Vapochromic Luminescence of a Zirconium-Based Metal-Organic Framework for Sensing Applications

For the integration of responsive molecular units into chemically stable metal organic frameworks (MOFs), the luminescent ligand 9-fluoreneone-2,7-dicarboxylic acid (H2FDC) was utilised in a reaction with Zr4+. The resulting framework has fcu topology and is permanently porous with a BET surface area of 1428 m(2) g(-1). The MOF shows guest-responsive fluorescent properties and is therefore suitable for application in sensing of solvent vapours. Saturated vapours of non-polar aromatic and non-aromatic compounds can be distinguished on the basis of their shifts in the fluorescence emission peak. Polar solvents are also distinguishable, whereas aprotic solvents induce a hypsochromic and protic solvents a bathochromic shift. Furthermore, different alcohols can be distinguished from each other. In the case of water, the significant dependence of the emission wavelength on the concentration demonstrates the potential of the MOF as a humidity sensor.