A 3D photoluminescent Eu(iii)-MOF sensor supported by a tetracarboxylate ligand for the sensitive and selective detection of Cd2+ and o-nitrophenol

Abstract

A novel 3D luminescent metal–organic framework (MOF) denoted as [Eu(BTA)_0.5(H₂BTA)_0.5(H₂O)]_n (Cj-2) has been constructed from a π-conjugated ligand with a tetracarboxylate group, 1,2,4,5-benzenetetracarboxylic acid (BTA), via solvothermal synthesis. Structural analysis reveals that the Cj-2 framework is composed of tetranuclear secondary building units (SBUs) containing uncoordinated carbonyl groups which provide feasible recognition sites to interact with analytes. Cj-2 shows a trinodal (4,6,10)-connected 3D topological network consisting of tetranuclear SBUs. Cj-2 displays outstanding potential as a luminescent sensor for detecting o-NP and Cd²⁺ in DMF suspension, with remarkable sensitivity and selectivity through the luminescence quenching effect. Cj-2 displays excellent luminescence quenching behaviour in the presence of other competing interfering analytes and can be recycled at least four times for sensing o-NP and Cd²⁺. For Cd²⁺ ions, it is the host–guest interactions and for the nitroaromatic compounds, it is the competitive absorption of excitation energy and the electron transfer mechanism that are the probable mechanisms for such sensing processes. Moreover, visual fluorescent test papers based on Cj-2 were assembled and employed to selectively detect nitroaromatic compounds and metal ions. Based on the aforementioned results, Cj-2 can be considered as a potential luminescence sensor for detecting Cd²⁺ and o-NP.