The Research Of Synthetic Method And The Control Of The Size Of Layer MOF Pillared By Keggin Polyoxometalates

Polyoxometalates (short for POMs) is a class of inorganic metal-oxygen clusters, it has awide research in catalysis, nanotechnology, biotechnology, materials science,etc because ofthe diversity of the composition and the structure. Metal-organic frameworks (MOFs) is aclass of compound made of metal ions and organic ligands, which tend to have high surfacearea and adjustable pore structure. The introduction of POMs to the MOFs produces thecrystalline porous materials based on polyoxometalates, which realizes the carrying ofpolyoxometalate and makes it possible to use in heterogeneous catalysis. While, somecorresponding properties will also be enhanced, even to get some new materials with newproperties when the size of the material is nanoscale.We first produced the compound1in hydrothermal conditions,{[Cu2(4,4’-bipy)4(H2O)4](SiMo12O40)(H2O)10}n, Through the analytical analysis of crystalstructure we found that each copper atom was coordinated by four nitrogen atoms from four4,4’-bipy and two Oxygen atoms from two water molecules, which forms a topologystructure of44, the polyoxometalate molecules selectively arranged between layer and layer,which formed a three dimensional space structure. In order to study the affect of the synthesisprocess to the size and morphology of the compound we tried to synthesis of compound1under conventional reaction conditions (room temperature, water system, or a mixed solventsystem).Through a lot of experiments we got the crystal of compound1in aqueous ethanolmixed solvent, the crystal size is about60nm determined by scanning electron microscopy.We successfully synthesized nano-sized compound2under normal conditions{[Cu2(4,4’-bipy)4(H2O)4](SiW12O40)(H2O)18}n（compoud2）which has a similar structurewith compound1. With the comparison of the XRD and IR of the single crystal reported inthe literature produced in hydrothermal condition, we found that the compound achievedfrom the two synthesis methods is the same kind of compound. By scanning electronmicroscopy (SEM) we determined the size of the crystals is approximately50~70nm...