Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan.
Proc Natl Acad Sci U S A. 2012 Sep 25;109(39):15673-8. doi: 10.1073/pnas.1118336109. Epub 2012 Aug 20.
Previously undescribed supramolecules constructed with various ratios of two kinds of Ru(II) complexes-a photosensitizer and a catalyst-were synthesized. These complexes can photocatalyze the reduction of CO(2) to formic acid with high selectivity and durability using a wide range of wavelengths of visible light and NADH model compounds as electron donors in a mixed solution of dimethylformamide-triethanolamine. Using a higher ratio of the photosensitizer unit to the catalyst unit led to a higher yield of formic acid. In particular, of the reported photocatalysts, a trinuclear complex with two photosensitizer units and one catalyst unit photocatalyzed CO(2) reduction (Φ(HCOOH) = 0.061, TON(HCOOH) = 671) with the fastest reaction rate (TOF(HCOOH) = 11.6 min(-1)). On the other hand, photocatalyses of a mixed system containing two kinds of model mononuclear Ru(II) complexes, and supramolecules with a higher ratio of the catalyst unit were much less efficient, and black oligomers and polymers were produced from the Ru complexes during photocatalytic reactions, which reduced the yield of formic acid. The photocatalytic formation of formic acid using the supramolecules described herein proceeds via two sequential processes: the photochemical reduction of the photosensitizer unit by NADH model compounds and intramolecular electron transfer to the catalyst unit.
先前未曾描述过的超分子结构是由两种 Ru(II) 配合物（一种光敏剂和一种催化剂）以不同比例构建而成。这些配合物可以在二甲酰胺-三乙醇胺混合溶液中使用广泛波长的可见光和 NADH 模型化合物作为电子供体，高选择性和高耐久性地光催化还原 CO2 形成甲酸。使用更高比例的光敏剂单元与催化剂单元会导致甲酸的产率更高。特别是，在所报道的光催化剂中，具有两个光敏剂单元和一个催化剂单元的三聚核配合物光催化 CO2 还原（Φ（HCOOH）= 0.061，TON（HCOOH）= 671）具有最快的反应速率（TOF（HCOOH）= 11.6 min-1）。另一方面，包含两种模型单核 Ru(II) 配合物的混合体系和催化剂单元比例更高的超分子的光催化效率要低得多，并且在光催化反应过程中 Ru 配合物会生成黑色寡聚物和聚合物，从而降低了甲酸的产率。本文所述的超分子的甲酸光催化形成过程通过两个连续的过程进行：NADH 模型化合物对光敏剂单元的光化学还原和分子内电子转移到催化剂单元。
