Assembly of two novel coordination polymers constructed from metal-organic framework and Keggin-template

Two new Keggin polyoxometalate (POM)-based compounds combined copper metal complexes have been synthesized under hydrothermal conditions: {[CuI(bipy)2·(H2O)2]4}·{[SiW12O40]2}·{(H2bipy)2(bipy)2}·8H2O (1) (bipy = 4,4′-bipyridine) and {CuI(bipy)2·(H2O)2}·{CuI(bipy)2}[H2SiW12O40]·20H2O (2), and structurally characterized by elemental analysis, IR spectra, EPR, TGA and single crystal X-ray diffraction. Two compounds are all based on [SiW12O40]4− Keggin building block and synthesized under the same reaction condition, only different pH values. The copper complex cations of compound 1 and 2 construct covalently 2D square grid structure, furthermore, the 2D square grids are held together into a three-dimensional supramolecular network through hydrogen-bonding interactions, whereas Keggin anions are sited in 3D square grid channels alternately. The results show that the pH value of the reaction system plays a crucial role in structural control of self-assembled processes.