Crystal size effect is of vital importance in materials science by exerting significant influence on various properties of materials and furthermore their functions. Crystal size effect of covalent organic frameworks (COFs) has never been reported because their controllable synthesis is difficult, despite their promising properties have been exhibited in many aspects. Here, we report the diverse crystal size effects of two representative COFs based on the successful realization of crystal-size-controlled synthesis. For LZU-111 with rigid spiral channels, size effect reflects in pore surface area by influencing the pore integrity, while for flexible COF-300 with straight channels, crystal size controls structural flexibility by altering the number of repeating units, which eventually changes sorption selectivity. With the understanding and insight of the structure-property correlation not only at microscale but also at mesoscale for COFs, this research will push the COF field step forward to a significant advancement in practical applications.

晶体尺寸效应在材料科学中至关重要，因为它会对材料的各种特性及其功能产生重大影响。尽管共价有机骨架（COFs）的可控合成困难，尽管在许多方面都显示出令人鼓舞的性质，但由于其可控合成困难，因此从未报道过其晶体尺寸效应。在这里，我们基于成功实现晶体尺寸控制的合成，报告了两个代表性COF的不同晶体尺寸效应。对于具有刚性螺旋通道的LZU-111，尺寸影响通过影响孔的完整性反映在孔表面积中；而对于具有直通道的柔性COF-300，晶体尺寸通过改变重复单元的数量来控制结构的灵活性，最终改变吸附选择性。