We report the collective alignment of molecular chromophores in the backbone of covalent organic frameworks (COFs) as a new chemical approach to construct efficient two-photon absorption (2PA) materials. Six imine COFs were synthesized from aldehyde-terminated triarylamine linkers and p-phenylenediamine. Attainment of these COFs in single-crystal form revealed the underlying layered structures and precise spatial arrangements of the constituent chromophores including an unusual serrated packing between the layers. Coherent orientation of chromophores within each layer made possible collective alignment of their transition dipoles, while the serrated packing between the layers maximized the crystal anisotropy. As a result, the full potential of molecular chromophores for 2PA was developed. Up to 110-fold enhancement of two-photon action cross-section (2PACS) was achieved for the COFs relative to their constituents, with one member exhibiting a high 2PACS value of 8,756 GM/chromophore-standing among the best molecule-based 2PA materials.

我们报告了共价有机框架（COFs）的骨架中分子发色团的集体排列，作为一种构造有效的双光子吸收（2PA）材料的新化学方法。由醛封端的三芳基胺连接基和p合成了六个亚胺COF-苯二胺。以单晶形式获得这些COF揭示了潜在的层状结构和组成生色团的精确空间排列，包括各层之间不寻常的锯齿状堆积。每层内发色团的相干取向使得它们的跃迁偶极可以集体对齐，而各层之间的锯齿状堆积使晶体各向异性最大化。结果，开发了分子发色团对2PA的全部潜力。相对于其成分，COF的双光子作用截面（2PACS）达到110倍的增强，其中一个成员表现出最高的2PACS值为8,756 GM /生色团，是基于分子的最佳2PA材料中的佼佼者。