| Summary: | 碩士 === 國立交通大學 === 生物科技學系 === 104 === Hydrogen has been regarded as a promising alternative energy candidate. Hydrogenases are enzymes that catalyze the reversible reduction of protons to hydrogen (H+ + 2 e-↔ H2). Due to the high catalytic activity of [FeFe] hydrogenases, their active sites (the H-clusters), have been reconstructed and used as photochemical catalysts for solar-driven hydrogen research.
In a previous study, the combination of a biomimetic ruthenium-based H-cluster [Ru2-S2-P(o-tol)3] with one equivalent of P(o-tol)3 promoted the excellent efficiency for formic acid (FA) decomposition in photocatalytic systems. Our goal was to determine if there was an improvement efficiency when the Ru2-S2 was substituted with two phosphine ligands (P-ligands). We then attempted to investigate the PL2 effects on catalytic activity by using the Ru2-S2 complex in a photocatalytic system.
Artificial ruthenium H-clusters coordinated with aryl P-ligands were synthesized. Ru2-S2-(PLY)2, Y=1‒5 and Ru2-S2-PL2-PL3 were purified and characterized by single crystal X-ray structure determination. These Ru2-S2-di-P-ligands complexes were used as a catalyst for decomposition of formic acid in the photocatalytic system. On the other hand, the combinations of Ru2-S2 and several kinds of alkyl phosphine were used for in situ catalysis. The Ru2-S2-(PL7)4 structure was also determined by X-ray.
The observation suggests that Ru2-S2 linked with di-P-Ligands has no significant improvement on H2 generation efficiency. The PL6 and PL7 showed excellent efficiency (TOF 15753 h-1 and 18420 h-1) after 45 min. A further mechanism of study for PL2 effects on Ru2-S2 complexes were monitored in a photocatalytic system. FTIR (Fourier transform infrared spectroscopy) results indicate that the bulky PL2 is easily eliminated from the Ru2-S2-PL2 and back coordinates with other Ru2-S2 species. In EI-MS, the results present the possibility of Ru2-S2-formate complex. Although the results structure are not in line with expectations, two new photo-induced complexes (Ru2-S2-P(o-tol)2 and Ru2-S2-[P(o-tol)2THF]) were found and characterized by X-ray.
When more information about the association between the artificial ruthenium H-cluster and P-ligands is obtained, the catalytic mechanism will become gradually clearer. These results could help us develop new Ru-carbonyl precursors or P-ligands for improving the efficiency of hydrogen production.
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