Synthesis of phenylboronic acid-functionalized covalent organic framework via thiol-ene “click” reaction for highly efficient adsorption of cis-diol containing flavonoids

Owing to tailor-made functionalization, high specific surface areas and tunable pore sizes, covalent organic frameworks (COFs) have been increasingly used in the adsorption area. Herein, a novel COF TzDa-PBA containing phenylboronic acid groups was facilely prepared through a post-modification strategy. The COF TzDa-PBA was synthesized by amine-aldehyde condensation reaction of the 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)trianiline (Tz) and 2,5-diallyloxyterephthalaldehyde (Da-V) through a room-temperature synthetic process to form a vinyl-functionalized COF TzDa-V, followed by covalent linking of 4-mercaptophenylboronic acid (4-MPBA) through the thiol-ene “click” reaction. As a proof-of-concept, the as-obtained TzDa-PBA was used as an adsorbent to adsorb cis-diol containing flavonoids. Representatively, due to its distinctive structure and boronic acid group functional properties, TzDa-PBA showed exceptional adsorption performance for cis-diol containing flavonoids, affording luteolin (LTL) capacity of 219.3 mg g−1, surpassing all those of boronic acid-functionalized materials reported thus far. Furthermore, a commercially available LTL with 85% purity could be easily enriched and further purified by using TzDa-PBA. COF TzDa-PBA with good reusability is promising as adsorbent for selective capture of cis-diol containing flavonoids.