Hydrothermal Synthesis and Structural Characterization of Novel Zn−Triazole−Benzenedicarboxylate Frameworks

Three new metal−organic coordination polymers were synthesized hydrothermally using Zn2+ ion, 1,2,4-triazole, and 1,4-benzenedicarboxylic acid (BDC): Zn5(H2O)2(C2H2N3)4(C8H4O4)3·3.9H2O (1), Zn2(C2H2N3)2(C2H3N3)(C8H4O4)·2.5H2O (2), and Zn4(H2O)2(C2H2N3)4(C8H4O4)2·14H2O (3). Their crystal structures were determined by single-crystal X-ray diffraction. Their thermal properties were examined by thermogravimetric analysis. Structure 1 crystallizes in the monoclinic P21/n space group with a = 10.192(2) Å, b = 17.764(4) Å, c = 24.437(5) Å, β = 91.19(3)°, and V = 4423.3(15) Å3. Structure 2 crystallizes in the triclinic P1̄ space group with a = 7.797(2) Å, b = 10.047(2) Å, c = 13.577(3) Å, α = 110.18(3)°, β = 105.46(3)°, γ = 93.90(3)°, and V = 947.0(3) Å3. Structure 3 crystallizes in monoclinic P21/n space group with a = 13.475(3) Å, b = 26.949(5) Å, c = 13.509(3) Å, β = 95.18(3)°, and V = 4885.7(17) Å3. In structure 1, the units of the triazole−Zn polyhedra are linked by BDC in a zigzag fashion to create the stacking of phenyl groups along the a axis. In structure 2, both triazole and BDC bridge Zn polyhedra in the (011) plane, resulting in the eight-membered channels along the a axis. In the case of structure 3, the BDC links the Zn polyhedra along the b axis to form a pillared open framework. This structure is the most porous of the compounds presented in this work.