仿生性雙硫架橋鋨-硫複合物之合成與其光催化產氫之應用

Abstract

氫氣是一種乾淨、可循環再利用，並被公認為可取代石化燃料的再生性能源。在自然界中，產氫酶(Hydrogenases)和氫氣的生成有密切關係。最近的研究發現利用仿生性合成鐵-鐵產氫酶([Fe-Fe] hydrogenase)的活性中心-氫簇分子(H-cluster)可被應用於光催化氫氣的產生。所以我們合成了一系列雙硫醇架橋之鋨-硫複合物[Os3(S2C3H6)(μ-X)(CO)n] (X = H, COOH; n = 7, 9 etc.)去模擬氫簇分子(H-cluster)的結構，並藉由核磁共振光譜儀(NMR)、電噴灑質譜儀(ESI-MS)以及傅立葉轉換紅外線光譜儀(FT-IR)進行產物的分析及其結構鑑定。此外，利用紫外光-可見光光譜儀(UV-Vis spectrum)及伏安循環法(cyclic voltammetry) 我們可以測量有機金屬鋨-硫複合物的吸收光波長與其電化學性質。進一步，我們分別利用有機相和水相兩種不同的光催化反應系統探討這些有機金屬鋨-硫複合物的產氫活性。另外，我們外加三種具有不同推拉電子特性的含磷化合物-(三苯基膦 (triphenylphosphine (P(Phe)3))、三吡咯膦(tripyrrolephosphine (P(Pyr)3))及三吡咯啶膦(tripyrrolidinephosphine (P(Pyrldn)3))，和改變不同溫度(25 ˚C 或40 ˚C)探討條件改變下對於照光催化之產氫活性的影響。結果顯示，在溫度40 ˚C下，使用500 W光源照光，並搭配有機相之反應條件，[Os6(aspH)(CO)20] (X-1) + P(Pyr)3能表現出最好的產氫效能，其每小時每莫耳化合物催化每莫耳產氫量為9.07 (TOF = 9.07)。之後我們將進一步去研究內含共價鍵結含磷化合物的雙硫架橋之鋨-硫複合物是否能增加其光催化產氫的效能，並嘗試解出已合成的雙硫架橋之鋨複合物[Os3(S2C3H6)(μ-X)(CO)n] (X = H, COOH)的其X-ray結晶結構，以期待未來能對雙硫架橋之鋨-硫複合物其光催化產氫的機制有所了解。

Hydrogen is a clean renewable energy, putatively to replace fossil energy. In nature, hydrogenses (H2ases) have been closely related with hydrogen evolution. Recent findings allow insight into the active site of the [Fe-Fe] hydrogenase, H-cluster, which catalyzes the reaction of hydrogen production. A series of osmium-sulfur clusters including Os3(CO)12 and various [Os3(S2C3H6)(μ-X)(CO)n] (X = H, COOH; n = 7, 9 etc.) complexes, have been synthesized, purified, and characterized by NMR, IR, and MS spectra. Furthermore, optical characteristics and electrochemical properties of these osmium-sulfur clusters were analyzed by UV-Vis spectrum and cyclic voltammetry. The synthesized osmium-sulfur clusters were subjected to photocatalytic hydrogen generation studies using in the organic phase and the aqueous phase, respectively. In addition, different P-ligands, including (triphenylphosphine (P(Phe)3), tripyrrolephosphine (P(Pyr)3), and tripyrrolidinephosphine (P(Pyrldn)3)) as well as various temperatures (25 ˚C and 40 ˚C) were used to investigate their effects on hydrogen production efficiency. The results showed that [Os6(aspH)(CO)20] (X-1) + P(Pyr)3 exhibits the best hydrogen production efficiency when X-1 was photoirradiated under Xe lamp (500 W) at 40 ˚C in organic phase (TOF = 9.07 h-1). Further studies will focus on the covalent modification of P-ligand onto the osmium-sulfur complexes to improve the efficiency of photocatalytic hydrogen generation and to solve the structures of those osmium-sulfur clusters by X-ray crystallography. The mechanism of hydrogen evolution by various osmium-sulfur clusters will also be elucidated in future.