Isomeric Zinc(II) Triazolate Frameworks with 3-Connected Networks: Syntheses, Structures, and Sorption Properties

Two pairs of supramolecular isomers based on ternary zinc(II)/triazolate/X (triazolate = 3,5-dimethyl-1,2,4-triazolate (Hdmtz), X = HCOO−, F−) metal azolate frameworks, namely, [Zn(dmtz)(HCOO)]·H2O (MAF-X3, 1a), [Zn(dmtz)(HCOO)]·(1/6Me2NH)(1/4H2O) (MAF-X4, 1b), [Zn(dmtz)F] (MAF-X5, 2a), and [Zn(dmtz)F] (MAF-X6, 2b), have been synthesized via variations of the reaction conditions. The 3-connected Zn(dmtz) networks in 1a, 1b, 2a, and 2b can be described as rarely observed 4.82, 4.122, (8,3)-b, and 82.10-a, respectively. Besides the μ3-dmtz, tetrahedral and trigonal-bipyramidal/square-pyramidal coordination of the Zn ions are accomplished by monodentate formate and μ-F, respectively. While 1a and 2b are nonporous structures, 1b and 2a exhibits 1D nanotubular hydrophilic (d 3.2 Å) and hydrophobic (d 3.6 Å) channels, respectively. Thermogravimetric analysis shows that the stabilities of 2a and 2b are much better than those of 1a and 1b, which may be ascribed to different coordination numbers of zinc atoms. Moreover, 1b and 2a with different pore properties show selective sorption behavior.