Assembly of two new self-interpenetrating metal-organic frameworks with tunable luminescent properties

Abstract

Two newly isostructural Zn-MOFs, namely [Zn2(DMTDC)2(H2O)(TPT)]·4H2O (JOU-8) and [Zn2(DMTDC)2(H2O)(TPY)]·4H2O (JOU-9), have been solvothermally synthesized and characterized (H2DMTDC = 3,4-DiMethylthieno(2,3-b)thiophene-2,5-dicarboxylic acid, TPT = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine, TPY = 2,4,6-tri(pyridin-4-yl)pyridine). Single-crystal X-ray diffraction revealed that JOU-8 and JOU-9 displayed three-dimensional self-interpenetrating structure with a new type of (6,6)-connected topology. Further studies revealed that strong π-π interactions between conjugated ligand DMTDC and TPT/TPY leaded to the formation of ligand-to-ligand charge transfer, which not only extended the absorption band edge of MOFs but also induced new emission peaks. The emission peaks at 401 nm for JOU-8 and 402 nm for JOU-9 were derived from the ligands, while the emission peaks at 489 nm for JOU-8 and 499 nm for JOU-9 may be derived from the π-π interactions between DMTDC and TPT/TPY. Moreover, the emission peak intensity of JOU-8 and JOU-9 are tunable depending upon the excitation wavelength. Thus, both JOU-8 and JOU-9 were potential dual-emission materials. This work provides new clues for the preparation of entangled MOFs with tunable luminescent properties.