The mixed-ligand strategy to assemble a europium metal-organic framework with a 2-fold-interpenetrated network

Highlights: • This paper reports a novel europium complex with a 3-D framework. • The 3-D framework features a 2-fold-interpenetrated network. • Diffuse reflectance spectroscopy reveals that it has a wide optical band gap. • It shows red photoluminescence which is assigned to the ⁵D₀ → ⁷F_J (Eu³⁺). • It has an antiferromagnetic behavior. - Abstract: A novel europium complex with the mixed ligands of 1-methyl-3,5-bis(4′-carboxy-phenyl)-1,2,4-triazole (mbcpt) and p-phthalic acid (pa), [Eu₂Cl₂(H₃O)₂(μ₄-mbcpt)₂(μ₄-pa)]_n (1), has been synthesized under the solvothermal conditions and structurally characterized by single-crystal X-ray diffraction. Complex 1 exhibits a three-dimensional (3-D) metal-organic framework. The 3-D open framework features a 2-fold-interpenetrated network. Solid-state diffuse reflectance spectroscopy uncovers the presence of a wide optical band gap of 3.56 eV, indicating that it is a wide band gap organic semiconductor material. Solid-state photoluminescence measurement reveals that complex 1 shows red light emission bands locating at 602, 611, 642 and 690 nm, which can be assigned to the ⁵D₀ → ⁷F_J (Eu³⁺) with the value of J = 1, 2, 3 and 4, respectively. Magnetic measurements reveal that complex 1 shows an antiferromagnetic behavior.