Preparation And Properties Of Metal-organic Frameworks And Their Composite

Metal-organic frameworks(MOFs)consisting of metal ions or clusters connected by organic ligands have emerged as a novel class of nanoporous three-dimension framework materials.Compared with traditional microporous materials,metal-organic frameworks have possessed potential application value in many kinds of fields,such as adsorption,separation,chemical sensor,catalysis and so on,owing to their rich topological structure,high porosity,high specific surface area,tunable pore size and high chemical and thermal stability etc.With the increasingly environmental pollution,such as water pollution,poisonous gas and greenhouse gas emission,pollution abatement and new energy exploitation have been paid more attention,thus the studies of MOFs on environment and energy have become more important.In order to explore their application and optimize their properties,our researches have focused on the following aspects:Firstly,the representative HKUST-1 with highly water-stable property was synthesized by solvothermal method and characterized by XRD,SEM,TEM,FT-IR,TG,and its adsorption for uranyl ions was initially studied.The results indicated that the optimal adsorption conditions were confirmed,including the initial solution pH(at 6),dosage(0.03g)of adsorbents and the agitation time(2h).Langmuir adsorption isotherm was found to be more suitable to explain the adsorption of uranyl ions onto HKUST-1(all the correlation coefficients were larger than 0.99)and the adsorption kinetics data matched with the pseudo-second-order model.The thermodynamics of uranyl ions/HKUST-1 system indicated the spontaneous and endothermic nature of the process.The adsorption mechanism was supposed to combine physical adsorption with chemical adsorption.In all of the desorptive solutions,Na2CO3 possessed the best desorption yield.This work has verified the potential application value of metal-organic frameworks in uranium removal and provided a basis for research on the other MOFs materials in this field.Secondly,under the high reaction concentration and TEA-assisted method,MOF-5 with unique porous structure was synthesized by solvothermal method and characterized by XRD,SEM,TEM,N2 adsorption/desorption analysis etc.The results indicated that as-prepared MOF-5 possessed the structure combining the interpenetration with the mesopores includingintercrystalline mesopores.Compared with the reported MOF-5,its thermal stability and hydrogen-uptake capability were improved.The thermal decomposition temperature was 470? and the amount of hydrogen storage was 1.86 wt%.In addition,based on the basis,the functionalized multi-wall carbon nanotubes(MWCNTs)were introduced into the as-made MOF-5,and their effects on the structure and properties of the prepared MOF-5 were further studied.The results suggested that MWCNTs can further enhance the hydrogen-uptake capability,thermal and structural stability.Its thermal decomposition temperature was 495°C and the amount of hydrogen storage was 2.02 wt%.In addition,they have been stable in air condition(20%RH)for 6 days.This work offered the thought and method for more research on improvement of properties of the other MOFs materials.Thirdly,carried by the copper net,functionalized MWCNTs on the copper net were served as growth sites for MOF-5,and then MOF-5 film was successfully synthesized via the secondary growth method.In order to prepare the MOF-5/MWCNTs/Copper net composite film,Bi2O3/MWCNTs/Copper system was chosen to explore the technique and the two-step self-assembly method was developed.The composite film was characterized by XRD,SEM and optical microscope.The results showed that the composite film possessed high crystalline and compact texture.Compared with MOF-5/Copper net film,its structural stability was improved.After assembled with dye,it exhibited photoluminescence.This work demonstrated the application prospect of MOFs films as host materials in laser system.This work will provide a basis for research on expanding application of MOFs in adsorption and give a routine for optimizing the properties of the porous materials.