Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.
School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022, China.
J Am Chem Soc. 2022 Jan 19;144(2):695-700. doi: 10.1021/jacs.1c11707. Epub 2022 Jan 6.
In nature, water is oxidized by plastoquinone to evolve O and form plastoquinol in Photosystem II (PSII), whereas NADP is reduced by plastoquinol to produce NADPH and regenerate plastoquinone in Photosystem I (PSI), using homogeneous molecular photocatalysts. However, water splitting to evolve H and O in a 2:1 stoichiometric ratio has yet to be achieved using homogeneous molecular photocatalysts, remaining as one of the biggest challenges in science. Herein, we demonstrate overall water splitting to evolve H and O in a 2:1 ratio using a two liquid membranes system composed of two toluene phases, which are separated by a solvent mixture of water and trifluoroethanol (HO/TFE, 3:1 v/v), with a glass membrane to combine PSI and PSII molecular models. A PSII model contains plastoquinone analogs [-benzoquinone derivatives (X-Q)] in toluene and an iron(II) complex as a molecular oxidation catalyst in HO/TFE (3:1 v/v), which evolves a stoichiometric amount of O and forms plastoquinol analogs (X-QH) under photoirradiation. On the other hand, a PSI model contains nothing in toluene but contains X-QH, 9-mesityl-10-methylacridinium ion (Acr-Mes) as a photocatalyst, and a cobalt(III) complex as an H evolution catalyst in HO/TFE (3:1 v/v), which evolves a stoichiometric amount of H and forms X-Q under photoirradiation. When a PSII model system is combined with a PSI model system with two glass membranes and two liquid membranes, photocatalytic water splitting with homogeneous molecular photocatalysts is achieved to evolve hydrogen and oxygen with the turnover number (TON) of >100.
在自然界中，水被质体醌氧化以产生 O 并在光系统 II（PSII）中形成质体醌醇，而 NADP 则被质体醌醇还原以在光系统 I（PSI）中产生 NADPH 并再生质体醌，使用均相分子光催化剂。然而，使用均相分子光催化剂将水分解以按 2:1 的化学计量比产生 H 和 O 尚未实现，这仍然是科学面临的最大挑战之一。在此，我们使用由两个甲苯相组成的两相膜系统来演示以 2:1 的比例整体分解水以产生 H 和 O，该系统由水和三氟乙醇（HO/TFE，3:1 v/v）的溶剂混合物隔开，并用玻璃膜将 PSI 和 PSII 分子模型结合在一起。PSII 模型在甲苯中包含质体醌类似物[-苯醌衍生物（X-Q）]，在 HO/TFE（3:1 v/v）中包含铁(II) 配合物作为分子氧化催化剂，在光照射下会产生化学计量的 O 并形成质体醌醇类似物（X-QH）。另一方面，PSI 模型在甲苯中不包含任何物质，但在 HO/TFE（3:1 v/v）中包含 X-QH、9-均三甲苯基-10-甲基吖啶鎓离子（Acr-Mes）作为光催化剂和钴(III) 配合物作为 H 演化催化剂，在光照射下会产生化学计量的 H 并形成 X-Q。当将 PSII 模型系统与具有两个玻璃膜和两个液体膜的 PSI 模型系统结合时，使用均相分子光催化剂实现了光催化水分解，以产生具有 >100 周转数（TON）的氢和氧。
