德国慕尼黑大学Thomas Bein研究团队的一项最新研究提出了动态二维共价有机框架（COFs）。这一研究成果于2024年5月3日发表在国际顶尖学术期刊《自然—化学》上。

在该研究中，该研究组报道了动态二维(2D) COFs，它可以在吸收或去除客体时打开和关闭它们的孔隙，同时保持它们的晶体长程秩序。构建动态的、结晶的和稳定的框架需要良好控制的灵活性程度。研究人员通过“酒架”设计实现了这一点，其中刚性π堆叠的苝二酰亚胺柱通过非堆叠的柔性桥梁相互连接。所得到的COFs在其各自的收缩孔和开孔构象之间显示出逐步相变，单位细胞体积增加高达40%。

这种可变的几何形状为引入刺激响应光电特性提供了一个手柄。研究组通过展示可切换的光学吸收和发射特性来说明这一点，这在收缩的COFs中近似于具有单体行为的“零聚集体”。这项工作提供了一种动态二维COFs的设计策略，这可能用于实现刺激响应材料。

据研究人员介绍，多孔共价有机框架(COFs)使具有分子精度的功能材料得以实现。过去的研究通常集中在产生刚性框架，其中结构和光电子特性是静态的。

附：英文原文

Title: Dynamic two-dimensional covalent organic frameworks

Author: Auras, Florian, Ascherl, Laura, Bon, Volodymyr, Vornholt, Simon M., Krause, Simon, Dblinger, Markus, Bessinger, Derya, Reuter, Stephan, Chapman, Karena W., Kaskel, Stefan, Friend, Richard H., Bein, Thomas

Issue&Volume: 2024-05-03

Abstract: Porous covalent organic frameworks (COFs) enable the realization of functional materials with molecular precision. Past research has typically focused on generating rigid frameworks where structural and optoelectronic properties are static. Here we report dynamic two-dimensional (2D) COFs that can open and close their pores upon uptake or removal of guests while retaining their crystalline long-range order. Constructing dynamic, yet crystalline and robust frameworks requires a well-controlled degree of flexibility. We have achieved this through a ‘wine rack’ design where rigid π-stacked columns of perylene diimides are interconnected by non-stacked, flexible bridges. The resulting COFs show stepwise phase transformations between their respective contracted-pore and open-pore conformations with up to 40% increase in unit-cell volume. This variable geometry provides a handle for introducing stimuli-responsive optoelectronic properties. We illustrate this by demonstrating switchable optical absorption and emission characteristics, which approximate ‘null-aggregates’ with monomer-like behaviour in the contracted COFs. This work provides a design strategy for dynamic 2D COFs that are potentially useful for realizing stimuli-responsive materials.

DOI: 10.1038/s41557-024-01527-8

Source: https://www.nature.com/articles/s41557-024-01527-8