A novel 2D metal–organic framework probe: a highly sensitive and visual fluorescent sensor for Al3+, Cr3+ and Fe3+ ions

Abstract

The development of metal–organic framework (MOF)-based fluorescent sensors in the detection of metal ions has attracted significant interest. In this study, a novel 2D MOF Tb-DBA was constructed using Tb³⁺ and 2′-amino-1,1′:4,1′′-terphenyl-4,4′′-dicarboxylic acid (H₂DBA) by a solvothermal method. Tb-DBA could detect Al³⁺, Cr³⁺ and Fe³⁺ ions rapidly, sensitively, selectively and reversibly. The detection limit is as low as the nM level. Tb-DBA displayed fluorescence enhancement in the presence of Al³⁺, Cr³⁺ and Fe³⁺ ions. Significantly, Al³⁺, Cr³⁺ and Fe³⁺ ions could be visually detected under UV light. Additionally, Tb-DBA could also act as an indicator for alkaline solutions when pH > 10. The detection mechanism was studied by ICP, EDS and PXRD tests. These studies illustrated that cation exchange proceeded between Tb-DBA and Al³⁺, Cr³⁺ and Fe³⁺ ions, which inhibited the energy transfer from DBA to Tb³⁺ and enhanced the π*–π transitions of DBA.