Novel alkaline earth metal–organic frameworks with thiophene groups for selective detection of Fe3+

Abstract

Three new alkaline earth metal–organic frameworks (MOFs), namely [Mg₂(DMTDC)₂(DMF)₃(H₂O)₂]·2DMF·2H₂O (1), [Ca(DMTDC)(DMF)] (2) and [Sr(DMTDC)(DMF)] (3), have been synthesized under solvothermal conditions by using a thiophene-functionalized dicarboxylate ligand, 3,4-dimethylthieno[2,3-b]thiophene-2,5-dicarboxylic acid (H₂DMTDC). Single-crystal X-ray diffraction analyses demonstrate that the metal ion radii play an important role in coordination numbers and topologies, i.e., hexa-coordinated Mg²⁺ in 1 gives a two-dimensional layered framework with an sql net, while octa-coordinated Ca²⁺/Sr²⁺ in 2/3 exhibit a three-dimensional framework with lvt nets. All frameworks show a one-dimensional rhombus-shaped channel that is occupied by DMF and/or water molecules. Photoluminescence studies reveal that 1–3 can be used as fast-response fluorescence sensors for the sensitive detection of Fe³⁺ ions with favorable recyclability through fluorescence quenching.