Reticular Design and Synthesis of Covalent Organic Frameworks with Irregular Hexagonal Tiling

Reticular chemistry has greatly stimulated the development of framework materials, yet covalent organic frameworks (COFs) featuring irregular tiling are rare, because of the strict constraints on irregular tile lengths and angles. Guided by reticular chemistry, we deconstructed type III irregular hexagonal tiling into a combination of D_2h + D_2h monomers and achieved the first successful synthesis of 2D COFs featuring such tiling with hit topology. By tuning the crystal growth conditions, we obtained a set of reticular isomers, COF-hit and COF-bex, with distinct reticular structures. Powder X-ray diffraction and high-resolution transmission electron microscopy were employed to precisely characterize their topology structures. COF-hit demonstrates outstanding water absorption capabilities under high humidity conditions. This rational design of COFs using irregular tiling opens a new avenue to diversify the structural types and topological varieties of COFs and promote the development of reticular chemistry.