Synthesis Of Metal-Organic Frameworks Materials For Pollutants Elimination From Solution

Metal-organic frameworks(MOFs)are a new class of porous materials which are composed of metal nodes and organic linkers.In virtue of vast surface area,high porosity,superior stability,multiple coordination sites and modifiable surface properties,MOFs have shown various potential applications,such as gas adsorption and storage,heterogeneous catalysis and pollutant elimination.In this study,we prepared a series of MOFs materials,including acetic acid-modulated Zr-MOFs(UiO-66),composite materials of POM and UiO-66,composite materials of m-phenylenediamine and UiO-66,composite material of m-phenylenediamine and Ni-Co prussian blue analogous(Ni-Co PBA),composite material of m-phenylenediamine and Fe-Co prussian blue analogous(Ni-Co PBA).Subsequently,the property of MOFs materials for removing contaminant from water was evaluated.The major results and conclusions of this study are as follows:1)Acetic acid-modulated synthesis of UiO-66 for adsorption of anionic dyeA series of UiO-66 were fabricated through a solvothermal method with acetic acid as modulator.The as-prepared samples were characterized by TEM,PXRD and nitrogen adsorption experiments to explore the effects of acetic acid addition on morphology,crystal structure and surface area of UiO-66.With increase of acetic acid addition(0 mL→18.4 mL AA),UiO-66 was changed from smaller intergrown nanocrystals(OmL)→ spherical nanoparticles(2.3mL→irregular octahedron(4.6mL→ regular octahedron(6.9mL,9.2mL)→irregular octahedron(11.5mL,13.8mL)→corner deficiency nanocrystals(16.1mL,18.4mL).The positions of the characteristic peaks were similar in the PXRD patterns of acetic acid-modulated UiO-66,indicating that the addition of acetic acid did not change the crystal texture of UiO-66.The nitrogen adsorption experiments shown that when upgrading the amount of acetic acid,BET surface area and total pore volume of UiO-66 increased significantly.The adsorption experiments indicated that UiO-66 exhibited high adsorption to anionic dye but low adsorption to cationic dye,and the adsorption capacities of U-OmL and U-6.9mL to OG were 204.7 mg/g and 246.7mg/g,respectively.2)Trichloroacetic acid-modulated synthesis of polyoxometalate@UiO-66 for selective adsorption of cationic dyesPOM@UiO-66 nanoparticles were fabricated by encapsulation of POM(K6P2W,8O62 polyoxometalate)into mesoporous UiO-66 metal organic framework through a solvothermal method with trichloroacetic acid as a modulator.The as-prepared samples were characterized by TEM,SEM,PXRD,TG,XPS,and EDX elemental mapping,and the successful combination of POM and UiO-66 was confirmed.Two cationic dyes,rhodamine B and malachite green,and one anionic dye orange G were employed to investigate the adsorption performance of POM@UiO-66.The adsorption data showed that the removal process of cationic dyes by POM@UiO-66 matched well with the pseudo-second-order model and Langmuir isothermal model.The resulting POM@UiO-66 nanoparticles exhibited high adsorption to cationic dyes but low adsorption to anionic dyes,and the adsorption capacities of rhodamine B,malachite green,and anionic dye orange G were 222.6,190.6 and 40 mg/g,respectively.Furthermore,the cationic dyes could be selectively removed from a cationic-anionic dye binary system.3)Synthesis of core-shell MOF@poly(m-phenylenediamine)particles for degrading organic pollutants by activating peroxymonosulfateMOF@poly(m-phenylenediamine)particles(MOF@PmPDs)with well-defined core-shell structure were prepared with UiO-66,Ni-Co PBA,Fe-Co PBA as inner core and m-PD as outer shell.Fe-Co PBA@PmPDs was selected as catalyst for the degradation of RhB by activating peroxymonosulfate(PMS).Catalysis experiments shown that Fe-Co PBA@PmPDs displayed excellent catalytic activity,achieving almost complete removal of 15ppm RhB at the reaction conditions of 0.1 g/L catalyst and 0.4g/L PMS.Cobalt ion dissolution experiments indicated that the Co2+ concentration of Fe-Co PBA and Fe-Co PBA@PmPDs were 0.54mg/L and 0.28mg/L,respectively,which were far below national emission standard(lmg/L).Cycling tests shown that the catalytic performance of Fe-Co PBA@PmPDs was gradually decreased.However,69%of RhB still can be removed after four successive cycling tests,indicating the good stability of Fe-Co PBA@PmPDs.Furthermore,Fe-Co PBA@PmPDs remained well-defined core-shell structure after catalysis experiment,only a small corner of PBA core dissolved into solution.