Hydroxyl-riched covalent organic framework for solid-phase microextraction of flavonoids aglycones or their metabolites in mice's plasma: Luteolin and quercetagetin as examples

•Hydroxyl-riched COF-DES-1 was employed as the coating of SPME fiber.•COF-DES-1 based SPME fiber showed outstanding protein exclusion effects.•The developed SPME fiber had good adsorption effects for luteolin and quercetagetin.•The fiber was used to extract target flavonoids aglycones or metabolites from plasma sample.