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New Mechanistic Insights into the Formation of Imine-Linked Two-Dimensional Covalent Organic Frameworks
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-10-15 , DOI: 10.1021/jacs.0c08390 Cameron Feriante 1 , Austin M. Evans 2 , Samik Jhulki 1 , Ioannina Castano 2 , Michael J. Strauss 2 , Stephen Barlow 1 , William R. Dichtel 2 , Seth R. Marder 1
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-10-15 , DOI: 10.1021/jacs.0c08390 Cameron Feriante 1 , Austin M. Evans 2 , Samik Jhulki 1 , Ioannina Castano 2 , Michael J. Strauss 2 , Stephen Barlow 1 , William R. Dichtel 2 , Seth R. Marder 1
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A more robust mechanistic understanding of imine-linked two-dimensional covalent organic frameworks (2D COFs) is needed to improve their crystalline domain sizes and to control their morphology, both of which are necessary to fully realize their application potential. Here, we present evidence that 2D imine-linked COFs rapidly polymerize as crystalline sheets that subsequently reorganize to form stacked structures. Primarily, this study focuses on the first few minutes of 1,3,5-tris(4-aminophenyl)benzene and terephthaldehyde polymerization, which yields an imine-linked 2D COF. In situ X-ray diffraction and thorough characterization of solids obtained using gentler isolation and activation methods than have typically been used in the literature indicate that periodic imine-linked 2D structures form within 60 s, which then form more ordered stacked structures over the course of several hours. This stacking process imparts improved stability toward the isolation process relative to that of the early stage materials, which likely obfuscated previous mechanistic conclusions regarding 2D polymerization that were based on products isolated using harsh activation methods. This revised mechanistic picture has useful implications; the 2D COF layers isolated at very short reaction times are easily exfoliated, as observed in this work using high-resolution transmission electron microscopy and atomic force microscopy. These results suggest improved control of imine-linked 2D COF formation can be obtained through manipulation of the polymerization conditions and interlayer interactions. Qualitatively similar results were obtained for analogous materials obtained from 2,5-di(alkoxy)terephthaldehyde derivatives, except for the COF with the longest alkoxy chains examined (OC12H25), which, although shown by in situ X-ray diffraction to be highly crystalline in the reaction mixture, is much less crystalline when isolated than the other COFs examined, likely due to the more severe steric impact of the dodecyloxy functionality on the stacking process.
中文翻译：
对亚胺连接的二维共价有机框架形成的新机制见解
需要对亚胺连接的二维共价有机骨架 (2D COF) 进行更可靠的机械理解，以改善其晶畴尺寸并控制其形态，这两者都是充分发挥其应用潜力所必需的。在这里，我们提出证据表明，二维亚胺连接的 COF 迅速聚合为结晶片，随后重组形成堆叠结构。本研究主要关注 1,3,5-三（4-氨基苯基）苯和对苯二醛聚合的前几分钟，这会产生亚胺连接的 2D COF。使用比文献中通常使用的更温和的分离和活化方法获得的固体的原位 X 射线衍射和彻底表征表明，在 60 秒内形成了周期性亚胺连接的二维结构，然后在几个小时内形成更有序的堆叠结构。相对于早期材料，这种堆叠过程赋予隔离过程更高的稳定性，这可能混淆了先前基于使用苛刻活化方法隔离的产品的二维聚合的机械结论。这个修改后的机械图具有有用的意义；在非常短的反应时间内隔离的 2D COF 层很容易剥落，正如在这项工作中使用高分辨率透射电子显微镜和原子力显微镜观察到的那样。这些结果表明，可以通过控制聚合条件和层间相互作用来改善对亚胺连接的 2D COF 形成的控制。
更新日期：2020-10-15
中文翻译：
对亚胺连接的二维共价有机框架形成的新机制见解
需要对亚胺连接的二维共价有机骨架 (2D COF) 进行更可靠的机械理解，以改善其晶畴尺寸并控制其形态，这两者都是充分发挥其应用潜力所必需的。在这里，我们提出证据表明，二维亚胺连接的 COF 迅速聚合为结晶片，随后重组形成堆叠结构。本研究主要关注 1,3,5-三（4-氨基苯基）苯和对苯二醛聚合的前几分钟，这会产生亚胺连接的 2D COF。使用比文献中通常使用的更温和的分离和活化方法获得的固体的原位 X 射线衍射和彻底表征表明，在 60 秒内形成了周期性亚胺连接的二维结构，然后在几个小时内形成更有序的堆叠结构。相对于早期材料，这种堆叠过程赋予隔离过程更高的稳定性，这可能混淆了先前基于使用苛刻活化方法隔离的产品的二维聚合的机械结论。这个修改后的机械图具有有用的意义；在非常短的反应时间内隔离的 2D COF 层很容易剥落，正如在这项工作中使用高分辨率透射电子显微镜和原子力显微镜观察到的那样。这些结果表明，可以通过控制聚合条件和层间相互作用来改善对亚胺连接的 2D COF 形成的控制。
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