Structural characterization and solvent vapor sorption of two solvent-dependent Zn(ii) supramolecular architectures based on a flexible tripodal thioether-based pyridyl ligand and a dicarboxylate-based ligand

Abstract

Two solvent-dependent 3D supramolecular architectures constructed by a doubly-interpenetrating layered 2D MOF of [Zn₃(L¹)₂(L²)(Cl)₄(CH₃OH)₂]·6CH₃OH (1) and triply-interpenetrating 3D MOF of [Zn(L¹)(L²)(H₂O)]·2C₂H₅OH (2) (L¹ = 1,3,5-tris(4-pyridylsulfanylmethyl)-2,4,6-trimethylbenzene and L² = dianion of 2,5-dihydroxyterephthalic acid), were synthesized and structurally characterized using single-crystal X-ray diffraction method. In compound 1, there were two crystallographically independent Zn(II) ions with a distorted octahedral and a distorted tetrahedral geometries, respectively. L¹ acted as a bridge ligand with a tris-monodentate coordination connecting two Zn(II) (Zn(1) and Zn(2)) ions to form a one-dimensional (1D) polymeric chain, genertating a [Zn₂L¹₂] metallocycle as the building unit. Adjacent chains were then connected via the bridge of Zn(II) and L² with a bis-monodentate coordination mode to form a two-dimensional (2D) layered MOF. Two 2D layers mutually interpenetrated via the L² ligands penetrating into the [Zn₂L¹₂] metallocycle rings to genetrate a 2D doubly-interpenetrating network. In 2, the Zn(II) ion was six-coordinate bonded to three nitrogen donors of three L¹ and three oxygen donors of two crystallographically independent L² and one H₂O molecule to form a distorted octahedral grometry. L¹ acted as a bridge ligand with a tris-monodentate coordination connecting Zn(II) ions to form a 2D honeycomb-like layered framework. Adjacent 2D layers were mutually connected via the bridge of Zn(II) and L² with a bis-monodentate coordination mode to form a three-dimensional (3D) MOF. The much larger intraframework spaces were then occupied by the other two 3D crystallographically identical networks but independent to form a 3D triply interpenetrating supramolecular architecture. The reversible solvent vapor ad-/desorption behaviors were investigated by cyclic de-/rehydration TG analysis and the water vapor ad-/desorption isotherms of 1 and 2 were studied in detail.