Synthesis And Application Of Iron Oxide Functional Porous Materials

Porous materials are important research content of material science. Expanding the scope from pure porous materials to hybrid materials, by combining the porous materials with other functional components, it significantly broadens the field of material capability. Iron oxides, which possess different types and properties, are common functional component. The dispersion and catalytic activity of α-Fe2O3 nanoparticles can be improved after combining with porous materials. The γ-Fe2O3 and Fe3O4 possess strong magnetic properties. The composite, which is composed with magnetic iron oxide and porous materials, can be rapidly located and collected by external magnetic field. In this paper, different methods are adopted to prepare a series of iron base porous material using iron oxide as functional component.Novel hierarchical iron-containing MFI zeolite microspheres composed of oriented-assembled nanosheet were prepared through a one-step hydrothermal crystallization without a mesoporous template agent. After adding a certain amount of glucose into the synthetic system, the obtained samples possess uniform diameters about 4 to 5 μm, a hierarchical porous structure, a high surface area (502 m2/g), and well-dispersed ultrafine α-Fe2O3 nanoparticles. The glucose has an important effect on the iron species and crystallinity of the zeolite. Moreover, the obtained zeolite microspheres show an excellent catalytic performance in the photocatalytic degradation of phenol. COD removal rate of phenol solution reaches 100% after 1.5 hours. This catalyst shows a good stability and can maintain the catalytic performance after multiple cycles. This synthesis opens up routes for the in situ preparation of other functional porous materials.The core-shell magnetic mesoporous composite (γ-Fe2O3/nSiO2/mSiO2) was synthesized by a sol-gel method using cetyltrimethylammonium bromide as structure-directing agent. The composite possess very strong magnetization, high surface area, large pore volume, and uniform accessible mesopores. The γ-Fe2O3/nSiO2/mSiO2 is composed of a magnetic γ-Fe2O3 core and two shells of silica. The inner non-porous silica shell prevents the magnetic core from contacting with outside solution. The outer mesoporous silica shell could be amine functionalized, and presented positive charge under acid condition. Thus the negatively charged dichromate anions can be adsorbed on the composites through electrostatic interaction. The adsorption of dichromate anions fit well by Langmuir isotherm and the maximum adsorption capacity reaches to 1.03 mmol Cr/g adsorbent. More importantly, the adsorbent can be easily separated and recycled from the solution by adding an external magnetic field.A new type of magnetic core-shell structure MOFs composite (Fe3O4/IRMOF-3) was successfully prepared by a facile mixed solvothermal method. Fe3O4 nanoparticles and polyvinylpyrrolidone (PVP) are magnetic core and promoter, respectively. Fe3O4 nanoparticles are encapsulated completely inside the MOF matrix. PVP not only functionalizes as the stabilizers to make the Fe3O4 nanoparticles well dispersed but also provides the affinity to IRMOF-3 precursors onto the Fe3O4 nanoparticles surfaces. The composite possess high crystallinity, porosity characteristic, rapid magnetic response and excellent stability. The obtained Fe3O4/IRMOF-3 exhibited good catalytic performance in the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate. The conversion of ethyl cyanoacetate reaches 98.3% after 4 hours. The catalyst can also be quickly separated and reused for many times.