10)2(-S(CH2)3S)]，並藉由核磁共振光譜儀(NMR)、質譜儀(MS)、傅立葉轉換紅外線光譜儀(FT-IR)及X-光單晶繞射儀(Single Crystal X-ray)進行結構鑑定及分析。此外，兩種不同質子來源(水及甲酸)的系統(水相/有機相)被利用來探討這些仿生性釕基氫團簇產氫的光催化活性，並進一步的外加一系列具有不同推拉電子特性的磷化合物於光催化系統中來探討其對產氫效率的影響。結果顯示，在氫氣產生效率的比較上，在甲酸系統(有機相)下的產氫效率比水(水相)來的高。而有機相中，在磷化合物的添加下，仿生性釕基氫團簇皆顯示了高效率的產氫活性，且具有推電子官能基的磷化合物對產氫效率的影響高於拉電子官能基的磷化合物；其中又以[Ru3(CO)10]2[-S(CH2)3S]在三(四-甲氧苯基)磷(P(p-C6H4OMe)3)的添加及500瓦氙燈的照射下能觀察到最好的產氫效率，其氫氣轉換的效率–每小時每莫耳化合物催化每莫耳氫氣產生的量為116.62 (TOF= 116.62 h-1)。在我們的研究中，釕基氫團簇的催化產氫效率優於其他鐵基氫團簇的研究，而這些仿生性氫團簇詳細的催化機制於文中有更進一步的討論。我們希望透過此仿生性釕基氫團簇的合成與建構，能使其應用於未來光催化氫能源工業上。

Hydrogen, which is renewable and non-polluting, has been considered as an alternative energy to fossil fuel. In nature, hydrogenases (H2ase) can catalyze the reversible oxidation-reduction reaction (2H+ + 2e- ↔ H2) to produce hydrogen. The active site of [FeFe]ase, a dithiolate-bridged diiron complex, called the H-cluster, has been used as a biomimetic photochemical catalyst for light-driven hydrogen production. The goal of the present study is to mimic the structure of H-cluster by substituting the center metal iron with ruthenium. In this research, ruthenium-based H-clusters, [Ru2(CO)6(-S(CH2)3S)] and [(Ru3(CO)10)2(-S(CH2)3S)] are synthesized and characterized by NMR, MS, FT-IR spectroscopy and single crystal X-ray structure determination. The photocatalytic activity of these ruthenium-based H-clusters clusters in hydrogen production is investigated using different proton sources, such as water and formic acid. In addition, we evaluate the effects of a series of electron-donating phosphine ligands additions on the photocatalytic system for hydrogen production. The results show that hydrogen production obtained from formic acid is better than from water. In the organic phase, with formic acid as a proton source, ruthenium-based H-clusters show high efficiency for hydrogen evolution in the presence of P-ligands, and the hydrogen yield obtained from the P-ligands with electron donating functional group is higher than the P-ligands with electron withdrawing functional group. The best turnover frequency (TOF) 116.62 h-1 is observed with [Ru3(CO)10]2[-S(CH2)3S] as the photocatalyst in presence of tris(4-methoxyphenyl)phosphine (P(p-C6H4OMe)3) under Xe lamp (500 W) irradiation. The efficiency of hydrogen production is better than in previous studies. The detailed catalytic mechanism of these artificial biomimetic H-clusters is further discussed. In the future, ruthenium-based H-clusters will be promising catalysts in the light-driven hydrogen production industry.