Zirconium Metal-Organic Frameworks Containing a Biselenophene Linker: Synthesis, Characterization, and Luminescent...

The bicyclic ditopic linker 2,2'-biselenophene-5,5'-dicarboxylic acid (HSpSp), specifically designed for metal-organic framework (MOF) construction, has been synthesized in good yield and fully characterized. The corresponding zirconium MOF (Zr-MOF) [Zr₆O₄(OH)₄(SpSp)_3.8Cl_4.4] (1; where missing linkers are replaced by chloride anions as shown by X-ray fluorescence and elemental analysis) is isostructural with its bithiophene and bithiazole analogues. Starting from 1, an extension of the biselenophene-based Zr-MOF family has been successfully achieved, exploiting the structural analogy of the five-membered heterocycles selenophene, thiophene, and thiazole. Thus, three mixed-linker MOFs containing variable amounts of different bis(heterocyclic) dicarboxylic acids have been prepared and fully characterized: the two double-mixed [Zr₆O₄(OH)₄(SpSp)_2.6(TpTp)_1.3Cl_4.2] (2; H = 2,2'-bithiophene-5,5'-dicarboxylic acid) and [Zr₆O₄(OH)₄(SpSp)₂(TzTz)_1.8Cl_4.4] (3; H = 2,2'-bithiazole-5,5'-dicarboxylic acid) materials, as well as the triple-mixed [Zr₆O₄(OH)₄(SpSp)_1.6(TpTp)_1.2(TzTz)_1.4Cl_3.6] (4) compound. The four MOFs are luminescent under UV irradiation, exhibiting emission wavelengths falling in the blue-green visible region, as observed for their constitutive linkers. These materials open new horizons in the preparation of porous luminescent sensors or multicolor emitters for light-emitting diodes.