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

Three new anionic metal organic frameworks, [Zn_1.5(FDA)₂(Me₂NH₂)]·xG (1), [Zn₃(FDA)₄(Me₂NH₂)₂]·xG (2), and [Zn_1.5(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 Ų and ∼5.6 × 6.2 Ų, respectively. Compound 3 has only one type of pore with dimensions of ∼5.3 × 6.2 Ų. 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 [Zn_1.5(FDA)₂(Me₂NH₂)]_n.