A Luminescent Lanthanide MOF for the Selective and Ultra‐High Sensitivity Detection of Caffeic Acid

ABSTRACT A novel metal–organic framework (MOF) [Eu 3 L 4 (CH 3 COO) (H 2 O) 7 ]·(CH 3 CN) 5 ( 1 ) based on the ligand H 2 L (3′,5′‐di(1H‐1,2,4‐triazole‐1‐yl)‐[1,1′‐biphenyl]‐3,5‐dicarboxylic acid) has been synthesized by the hydrothermal method. A complete characterization of 1 was conducted, employing a range of techniques including crystallography, PXRD, SEM, FTIR spectroscopy, and TGA analysis. The fluorescence sensing behavior of 1 was examined in a solution of N,N‐ dimethylformamide (DMF). The results demonstrated that 1 exhibited a pronounced “turn‐off” fluorescence phenomenon in the presence of caffeic acid (CA). Despite the interference of 11 potential substances, 1 was still capable of effectively recognizing CA. The luminescence intensity ratio of 1 showed a strong linear relationship with CA concentration in the range 0–5 μM. The K sv value was 2.49 × 10 5 M −1 . Additionally, the detection mechanism was studied using PXRD, SEM, UV–Vis, and fluorescence lifetime methods.