Xing Junfei, Schweighauser Luca, Okada Satoshi, Harano Koji, Nakamura Eiichi
Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Nat Commun. 2019 Aug 23;10(1):3608. doi: 10.1038/s41467-019-11564-4.
Chemical reactions in solution almost always take place via a series of minute intermediates that are often in rapid equilibrium with each other, and hence hardly characterizable at the level of atomistic molecular structures. We found that single-molecule atomic-resolution real-time electron microscopic (SMART-EM) video imaging provides a unique methodology for capturing and analyzing the minute reaction intermediates, as illustrated here for single prenucleation clusters (PNCs) in the reaction mixture of metal-organic frameworks (MOFs). Specifically, we found two different types of PNCs are involved in the formation of MOF-2 and MOF-5 from a mixture of zinc nitrate and benzene dicarboxylates at 95 °C and 120 °C, respectively. SMART-EM identified a small amount of 1-nm-sized cube and cube-like PNCs in the MOF-5 synthesis, but not in the MOF-2 synthesis. In the latter, we instead found only linear and square PNCs, suggesting that the MOF-2/-5 bifurcation takes place at the PNC stage.
溶液中的化学反应几乎总是通过一系列微小的中间体进行，这些中间体之间通常处于快速平衡状态，因此在原子分子结构层面上很难进行表征。我们发现，单分子原子分辨率实时电子显微镜（SMART-EM）视频成像为捕获和分析微小反应中间体提供了一种独特的方法，本文以金属有机框架（MOF）反应混合物中的单预成核簇（PNC）为例进行说明。具体而言，我们发现分别在95°C和120°C下，硝酸锌和苯二甲酸酯混合物形成MOF-2和MOF-5时涉及两种不同类型的PNC。SMART-EM在MOF-5合成中识别出少量1纳米大小的立方体和立方体状PNC，但在MOF-2合成中未识别出。在后者中，我们只发现了线性和方形PNC，这表明MOF-2/-5的分支发生在PNC阶段。
