Construction of a quinoline-4-carboxylic ester linked covalent organic framework via Doebner–von Miller reaction

The irreversible locking of reversible imine linkages in COFs into quinoline-4-carboxylic esters has been achieved for the first time through the Doebner–von Miller reaction. The high conversion efficiency and broad scope were demonstrated by synthesizing four quinoline-4-carboxylic ester-linked COFs (QCE-COFs). Subsequently, this approach was applied to create the chiral QCE-COF-Men containing l -menthol. Remarkably, QCE-COF-Men was found to release the flavorant l -menthol at elevated temperature by cleaving the weak ester bond without destroying the quinoline skeleton.