One-pot room temperature synthesis of Eu3+-functionalized COF and its application in ratiometric fluorescence detection of dipicolinic acid

Eu-COF was synthesized via a one-pot room-temperature method for the first time. • Dipicolinic acid triggered the emission of Eu 3+ and quench the fluorescence of COF, achieving its ratiometric detection. • The method is extendable to the fabrication of various Ln-COFs. A novel Eu 3+ -functionalized covalent organic framework (Eu-COF) was synthesized via a one-pot room-temperature Schiff base condensation between 2,5-diethoxybenzene-1,4-dicarbohydrazide (DEDH) and tetrakis(4-formylphenyl)ethylene (TFPE), breaking away from the traditional “synthesize first, modify later” strategy. The COF not only provided abundant anchoring sites for Eu 3+ ions, but also served as fluorescence reference. Dipicolinic acid (DPA) transferred energy to Eu 3+ via the antenna effect, triggering the characteristic emission of Eu 3+ at 619 nm, while the characteristic emission peak of COF at 556 nm was simultaneously reduced due to the photoinduced electron transfer and inner filter effect between COF and DPA, which led to the fluorescence quenching of COF, achieving the ratiometric detection of DPA. The synthesized Eu-COF exhibits a good linearity in the range of 0–100 μM, with a detection limit of 0.52 μM. This study pioneers the first one-pot room-temperature synthesis method for Eu 3+ -functionalized COFs. Download: Download high-res image (356KB) Download: Download full-size image