A fluorescent Eu(III) MOF for highly selective and sensitive sensing of picric acid

A metal-organic framework [Eu3L3(CH3COO)(2)(H2O)(2)((3)-OH)]center dot 3DMF, (EuL, H2L=9H-carbazole-2,7-dicarboxylic acid, DMF=N,N-dimethylformamide) has been synthesized under solvothermal conditions and structurally characterized. In EuL, Eu6O8 clusters are four-bridged by carboxylates to form parallel-aligned Eu-O-C chains, which are further linked by the carbazole moieties of L2- ligands to form the three-dimensional framework with rhombic channels. The EuL material with characteristic emission of Eu3+ ion exhibits significant luminescence quenching response for picric acid (PA) and the linear Stern-Volmer plot was observed in the concentration range of 0.05-0.15 mM with K-sv of 98074 M-1. As far as we know, this K-sv is among the highest values for COFs and MOFs in detection of PA. The excellent anti-interference ability and repeatability were also verified by experiments. Lastly, we investigated the luminescence quenching mechanism in the EuL sensing system.