An UV equipped box for photoactivation with a fluorescent coordination polymer for recognizing amine gases by “turn-color” in air

A low-cost and convenient fluorescent indicator of alkaline earth metal-organic coordination polymer Sr(H2ABTC)(DMF)(H2O) (1) (ABTC = 3,3,5,5-azobenzenetetracarboxylic acid) was designed and synthesized by using a flexible ligand ABTC and alkaline earth metal ion Sr2+ for sensing trace amine gases in the air. The complex 1 was characterized by X-ray single crystal measurement, mainly composed of conjugated fluorophore and uncoordinated carboxyl groups. A series of detailed experiments confirmed the dramatic change of fluorescence color under ultraviolet. When the complex 1 interacted with amine gases, its fluorescence emission intensity is enhanced and emission peak redshift greatly. Of most important, convenient fluorescence detection for amine gases was realized by a homemade indicator box, which was reusable and allowed to detect the concentration of amine gases down to 10 ppb (parts per billion) upon real-time (3 min). The sensing mechanisms were analyzed through the closed-loop stiffening effect and the enhanced conjugate effect.