Combination effect of ionic liquid components on the structure and properties in 1,4-benzenedicarboxylate based zinc metal–organic frameworks

Abstract

Two types of 2D [RMI]₂[Zn₃(BDC)₃X₂] (Type A) and 3D [Zn(BDC)(H₂O)] (Type B) (H₂BDC = 1,4-benzenedicarboxylate acid) compounds were synthesized with three kinds of 1-alkyl-3-methyl imidazolium halide ([RMI]X) ionic liquids. Type A is the primary structure model showing a (3,6) network. Type B can be obtained from [BMI]Cl, [AMI]Cl and [AMI]Br media, showing a 4,4-connected {4²·8⁴} network. The structure, TG, and fluorescence analyses demonstrate the combination effect of the RMI⁺ templating effect and X⁻ controlling the structure types. The boundary between Types A and B is from [PMI]Cl, via [BMI]Br, to [AMI]I as the reaction media. The decomposition temperatures of the compounds in Type A decrease with increased RMI⁺, while X⁻ anions exert the influence that compounds containing Br⁻ supply the highest thermal stability. Similarly, with increased RMI⁺, or X = I⁻, the compounds show red shifts compared to the emissions of the ligand.