Research On Synthesis, Characterization And Catalytic Properties Of Keggin Type Polyoxometalates Compounds Based On Pyrimidine And Triazole

In this paper, with Keggin-type polyoxometalates as the basic building blocks, five novel organic-inorganic hybrid complexes have been successfully synthesized using N/O-donor organic ligand by hydrothermal method. All the complexes have been characterized by IR, UV-vis, FL,TG-DTA, CV and single-crystal X-ray diffraction. And test their gas-phase catalystic properties for eliminating methanol and other organic pollutants.In addition, four different bismuth catalysts have been synthesized with high photoresponsive bismuth salts and POMs. Their photocatalytic performance of degradation of Rh B, methyl orange, methylene blue pollutants has been explored.1. Two new inorganic-organic hybrid complexes constructed from phosphotungstic acid and N-containing ligand 2-aminopyridine and3-methylpyridine have been synthesized under hydrothermal conditions.The formula of two complexes are(C5H7N2)3(C5H6N2)3(PW12O40)·2H2O(1),(C6H8N)3(C6H7N)(PW12O40)·9H2O(2). Crystal data of complex 1:Monoclinic system, P2(1)/n space group, a=13.3371(7) ?, b=22.5278(12)?, c=21.8442(11) ?, α=90 °, β=115.880(3) °, γ=90 °, V=5905.0(5) ?3, Z=4.Crystal data of compound 2: Monoclinic system, P2(1)/n space group,a=12.0380(9) ?, b=20.1622(15) ?, c=26.2208(18) ?, ?=90 °,?=110.421(3) °, ?=90 °, V=5964.2(8) ?3, Z=4. These complexess exhibit good catalytic activity for catalytic oxidation of methanol over a continuous-flow fixed-bed micro-reactor, when the initial concentration of methanol is 5.37 g·m-3, and flow rate is 4.51 m L·min-1at 150 °C. 0.2 g complex 1 as the catalyst can eliminate methanol completely, while complex2 also can eliminate methanol thoroughly when the temperature is 175 °C.2. Two new inorganic-organic hybrid complexes constructed from phosphotungstic acid and N-containing ligand 1,2,4-Triazole have been synthesized under hydrothermal conditions. The formula of two complexes are(1,2,4-C2H6N3)·(PW12O40)·2H2O(3),(1,2,4-C2H6N3)·(PMo12O40)·2H2O(4). Crystal data of complex 3: hexagonal system, R-3 space group,a=17.9121(3) ?, b=17.9121(3) ?, c=24.3741(6) ?, α=90 °, β=90 °, γ=120 °,V=6772.5(2) ?3, Z=6. Crystal data of complex 4: hexagonal system, R-3space group, a=17.7657(2) ?, b=17.7657(2) ?, c=24.3713(6) ?, ?=90 °,?=90 °, ?=120 °, V=6661.5(2) ?3, Z=6. The organic ligands are interconnected via hydrogen bonds and π-π stacking which bring about“pores” in whole structure. Polyanions fill in the middle of those “pores”forming three-dimensional network. Complex 3 and 4 exhibit good catalytic activity of catalytic elimination of methanol in gas phase, when the initial concentration of methanol is 2.86 g·m-3, and flow rate is 4.15 m L·min-1 at100 °C, the elimination rate of methanol is 60.33% over 0.2 g complex 3;when the initial concentration of methanol is 2.15 g·m-3, and flow rate is4.15 m L·min-1 at 100 °C, the elimination rate of methanol is 84.27% over0.2 g complex 4..3. One novel organic-inorganic hybrid supramolecular compound(3-C6H6NO2)5·(C5H5N)·(Si W12O40)2·(H2O2)·10H2O(5) constructed by tungstosilicate anion and 2,3-pyridinedicarboxylic acid via intermolecular forces. Crystal data of complex 5: Monoclinic system, P2(1)/n space group,a=22.018(2) ?, b=22.778(3) ?, c=24.226(3) ?, α=90 °, β=114.532(2) °,γ=90 °, V=11054(2) ?3, Z=4. Complex 5 exhibits a good catalytic activity of catalytic elimination of methanol in gas phase, when the initial concentration of methanol is 3.65 g·m-3, and flow rate is 5.12 m L·min-1at170 °C, the elimination rate of methanol is 93% over 0.2 g complex.4. There are four catalysts Bi2WO6, Bi2 Mo O6, Bi PW12O40 and Bi PMo12O40 have been synthesized by hydrothermal or co-precipitation method and characterized by IR, UV-vis, FL, SEM and X-ray power diffraction. It is explored that relationship of catalytic performance of catalysts and preparation conditions, calcination temperature, and different substrates. The best degradation of 100 m L 4 mg·L-1Rh B can achieve 98.1%when the W/Bi molar rate is 1:2 over the unbaked Bi2WO6 catalyst which also has a certain catalytic effect for degrading Rh B, helianthin B and methylthionine chloride. The bismuth tungstate and bismuth molybdatecatalysts have a good catalytic effect for degrading Rh B, helianthin B and methylthionine chloride as well. The catalytic performance of phosphomolybdate bismuth catalytic is poorer.