Synthesis And Application Of Magnetic Porous Composite Derived From Metal-organic Framework

Polycyclic aromatic hydrocarbons?PAHs?are one of classes of persistent of organic pollutiants?POPs?,which are notorious for their toxic,mutagenic and carcinogenic effects.Besides,they are tend to accumulate easily in biological body,which are subject to long time retention and extremely difficult to decompose.However,PAHs exist widely in the environmental aqueous solutions with low concentration.How to effectively achieve their enrichment and determination is still a challenge.It is of great importance to develop such methods with simple operation while environmentally benign.Metal-organic frameworks?MOFs?are being paid more and more attention due to their structure diversity,tunable pore size and great surface area,which were synthesized by assembling metal ions and organic ligands.MOFs have been used in variety of applications such as adsorption,separation,drug delivery and catalysis.Novel multi-functional composites can be obtained by controllable combination of MOFs and magnetic materials,which exhibit new properties that can be used to the absorption of the pollutants in environment.We synthesized magnetic porous composite derived from metal-organic framework,which could be used for the adsorption of persistent organic pollutants and malachite green dye.The main contents are summarized as follows:1.A green non-toxic composite material MIL-100?Fe?was pyrolysis carbonized under different temperatures.Then,the structure and properties of the products was studied.The results revealed that the carbonized products under different temperatures still keep the octahedral structure of original MOF.Besides,with the increase of pyrolysis temperature,the original smooth surface became rough,the magnetic nanoparticles even adhered to the surface.The sizes of nanopaticles increasing with the increase of temperature until the MOF collapsed into a magnetic porous composite.We also found that the composition of product changed under different pyrolysis temperature.In the higher temperature,the product is magnetic and porous,while in the lower temperature,the product is only partly magnetized and others still retain the original structure of MIL-100?Fe?.Compared with previously reported methods,our method is simpler and easier.2.Magnetic MOF?M-415?was obtained at low pyrolysis temperature,which could be used as an absorbent in magnetic solid-phase extraction to absorb polycyclic aromatic hydrocarbons.Then,studied the effect of adsorption time,absorbent quality,ion effect,solution acidity and eluent on the extraction efficiency of PAHs and the optimal experimental conditions were selected.Such extraction in combination with gas chromatography gave the detection limits of 6.2²0.8 ng L^-1 and the quantitation limits of 13.1³8.2 ng L^-1 for the PAHs and the RSDs analyses of intra-and inter-day are in the range of 1.7%³.7%and 5.1%³.7%respectively.The adsorption properties of different products were also studied.We found that the adsorption performance of M-415 is the highest due to both magnetic and MOF characteristics of material under 415oC.We also use as-prepared materials successfully for detection of polycyclic aromatic hydrocarbons in actual water samples.3.The MIL-100?Fe?pyrolysised at 700oC and obtained the product M-700,which was used to adsorb malachite green?MG?dye and studied the adsorption behavior.The adsorption of MG on M-700 is well described by the pseudo-second-order kinetic model,which reveals a chemisorption mechanism.The adsorption isotherms of MG on M-700 followed the Langmuir model.And the adsorbent has a higher adsorption capacity for malachite green dye.The adsorption of MG on M-700 is spontaneous and endothermic.As increase of the temperature,the adsorption quantity increases.Generally,this as-prepared composite is a good adsorbent for reomoving of dyes with high adsorption capacity and good reproducibility.