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• Sulfonated functionalized magnetic COFs were prepared through a facile strategy. • The resultant composite featured mixed-mode and multiple interactions. • It exhibited excellent capture ability for β-agonists and fluoroquinolones. • Validated MSPE–LC–MS/MS method quantified β-agonists and fluoroquinolones in real samples. In this work, an efficient method for the determination of β-agonists and fluoroquinolones was established, based on a mixed-mode sorbent of magnetic sulfonated covalent organic framework composites. By coupling with HPLC–MS/MS, the main factors that affect the extraction procedure were optimized. Under the optimal conditions, the proposed HPLC–MS/MS method was successfully utilized for the extraction of β-agonists and fluoroquinolones in milk and pork meat samples. The method showed good linearities (R 2 ≥ 0.9916), and low LOQs of 0.1–0.2 ng g−1 for β-agonists and fluoroquinolones. The adsorption mechanism was investigated with the assistance of quantum chemistry calculation method, and it is worth noting that the sorbent relied mainly on the multiple adsorption mechanisms, including π–π stacking, hydrophobic, electrostatic attraction and hydrogen-bonding interactions. This work not only provides a simple method for the preparation of a mixed-mode sorbent, but also a routine analysis strategy for monitoring the illegal use of β-agonists and fluoroquinolones. [ABSTRACT FROM AUTHOR]