Co²⁺ coordination-assisted molecularly imprinted covalent organic framework for selective extraction of ochratoxin A

Covalent organic frameworks (COFs) are attractive materials for sample pretreatment due to their tunable structures and functions. However, the precise recognition of contaminant in complex environmental matrices by COFs remains challenging owing to their insufficient specific active sites. Herein, we report Co²⁺ coordination-assisted molecularly imprinted flexible COF (MI-COF@Co²⁺) for selective recognition of ochratoxin A (OTA). The MI-COF@Co²⁺ was prepared via one-step polymerization of 3,3-dihydroxybenzidine, 2,4,6-tris(4-formylphenoxy)- 1,3,5-triazine, Co²⁺ and template. The flexible units endowed COFs with the self-adaptable ability to regulate the molecular conformation and coordinate with Co²⁺ to locate the imprinted cavities. The coordination interaction greatly improved the adsorption capacity and selectivity of MI-COF@Co²⁺ for OTA. The prepared MI-COF@Co²⁺ was used as solid phase extraction adsorbent for high-performance liquid chromatography determination of OTA with the detection limit of 0.03 ng mL^-1 and the relative standard deviation of < 2.5 %. In addition, this method permitted interference-free determination of OTA in real samples with recovery from 89.5 % to 102.8 %. This work provides a simple way to improve the selectivity of COFs for the determination of hazardous compounds in complex environments.