Highly selective acetone fluorescent sensors based on microporous Cd(II) metal-organic frameworks

Solvothermal reaction of Cd2+ ions and a hexavalent carboxylic acid (H6L) afforded a Cd(II) metal organic framework (Cd-MOF), namely {[Cd-3(L)(H2O)(2)(DMF)(2)]center dot 5DMF}(n) (1). Its structure consists of trinuclear Cd-II building units, which are further bridged by the carboxylic ligand, resulting in a 4,4-connected topological net (sra). By introducing a rigid N-donor ligand 1,4-bis(1-imidazolyl)benzene (dib), a new Cd-MOF (2) {[Cd-3(L)(dib)]center dot 3H(2)O center dot 5DMA}(n) was isolated, in which the coordinated sites of solvent molecules in 1 were completely replaced by dib. The resulting trinuclear Cd-3 subunits are further bridged into a two-fold interpenetrating network with DMA and water molecules located in the void space. The luminescent properties of the two microporous Cd-MOFs dispersed in different solvents have been investigated systematically, demonstrating unique selectivity for the detection of acetone via a fluorescence quenching mechanism. Their luminescence intensities decreased to 50% at an acetone content of 0.3 vol% and were almost completely quenched at a concentration of 1.0 vol%, thus, they can be considered as excellent potential luminescent probes for the detection of acetone.