本文要点：
动态共价有机骨架(COFs)在客体分子的物理吸附作用下，可以在具有不同晶胞参数和孔隙率的晶相之间可逆地转换。虽然三维框架的晶胞体积发生了令人印象深刻的变化，但2D COFs的溶剂诱导体积变化仍然相对较小。
作者现在已经开发了一系列2D COFs，其中系统地改变了互连桥单元的长度。相对于无溶剂收缩的COFs的体积，优化的材料实现了高达85%的溶剂诱导的膨胀。
这些结构变化是完全可逆的，并且框架完全保持其高度的晶体有序性。
这项研究介绍了动态2D COFs的通用设计策略，这可能使这些材料在气体分离和传感的未来应用。
Figure 1. (a) Wine-rack type dynamic frameworks expand predominantly in one dimension upon uptake of guest molecules. (b) Chemical structures of the PDI COFs with different bridge units.
Figure 2. Solvent-induced dynamic phase transitions of the PDI-3P COF. (a) PXRD analysis and Pawley refinement of the solvent-free (cp phase) COF. The porosity of this phase is very low (Connolly surface shown in light blue). (b) PDI-3P COF ip phase, observed at low toluene loading. (c) PDI-3P COF op phase, observed at high toluene loading. The op phase COF has accessible pores with a triangular cross-section. The hexyl chains adopt a head-to-head configuration with only small overlap. (d, e) In situ PXRD recorded during toluene vapor adsorption/desorption.(f) Toluene uptake causes a 76% expansion of the unit cell along a·sin(β), i.e., perpendicular to the pores, and an increase in unit cell volume of 74%.
Figure 3. (a) Lattice expansion of the PDI-3P COF upon loading with different solvents. The bulky cyclohexane promotes the strongest expansion and causes an 85% increase in unit cell volume. (b) Comparison of the PDI-3P COF op phase structure models after loading with different solvents.
https://doi.org/10.1021/jacs.4c08918
