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JOURNAL OF SYNTHETIC CRYSTALS ›› 2022, Vol. 51 ›› Issue (8): 1370-1377.

• Research Articles • Previous Articles     Next Articles

Synthesis of a Barium Metal-Organic Framework and Its Crystal Structure and Fluorescence Property

ZHANG Wenqian1, SUN Wei2, CAO Duo1, NIU Yajie1, WU Wenrong1, WANG Dongfei1   

  1. 1. College of Pharmaceutical Engineering, Xinyang Agricultural and Forestry University, Xinyang 464000, China;
    2. College of Planning and Design, Xinyang Agricultural and Forestry University, Xinyang 464000, China
  • Received:2022-03-19 Online:2022-08-15 Published:2022-09-08

Abstract: Metal-organic frameworks (MOFs) have become a hotspot because of their unique structures and potential applications in the field of crystal engineering and material science. At present, most metal centers of MOFs are transition metals, while the group Ⅱ metals (alkaline earth metals) with special configurations have obtained relatively less attention. In this work, a novel three-dimensional (3D) Ba(Ⅱ)-MOF, [Ba(INO)2]n was synthesized by solvothermal method, with isonicotinic acid N-oxide (HINO) as organic ligand and barium chloride dihydrate (BaCl2·2H2O) as metal salt. The structure and properties of this Ba-MOF were characterized by single crystal X-ray diffraction, X-ray powder diffraction, infrared spectroscopy, elemental analysis, thermogravimetric analysis and fluorescence spectroscopy. Single crystal X-ray diffraction results show that [Ba(INO)2]n crystallizes in the monoclinic Cc space group, and the unit cell parameters a=1.636 14 (7) nm, b=1.126 35 (4) nm, c=0.742 40 (3) nm. The Ba(Ⅱ) center is nine-coordinated distorted three cap triangular prism geometry. The Ba—O one-dimensional (1D) chains in [Ba(INO)2]n are connected by type-B INO ligands to form a two-dimensional (2D) layer, and then extended by type-A INO ligands along four directions to form a 3D framework. However, interestingly, when the Ba—O 1D chains are directly connected by type-A INO ligands, a 3D microporous framework can be formed, while type-B INO ligands further support the 3D framework to form a solid and stable pillared structure. [Ba(INO)2]n shows good thermal stability. In addition, the solid-state fluorescence test shows that,[Ba(INO)2]n exhibits a maximum emission peak at 395 nm under the excitation of 330 nm ultraviolet light. It shows an obvious blue shift compared to the 437 nm maximum emission peak of HINO ligand, which is caused by the electronic transition between INO ligand and Ba(Ⅱ) metal center.

Key words: barium(Ⅱ) metal-organic framework, high coordination number metal geometric configuration, rod-packing structure, thermal stability, fluorescence property

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