Two coordination polymers (CPs), with chemical formulas {[Ni2(bpp)2(BT)(H2O)6] 1.5(EtOH) 1.5H2O}n (1) and [Zn(bpp)(BT)0.5]·5H2O (2) (bpp = 1,3-bis(4-pyridyl)propane, and BT4− = tetraanion of 1,2,4,5-Benzenetetracarboxylic acid), have been synthesized and structurally characterized by single-crystal X-ray diffraction methods. In compound 1, the coordination environments of two crystallographically independent Ni(II) ions are both distorted octahedral bonded to two nitrogen donors from two bpp ligands and four oxygen donors from one BT4- ligand and three water molecules. Both bpp and BT4− act as bridging ligands with bis-monodentate and 1,4-bis-monodentate coordination modes, respectively, connecting the Ni(II) ions to form a 2D layered metal-organic framework (MOF). Adjacent 2D layers are then arranged orderly in an ABAB manner to complete their 3D supramolecular architecture. In 2, the coordination environment of Zn(II) ion is distorted tetrahedral bonded to two nitrogen donors from two bpp ligands and two oxygen donors from two BT4− ligands. Both bpp and BT4- act as bridging ligands with bis-monodentate and 1,2,4,5-tetrakis-monodentate coordination modes, respectively, connecting the Zn(II) ions to form a 3D MOF. The reversible water de-/adsorption behavior of 1 between dehydrated and rehydrated forms has been verified by cyclic Thermogravimetric (TG) analyses through de-/rehydration processes. Compound 1 also exhibits significant water vapor hysteresis isotherms.

A three-dimensional (3D) polycatenation supramolecular network with chemical formulas, [Zn(bpp)(BDC)]·1.5H2O (1), (bpp = 1,3-bis(4-pyridyl)propane, BDC2- = dianion of terephthalic acid), was synthesized and structurally determined. In compound 1, the coordination geometry of Zn(II) ion is distorted tetrahedral, where its 2D undulated layered framework is constructed via the bridges of Zn(II) ions with bpp and BDC2− ligands. Adjacent 2D layers are arranged in a combined parallel and interpenetrated manner to complete its 3D polycatenation supramolecular architecture. Compound 1 shows a one-step dehydration process with the weight losses of 6.1 %, approximately equal to the weight percentage of losing 1.5 guest water molecules. The cyclic thermogravimetric analysis reveals that compound 1 shows reversible, sponge-like water de-/adsorption behavior during de-/rehydration processes. Compound 1 also exhibits significant water vapor hysteresis isotherm.