Department of Chemistry and Molecular Biology, University of Gothenburg, Kemigården 4, 412 96 Göteborg, Sweden.
Division of Energy and Environmental Measurement, National Institute of Metrology, China NIM, Beijing 100013, P.R. China.
J Am Chem Soc. 2020 Apr 8;142(14):6548-6553. doi: 10.1021/jacs.9b10884. Epub 2020 Mar 26.
Inherently porous materials that are chemically and structurally robust are challenging to construct. Conventionally, dynamic chemistry is thought to be needed for the formation of uniform porous organic frameworks, but dynamic bonds can limit the stability of these materials. For this reason, all-carbon-linked frameworks are expected to exhibit higher stability performance than more traditional porous frameworks. However, the limited reversibility of carbon-carbon bond-forming reactions has restricted the exploration of these materials. In particular, the challenges associated with producing uniform thin films of all-carbon-linked frameworks has inhibited the study of these materials in applications where well-defined films are required. Here, we synthesize continuous and homogeneous films of two different all-carbon-linked three-dimensional porous aromatic frameworks with nanometer-precision thickness (PAF-1 and BCMP-2). This was accomplished by kinetically promoting surface reactivity while suppressing homogeneous nucleation. Through connection of the PAF film to a gold substrate via a self-assembled monolayer and use of flow conditions to continually introduce monomers, smooth and continuous PAF films can be grown with controlled thickness. This strategy allows traditional transition metal mediated carbon-carbon cross-coupling reactions to form porous, organic thin films. We expect that the chemical principles uncovered in this study will enable the synthesis of a variety of chemically and structurally diverse carbon-carbon-linked frameworks as high-quality films, which are inaccessible by conventional methods.
具有化学和结构稳定性的本征多孔材料的构建具有挑战性。通常认为动态化学对于形成均匀的多孔有机骨架是必要的，但动态键会限制这些材料的稳定性。出于这个原因，全碳连接的骨架有望比更传统的多孔骨架表现出更高的稳定性。然而，碳-碳键形成反应的有限可逆性限制了对这些材料的探索。特别是，与制备全碳连接的骨架的均匀薄膜相关的挑战抑制了这些材料在需要明确定义薄膜的应用中的研究。在这里，我们通过动力学促进表面反应同时抑制均相成核，合成了两种不同的全碳连接的三维多孔芳香骨架（PAF-1 和 BCMP-2）的连续和均匀薄膜，具有纳米级精度的厚度。通过将 PAF 薄膜通过自组装单分子层连接到金基底，并使用流动条件不断引入单体，可以生长具有可控厚度的光滑连续的 PAF 薄膜。这种策略允许传统的过渡金属介导的碳-碳交叉偶联反应形成多孔有机薄膜。我们预计，本研究中揭示的化学原理将能够合成各种化学和结构多样化的全碳连接的骨架作为高质量的薄膜，这是传统方法无法实现的。
