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Ester-linked, crystalline, porous covalent organic frameworks (COFs) have been synthesized and structurally characterized. Transesterification reactions between ditopic 2-pyridinyl aromatic carboxylates and tri- or tetratopic phenols gave the corresponding ester-linked COFs. They crystallize as 2D structures in kgm (COF-119) and hcb (COF-120, 121, 122) topologies with surface areas of up to 2092 m2/g. Notably, crystalline COF-122 comprises edges spanning over 10 phenylene units, an aspect that had only been achieved in metal-organic frameworks. This work expands the scope of reticular chemistry to include, for the first time, crystalline ester-linked COFs related to common polyesters.

2D covalent organic frameworks (COFs) with flexible urea linkages have been synthesized by condensation of 1,3,5-triformylphloroglucinol (TFP) with 1,4-phenylenediurea (BDU) or 1,1'-(3,3'-dimethyl-[1,1'-biphenyl]-4,4'-diyl)diurea (DMBDU). The resulting COF-117 and COF-118 undergo reversible structural dynamics within their layers, in response to inclusion and removal of guest molecules, emanating from urea C-N bond rotation and interlayer hydrogen-bonding interactions. These compounds are the first urea-linked COFs, serving to expand the scope of reticular chemistry.