Two Stable Terbium–Organic Frameworks Based on Predesigned Functionalized Ligands: Selective Sensing of Fe³⁺ Ions and C₂H₂/CH₄ Separation

Abstract

To construct desired metal-organic framework (MOF) sensors, the predesigned functionalized ligands 2,5-bis(2',5'-dicarboxylphenyl)pyridine (<b>L-N</b>) and 2,5-bis(2',5'-dicarboxylphenyl)difluorobenzene (<b>L-F</b>) with pyridine- and fluorine-decorated tetracarboxylic acids were used, and two stable terbium-organic frameworks, H₃O[(Tb(<b>L-N</b>)(H₂O)₂]·2H₂O (<b>Tb-N</b>) and [Tb₃(<b>L-F</b>)₂(HCOO)(H₂O)₄]·6H₂O (<b>Tb-F</b>), have been synthesized. The structures of <b>Tb-N</b> and <b>Tb-F</b> contain 1D open channels, which are functionalized by pyridine N or F atoms, respectively. Both of them show intense fluorescence in water and exhibit excellent selectivity and sensitivity to Fe³⁺ ions. The effects of different functional group sites on the stability and fluorescence sensing performance of MOFs have also been studied. In addition, a gas adsorption study demonstrates that <b>Tb-N</b> is capable of adsorbing C₂H₂ over CH₄ selectively.