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.

多孔共价有机骨架（COF）能够实现具有分子精度的功能材料。过去的研究通常集中于生成刚性框架，其中结构和光电特性是静态的。在这里，我们报道了动态二维（2D）COF，它们可以在吸收或去除客体时打开和关闭其孔，同时保留其结晶长程有序。构建动态、清晰且强大的框架需要良好控制的灵活性。我们通过“酒架”设计实现了这一目标，其中刚性π堆叠的苝二酰亚胺柱通过非堆叠的柔性桥互连。所得 COF 在各自的收缩孔和开孔构象之间显示出逐步相变，晶胞体积增加高达 40%。这种可变的几何形状为引入刺激响应光电特性提供了手柄。我们通过演示可切换的光学吸收和发射特性来说明这一点，这些特性在收缩的 COF 中近似于具有单体行为的“零聚集体”。这项工作为动态 2D COF 提供了一种设计策略，可能有助于实现刺激响应材料。