Room temperature synthesis of flower-like hollow covalent organic framework for efficient enrichment of microcystins.

The morphology of nanomaterials is one of essential factors for their unique properties. Herein, a hollow covalent organic framework with a flower-like structure (HFH-COF) was synthesized at room temperature. The synthesized HFH-COF has a very large specific surface area, mesoporous structure, excellent chemical stability, and good crystallinity. The special morphology endowed HFH-COF with high specific surface area utilization and rapid mass transfer rate, resulting in faster equilibration time and better extraction performance than spherical COF (S-COF). Subsequently, combined with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), an efficient and sensitive method was established for microcystins (MCs) detection. The developed method has low detection limits (0.6-0.8 pg mL -1 ), wide linear ranges (1.5-1000.0 pg mL -1 , R ≥ 0.9993), and acceptable reproducibility (RSD ≤ 7.6%, n = 6). Real biological samples were analyzed by the developed method, and trace levels of MC-YR, MC-RR and MC-LR were detected. The results indicate that the synthesized HFH-COF is an ideal sorbent for efficient extraction of MCs from complex biological samples.