Dual mode in a metal-organic framework based mixed matrix membrane for discriminative detection of amines: Vapoluminescent and vapochromic response

The determination of amines is of great interest not only for monitoring food quality and disease state but also protecting human health from exposure to toxic amines. Herein, the utilization of the active functional site (-OH) of dht ligand based on luminescent [Cd2(dht)(idc)(H2O)4] (1) ; H2dht = 2,5-dihydroxyterephthalic acid and H2idc = 4,5-imidazoledicarboxylic acid can serve excited-state proton transfer (ESPT) together with enolketo tautomerism for sensing amines. The sensor exhibits dual mode for detecting amines in terms of vapoluminescent process based on shifted emission and vapochromic process based on colorimetric detection. This probe not only displays dual mechanism toward methylamine through "turn-off" in low concentration and redshifted emission in high concentration but also can sense pyridine through blue-shifted emission. Besides, it also shows discriminative color detection within the same group of amines. This material exhibits high selectivity, short response, wide range of detection in coverage of safety and danger levels for human health, good repeatability and reproducibility as well as low detection limit which is lower than the harmful level in human being. In addition, the metal-organic framework based mixed matrix membrane has been prepared and applied for quantitative analysis of amines in real time through smartphone.