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.

Ester-linked, crystalline, porous, covalent organic frameworks (COFs) have been synthesized and structurally characterized. Transesterification reactions between di-topic 2-pyridinyl aromatic carboxylates and tri-or tetra-topic 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 2,092 m 2 /g. Notably, crystalline COF-122 comprises edges spanning over 10 phenylene units; an aspect 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.