Selective
detection of active ingredients in complex samples has
always been a crucial challenge because there are many disturbing
compounds, especially structural analogues that interfere with the
detection. In this work, a fluorescent covalent organic framework
(named COF-TD), which can be used for the selective fluorescence detection
and enrichment of myricetin from complex samples, was reported for
the first time. The highly crystalline COF-TD with bright blue fluorescence
was formed through a solution polymerization method by the condensation
reaction between 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)trianiline
and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde. Due to spatial size
selectivity, multisites hydrogen bonding, and π–π
interaction, myricetin can quench the fluorescence of COF-TD with
an inner filter effect (IFE) and static quenching mechanisms as well
as can be enriched on COF-TD. Myricetin can observably eliminate the
interference of other compounds and selectively quench the fluorescence
of COF-TD with a limit of detection (LOD) of 0.30 μg·mL–1. The high adsorption ability of COF-TD (Q = 124.6 mg·g–1) to myricetin was also obtained.
Finally, a sensing platform based on COF-TD for myricetin was successfully
developed and applied for the detection of myricetin from vine teas.
In addition, COF-TD also showed good water sensing ability and could
be used effectively to detect water content in organic solvent (1–18%
water in acetone, 0.5–5% water in acetonitrile, 1–4.5%
water in ethyl acetate, v/v). To the best of our knowledge, this is
the first report where COF-TD was used to detect water in a relatively
wide concentration range. In all, this work provided dual-functional
fluorescent COFs with the properties of an adsorbent, opening up new
methodologies for the simple, selective, and enrichment detection
method for myricetin.
