Structural diversity of coordination polymers controlled by the metal ion as the sole reaction variable

Abstract

Three new coordination polymers based on 4,4′-(ethyne-1,2-diyl)dibenzoic acid (H₂edba) and 2,2′-bipyridine (bpy) ligands, namely, [Zn(edba)(bpy)]·xGuest (1), [Cu(edba)(bpy)]·xGuest (2), and [Co₃(edba)₃(bpy)₂]·3DMF·H₂O (3) (DMF = N,N-dimethylformamide), were synthesized under the same solvothermal conditions except for the use of different metal ions. Single-crystal X-ray analysis indicates that with the different coordination habits of Zn²⁺, Cu²⁺, and Co²⁺ ions, the resulting compounds feature coordination structures with different dimensionalities, namely, a 1D zigzag chain based on single-ion nodes in 1, a 2D sql layer based on dinuclear 4-connected nodes in 2, and a 3D sxb framework based on trinuclear 6-connected nodes in 3. In addition, after the removal of guest molecules, the 2D framework of 2 and the 3D framework of 3 are stable enough for CO₂ sorption with Langmuir surface areas of 440 cm² g⁻¹ and 542 cm³ g⁻¹, respectively. The present study serves as an example, in which the metal ion acts as the sole reaction variable, demonstrating the significance of the metal ion in the structural diversity of coordination polymers.