Highly selective acetone fluorescent sensors based on microporous Cd(ii) metal–organic frameworks

Abstract

Solvothermal reaction of Cd²⁺ ions and a hexavalent carboxylic acid (H₆666666L) afforded a Cd(II) metal organic framework (Cd-MOF), namely {[Cd₃(L)(H₂O)₂(DMF)₂]·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) {[Cd₃(L)(dib)]·3H₂O·5DMA}_n was isolated, in which the coordinated sites of solvent molecules in 1 were completely replaced by dib. The resulting trinuclear Cd₃ 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.