Synthesis, structure and fluorescent property of Zn-MOF with high stability based on mixed ligands

A zinc(Ⅱ) coordination polymer Zn₂(L)₂(bpy)_1.5(H₂O)₃∙4H₂O_n was synthesized hydrothermally with 5-(2-acetoxy-propionylamino)-isophthalic acid (H₂L), 4,4'-bipyridine (bpy) and zinc nitrate. The complex was characterized by elemental analysis, infrared spectroscopy, X-ray single crystal and powder diffraction diffraction. The complex crystallizes in triclinic system, P-1 space group, and the cell parameters are a = 1.000 74(4) nm, b = 1.273 23(6) nm, c = 1.820 04(8) nm, α = 110.164(4)°, β = 100.484(4)°, γ = 98.060(4)°, V = 2.088 20(17) nm³. The central ion Zn(Ⅱ) has two configurations of twisted tetrahedron and triangular bicone. Zn(Ⅱ) ions are bridged with the aromatic polycarboxylate ligands to form a one-dimensional chain, and the two adjacent chains are connected by auxiliary ligand bpy to form a ladder-like double-stranded structure, and finally a three-dimensional supramolecular structure is constructed through hydrogen bonds. Besides, thermal stability and fluorescent property of the complex were tested by thermogravimetric analysis and solid-state fluorescence, respectively. The results show that the complex has good thermal stability and strong fluorescence emission performance.