Rapid recognition of fatal cyanide in water in a wide pH range by a trifluoroacetamido based metal-organic framework

A new metal-organic-framework (MOF) called UiO-66-NH-COCF3 was prepared using a trifluoroacetamido-functionalized terephthalic acid ligand. Powder X-ray diffraction (PXRD), infrared (IR) spectroscopy, thermogravimetric analysis (TGA) and a Brunauer Emmett-Teller (BET) experiment were carried out to investigate the phase purity, functionality, thermal stability and surface area, respectively, of the newly synthesized MOF material. The solvent-free MOF material (1') was obtained by stirring the as-synthesized material in methanol for 24 h and then heated at 100 degrees C in vacuum. A systematic fluorescence study of 1' showed an ultrafast, highly selective turn-on response towards the lethal cyanide (CN-) ion. A 300-fold increment in fluorescence intensity was observed, which has not previously been reported for any probe for cyanide sensing. To check the selectivity of 1' towards CN- over other interfering anions, fluorescence sensing experiments were performed with 1' in the presence of a wide range of anions, none of which caused significant interference. The detection time for the probe 1' towards CN- was only 1 min, with a very low limit of detection (LOD) (0.28 mu M). A fluorescence study was carried out in different pH media to check its usefulness towards the sensing of CN- in a wide pH range. Naked-eye detection of CN- was achieved by a paper strip coated with MOF material, which showed promise for more realistic applications. The reversibility of the CN- sensor was demonstrated using trifluoroacetic acid as the proton source. Furthermore, we could utilize the probe to detect CN- in food and real water samples.