Kagóme Cobalt(II)-Organic Layers as Robust Scaffolds for Highly Efficient Photocatalytic Oxygen Evolution
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- 作者：Jiaheng Xu ; Zhi Wang ; Wenguang Yu ; Dr. Di Sun ; Dr. Qing Zhang ; Dr. Chen-Ho Tung and Dr. Wenguang Wang
- 刊名：ChemSusChem
- 出版年：2016
- 出版时间：May 23, 2016
- 年：2016
- 卷：9
- 期：10
- 页码：1146-1152
- 全文大小：1136K
- ISSN：1864-564X
文摘
Two Kagóme cobalt(II)-organic layers of [Co3(μ3-OH)2(bdc)2]n (1) and [Co3(μ3-OH)2(chdc)2]n (2) (bdc=o-benzenedicarboxylate and chdc=1,2-cyclohexanedicarboxylate) that bear bridging OH− ligands were explored as water oxidation catalysts (WOCs) for photocatalytic O2 production. The activities of 1 and 2 towards H2O oxidation were assessed by monitoring the in situ O2 concentration versus time in the reaction medium by utilizing a Clark-type oxygen electrode under photochemical conditions. The oxygen evolution rate (R ) was 24.3 μmol s−1 g−1 for 1 and 48.8 μmol s−1 g−1 for 2 at pH 8.0. Photocatalytic reaction studies show that 1 and 2 exhibit enhanced activities toward the oxidation of water compared to commercial nanosized Co3O4. In scaled-up photoreactions, the pH value of the reaction medium decreased from 8.0 to around 7.0 after 20 min and the O2 production ceased. Based on the amounts of the sacrificial oxidant (K2S2O8) used, the yield of O2 produced is 49.6 % for 2 and 29.8 % for 1. However, the catalyst can be recycled without a significant loss of catalytic activity. Spectroscopic studies suggest that the structure and composition of recycled 1 and 2 are maintained. In isotope-labeling H218O (97 % enriched) experiments, the distribution of 16O16O/16O18O/18O18O detected was 0:7.55:92.45, which is comparable to the theoretical values of 0.09:5.82:94.09. This work not only provides new catalysts that resemble ligand-protected cobalt oxide materials but also establishes the significance of the existence of OH− (or H2O) binding sites at the metal center in WOCs.