Preparation,Microstructure Control And Performance Study Of Metal-Organic Framework (ZIF-67) Materials

Zeolite Imidazolate Frameworks（ZIFs）are very attractive subclass of Metal Organic Frameworks（MOFs）materials.With superb characteristics of high specific surface area,adjustable pore size,ultra-high porosity,the good chemical and thermal stability,the ZIFs were widely used in the fields of adsorption and separation,catalysts,wastewater treatments and so on.It has scientific researches and practical application values.The current researches mostly focus on some special morphologies to ZIFs.However,the research on the influence of preparation methods and synthesis conditions on the crystal morphology,structure and properties is relatively lacking.Therefore,it is imperative to explore the crystal synthesis regularities and obtain controllable regulation strategies of ZIFs.This paper was mainly about research of ZIF-67 on the synthesis,microstructure regulation and performance to establish a link between microstructures and properties.The following are the main contents and conclusions of the full text:1.There were three methods used to synthesize ZIF-67.The effects of preparation methods and process conditions were systematically investigated on ZIF-67 of morphology,structure,particle size,etc.The results showed that:（1）the Aqueous Phase Method:ZIF-67 was synthesized at 1:32 of the ratio.The structure directing agent of methanol had promoted the phase transition process from two-dimensional ZIF-L to three-dimensional ZIF-67.ZIF-67 was obtained at the theoretical ratio（1:2）with TEA.（2）the Methanol Phase Method:The optimal conditions of ZIF-67 were 200 mL methanol solvent,1:8 of the ratio,500 r·min^-1 of stirring speed,180 min of reaction time and cobalt nitrate as the cobalt sources.Increasing the amount of organic solvent or organic ligands helped to synthesize ZIF-67 with high crystallinity and small size.ZIF-67,produced from cobalt sulfate,was spherical with the size of less than 1μm and slightly poor crystallinity.（3）the Solvothermal Method:When the synthesis parameters were 115℃,24 h,and 1:8 of the ratio,ZIF-67 had strong crystallinity,uniform size,and good dispersibility.The product of 1:2 was ball-shaped flower,and as the amount increases of TEA,the ball flower disappears to form nanoparticles of ZIF-67.The polymers had the different self-assembly processes on the different metals and organic ligands.Therefore,the morphology and structure were diverse.2.Zn（Ⅱ）-and Cd（Ⅱ）-doped ZIF-67 were prepared.The effect of metal doping on the phase and microstructure of ZIF-67 was investigated.Then,their adsorption performance was determined by dye wastewater of methyl orange（MO）.The results showed:the metal was successfully doped into the ZIF-67 lattice without changing its phase structure but reducing crystallinity.ZIF-67 of Zn-doped did not change the crystal structure significantly,but increasing the amount of Cd maded the crystal finally football-like polyhedron.When the metals were doped with different organic ligands,the crystal structure of the products changed.The three ZIFs materials showed well adsorption performance for MO.The maximum adsorption capacities of ZIF-67,Zn_0.3Co_0.7-ZIF-67 and Cd_0.4Co_0.6-ZIF-67 were 749.10 mg·g^-1,409.58 mg·g^-1,and722.84 mg·g^-1 respectively.They were consistent with quasi-second-order kinetics and Freundlich adsorption isotherms.3.The composite photocatalytic material of TiO₂@ZIF-67 was synthesized by Wet-chemical methods.The micro-analysis method was used to investigate the loading state of TiO₂,and the photocatalytic performance of TiO₂@ZIF-67 was also explored.The results showed that:when the load ratio was 1:2,it could reach equilibrium in 120 minutes under direct light,and the decolorization rate of MO was as high as 84%.When pH=3-5 or the amount of adsorbent was 20 mg,the decolorization rate was 100%.Increaseing proportions of TiO₂,the decolorization rate increased.The effect of the TiO₂@ZIF-67 was the best on decolorization performance.