Two-in-one: Proton-conductive and luminescence properties of one strontium(II)-organic framework bearing imidazole dicarboxylate

Abstract

Despite the current surge in the production of metal-organic frameworks (MOFs) by crystal engineering, more structurally diverse MOFs must be developed and prepared for the study of their application properties and structural stability. Herein, one novel two-dimensional MOF, [Sr(μ5-p-FPhHIDC)(H2O)]n (1) was solvothermally constructed and structurally characterized by adopting an organic linker, 2-(4-fluorophenyl)-1H-imidazole-4,5-dicarboxylic acid (p-FPhH3IDC), in which the [SrO9] tetrakaidecahedrons were joined by the organic linkers to constitute a beautiful grid structure. The remarkable fluorescence characteristics and proton transfer are due to the strong coordination between the organic ligands and the central metal ions in the framework of 1, as well as the carboxylic acid and coordination water molecules carried on the framework. Extensive tests demonstrated that, at relative humidity of 75–98 %, this MOF displayed a specific proton conductivity (10−7-10−5 S/cm) and significant room-temperature solid-state fluorescence (λem = 406 nm). Proton conduction and luminescence mechanisms were also conjectured. This study is a helpful resource for creating MOF materials with a range of application-specific properties.