Role of Temperature on Framework Dimensionality: Supramolecular Isomers of Zn3(RCOO)8 Based Metal Organic Frameworks

Three new anionic metal organic frameworks, [Zn1.5(FDA)2(Me2NH2)]·xG (1), [Zn3(FDA)4(Me2NH2)2xG (2), and [Zn1.5(FDA)2(Me2NH2)]·xG (3) (FDAH2 = 2,5-furandicarboxylic acid, G = guest), were synthesized solvothermally via a temperature tuning strategy. Compound 1, synthesized at 90 °C, has a two-dimensional (2D) sheet structure, while 2 and 3, synthesized at 120 and 160 °C, respectively, have three-dimensional (3D) structures. Compound 2 has alternating hydrophobic and hydrophilic channels with pore dimensions ∼4.3 × 4.4 Å2 and ∼5.6 × 6.2 Å2, respectively. Compound 3 has only one type of pore with dimensions of ∼5.3 × 6.2 Å2. All three compounds have eight connected Zn3(RCOO)8 nodes as building units and are anionic, with dimethyl ammonium cations present inside the channels to balance charge. Compounds 1, 2, and 3 are supramolecular isomers with general formula [Zn1.5(FDA)2(Me2NH2)]n.