Four novel three-dimensional triazole-based zinc(II) metal-organic frameworks controlled by the spacers of dicarboxylate ligands: Hydrothermal synthesis, crystal structure, and luminescence properties

Four novel mixed-ligand metal-organic frameworks (MOFs), [Zn-5(mu(3)-OH)(2)(BTA)(2)(tP)(3)](n) (1), [Zn(BTA)(chdc)(0.5)](n) (2), [Zn(BTA)(ap)(0.5)](n) (3), and [Zn(BTA)(gt)(0.5)](n) (4) (BTAH = benzotriazole, H(2)tp = terephthalic acid, H(2)chdc = 1,4-cyclohexanedicarboxylic acid, H(2)ap = adipic acid, and H(2)gt = glutaric acid), have been synthesized by the reaction of zinc(II) chloride and BTAH with four different aromatic/aliphatic binary acids under similar hydrothermal conditions. All these compounds are fully structurally characterized by elemental analysis, IR, single-crystal X-ray crystallography, and the bulk new materials were further identified by X-ray powder diffraction. Their compositional stability and photoluminescence properties were further investigated to establish the structure-properties relationships. Structural analysis reveals that 1 is a scarcely reported eight-connected three-dimensional (3-D) self-penetrating MOF with pentanuclear zinc clusters as secondary building units (SBUs); 2 is a 3-D infinite network with empty 34-membered hexanuclear zinc(II) metallamacrocycle channels; 3 and 4 are 3-D meso-racemic coordination polymers with a one-dimensional Zn-BTA helix chain motif, in which alternative right- and left-hand helical chains are linked together via ap for 3 and gt for 4. The much higher compositional stability up to 436 degrees C and strong solid-state luminescence emissions suggest that 1-4 are good candidates for light emission materials.