Two Stable Terbium–OrganicFrameworks Based on Predesigned Functionalized Ligands: SelectiveSensing of Fe 3+ Ions and C 2 H 2 /CH 4 Separation

To construct desired metal–organic framework (MOF) sensors, the predesigned functionalized ligands 2,5-bis(2′,5′-dicarboxylphenyl)pyridine (L-N) and 2,5-bis(2′,5′-dicarboxylphenyl)difluorobenzene (L-F) with pyridine- and fluorine-decorated tetracarboxylic acids were used, and two stable terbium–organic frameworks, H3O[(Tb(L-N)(H2O)2]·2H2O (Tb-N) and [Tb3(L-F)2(HCOO)(H2O)4]·6H2O (Tb-F), have been synthesized. The structures of Tb-N and Tb-F 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 Tb-N is capable of adsorbing C2H2 over CH4 selectively.