Design And Synthesis Of Heterometallic Organic Frameworks And Effects Of The Second Metals On Their Properties

Metal-organic frameworks（MOFs）are coordinated by metal bridging organic ligands with infinited extending 1D chain,2D layer or 3D network structure.Due to its structure and active site designability,high porosity,large specific surface area and other characteristics,it has great application potential in gas adsorption and separation,fluorescence sensing,electrochemical energy storage,catalysis and other fields.Heterometallic organic frameworks（HMOFs）can be obtained by introducing another metal into MOFs and making it participate in coordination.This introduction not only transforms the topological and pore structures of MOFs,but also tunes the electronic structures of pristine MOFs,optimizing their intrinsic properties,such as enhanced water stability,electrical conductivity,catalytic performance,luminescence,and porosity.The improvement of MOFs can increase its adsorption and separation performance for specific guests.However,it is still a very challenging work to specifically study the effect of the specific metal on the performance of MOFs.Based on the above research background,in this paper,5-（1H-tetrazol-5-yl）isophthalic acid（H₂L1）was selected to bridged the Pb（Ⅱ）ion,which has diverse coordination modes and high tolerance to various metals.Four examples of Pb-based HMOFs,and electrochemically active1,1’-ferrocene dicarboxylic acid（H₂L2）ligands were selected to construct a series of Fe-based HMOFs.Under the premise of controlling the structure consistency,the effects of different kinds of metal ions on the stability,fluorescence,and catalytic properties of the original single-metal MOFs were deeply explored.This article is divided into the following three chapters:In the first chapter,the concept and preparation of heterometallic complexes and their advantages compared with single metal complexes in application are briefly introduced.In addition,the current research and research progress on the properties of heterometallic complexes,as well as the significance of the topic of this paper,are also introduced.In the second chapter,a new monometallic MOF:[Pb（L）]_n（1）was synthesized using H₂L1.And the four isoreticular Pb-based HMOFs was constracted by introducing different metals,namely{[Pb M_0.5（L1）（H₂O）₂)·2H₂O}_n（M=Zn（2）,Cd（3）,Co（4）and Mn（5））.Compared to 1,the enhanced luminescence intensity of HMOFs 2 and 3 can be used as nitrobenzene sensors（the lowest detection limit can reach 0.13mm）;and HMOFs 4 and 5 can be used as excellent catalysts for CO₂ cycloaddition and the catalytic conversion efficiency of substrate with long chain substituent reached 99.0%at 80℃for 6 h.In the last chapter,a series of stable isoreticular MOFs/HMOFs were synthesized using H₂L2,namely[M（L）（bipy）]_n（M=Cu（1-Cu）,Co（1-Co）,Cu/Co（2-Cu_xCo_y））.The experimental results show that the thermal stability,band gap,and catalytic activity of MOFs are greatly changed with the introduction of different contents of the second metal.The test shows that2-Cu_0.32Co_0.68 has a good catalytic effect on OER reaction.When it was loaded on the nickel foam to drive the current density of 100 mA cm^-2,the required overpotential was 315 mV.And 2-Cu_0.86Co_0.14 had a good catalytic effect on photodegradation of Congo red,and the degradation rate of 60 ppm Congo red reached 99.9%after 60 min of photoreaction.