The Thermal Conversion Of Bismuth-containing Prussian Blue Analogues And The Applications Of Their Products

In recent years of materials research, as one kind of metal organic framework material, the applications of Prussian blue analogous (PBA) have been paid attention by part of scientific researchers. And as precursors, series of multifunctional metal oxides with morphology and structural diversity are obtained by their thermal conversion. In this work, we select one kind of bismuth-contained oxyacid salts and oxides as the target products, especially the BiFeO3 and Bi2O3. And followed, we study the thermal conversion process of Bismuth-containing Prussian blue analogous, and the applications of their products. Specific work is mainly divided into the following three aspects:1. Monocrystalline mesoporous metal oxide with perovskite structure: a facile solid-state transformation of Bi-Fe PBAIn this work, we get X-shaped sheets of Bi-Fe PBA by precipitation method at room temperature, while using sodiumcitrate (Sc) and polyvinylpyrrolidone (PVP) as moderator, bismuth nitrate and potassium ferricyanide as the reagent under acid condition. The precursor Bi-Fe PBA is a phase-pure mesocrystals with uniform X-shaped thick sheets, which characterized by XRD, SEM and TEM. Through the SEM image of samples with different reaction time, we can speculate that the Bi-Fe PBA mesocrystals is formed by non-classical crystallization involving superfast oriented attachment of nanoscale single-crystals. After calcinated at 400 ℃ for 120 minuntes, Bi-Fe PBA translated into pure BiFeO3 with perovskite structure successfully. The SEM and TEM display that the products is monocrystal with porous structure. As a photocatalyst on degradation of rhodamine B, BiFeO3 showed a good catalytic efficiency. It is worthly mentioned that compared to traditional solid state method, this kind thermal conversion reduces the synthesis temperature of BiFeO3 effectively. So the thermal conversion of Bi-Fe PBA to BiFeO3 has the potential commercial value for industrial production.2. A novel method to synthesize monodispersed porous La doped Bi-Fe PBA with unique dielectric response in the productBased on the synthesis methods of the first research system, we add different stoichiometric ratio of lanthanum nitrate in the acid solution of bismuth nitrate. The product is pure grain with orthogonal Cmcm structure characterized by XRD. SEM shows the morphology and structure of samples with different content of lanthanum is same, which is prismatic microparticle with rough surface. In air atmosphere, the BixLa1.x[Fe(CN)6] is calcinated under the condition of 400 ℃ for 120 min. XRD results shows that as the increase of the lanthanum doped, the crystal structure of pure phase BiFeO3 tend to translate from R3c structure to C222 structure. SEM and TEM show the calcinated product keep in line with the morphology of precursor and porous structure. As increasing of lanthanum doped ratio, magnetic of samples increased, which shows that the intrinsic magnetic moment of BixLa1-xFeO3 released as the changing of crystal structure. As one kind of typical perovskite metal oxide which can coexist in ferromagnetic and ferroelectricity at room temperature, the BixLa1.xFeO3 with porous structure showed unique performance in dielectric response.3. The thermal conversion of Bi-Co PBA to Bi2 - xCoxO3 with porous structure and its photocatalytic performance researchBy mixed the acid solution containing potassium hexacyanocobaltate and bismuth nitrate with stoichiometric ratio at room temperature for 6 h, phase-pure Bi-Co PBA is produced successfully. SEM shows that the Bi-Co PBA is uniform rectangular block microparticle with surface roughness. When calcined at 500 ℃ for 2 h in air atmosphere, the white Bi-Co PBA powder turn to black powder. It is identified as Bi2-xCoxO3 with high doping ratio (x≈0.5) by XRD and EDS. The high proportion doping amount is rarely reported in other literature. When characterized by ultraviolet-visible light absorption spectrum line, compare with the commercial Bi2O3, the absorption peak of Bi2-xCoxO3 is occurred a red shift, and it has an absorption in the whole visible light range. By compared with the commercial Bi2O3, Co-doping realized the magnetization of Bi2O3. The sample Bi2-xCoxO3 also shows a relatively good performance in the degradation effect of Rhodamine B.