Iminoboronate-based chiral dynamic covalent polymer for selective and sensitive fluoride recognition

The construction of chiral polymers using dynamic covalent chemistry is a convenient and straightforward strategy for obtaining functional materials. In this paper, we report the dynamic covalent polymers DCP1, DCP2, and DCP3 with dual dynamic covalent bonds of imine and boronic ester, and their recognition of fluoride ions. The three polymers are prepared from L-DOPA hexyl ester and 2-, 3-, and 4-formylphenylboronic acids, respectively. Iminoboronate, formed within repeated DCP1 units, results in the formation of a spirochiral structure centered at sp3-B and, consequently, the chiral twist or helix conformation of the polymer backbone. DCP1 exhibits distinctive chiroptical features that distinguish it from DCP2 and DCP3. Due to the strong competitive bonding of fluoride with boron, DCP1 has a low LOD (Limit of detection) for fluoride (0.018 mg/L). DCP1 also has good selectivity for fluoride via the responsive destruction of the spirochiral structure and the chiral conformation of the backbone. The construction of these chiral dynamic polymers provides a rapid and effective approach to designing functional polymers.