A Complex Based on a CuII–Schiff-Base Complex and POM-MOF Chain: Synthesis, Structure and Proton Conductivity

Graphical A 3D metal–Schiff-base–POM-MOF has been constructed by combining in situ two traditional building blocks, a metal–Schiff-base and POM-MOF, and its structure was determined by single-crystal X-ray diffraction. Due to the bonding of H 2 O to otherwise open coordination sites on Cu 2+ ions, it shows good proton conductivities of 10 –5 –10 –4 S cm –1 in the temperature range of 25–100 °C under 98 % RH. A metal–Schiff-base–POM-MOF, {[Cu 3 (L) 2 (H 2 O) 4 ] [Cu(dmf) 4 (SiW 12 O 40 )] · 9H 2 O} n {L = N , N′ -bis[(2-hydroxy-3-methoxyphenyl)methylidene]hydrazine hydrate}, has been synthesized in situ from [SiW 12 O 40 ] 4– , Cu 2+ and L in an H 2 O/dmf/CH 3 OH/CH 3 CN mixture at room temperature, and the product was characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis. X-ray diffraction analysis revealed that the title complex presents a 3D network constructed from Cu II –Schiff-base cations, 1D POM-MOF chains and solvent water molecules. Its water vapour adsorption isotherm at room temperature and pressure shows that the water vapour adsorbed by the complex is 51.67 cm 3 g –1 at the maximum allowable humidity, which corresponds to 7.1 water molecules per unit formula. In addition, it exhibits good proton conductivity (>10 –4 S cm –1 ) at 100 °C in the relative humidity range 35–98 %. The corresponding activation energy ( E a ) of conductivity was estimated to be 0.32 eV.