| Metal-organic frameworks(MOF)are high porosity,specific surface area porous coordination network structures constructed from inorganic and organic structural units based on the principles of framework chemistry.The easily distorted nature of metal coordination spheres,the flexibility of the ligands,combined with the large size voids inside the porous structure,endow MOF with a wealth of physical and chemical exogenous factors to induce dynamic structural changes.Dynamic porous MOF are useful for the systematic study of interesting host-guest chemical behaviour such as adsorption of different guests,self-modulation of structural response,and post-synthetic structural transformations.In this thesis,we have constructed several examples of dynamic structural MOF with high porosity and systematically investigated their solvent substitution,activation condition optimization,gas adsorption,liquid phase organic dye trapping and gas/liquid phase iodine trapping behaviours;we have comparatively investigated the stability and adsorption modulation effects of different classes of metal active sites;we have explored the preparation of functional amorphous materials based on post-synthetic metal ion substitution and postsynthetic ordered-disordered transformation of MOF hosts.This thesis covers the following main topics:Chapter 1 is just an introductory chapter,which focuses on the development of MOF and a range of functional applications,highlighting the importance of the classification of MOF activation methods,metal sites and post-synthetic modifications of MOF.Chapter 2 studies the construction of highly porous and flexible MOF based on H2tzba,and their multi guest response to dynamic chemical and post-synthetic structural transformations.The monometallic 3D structured MOF-(Me2NH2)[Ni3(μ3OH)(tzba)3(H2O)3]·8DMF(compound 1),and the NiMn,NiZn bimetallic doping-induced 2D structured MOF-[Ni1.4Mn1.6(tzba)3(H2O)6]·9DMF(compound 2),[Ni2.3Zn0.7(tzba)3(H2O)6]·9DMF(compound 3).Novel secondary building blocks such as triangular[Ni3(μ3OH)(COO)3(tz)3(H2O)3],binuclear[M2(tz)3(H2O)3]and monometallic[M(COO)3]were observed for the first time.The diversity of coordination trends between Ni2+,Mn2+ and Zn2+ was found to be amplified during MOF self-assembly,leading to metal node evolution and subsequent large divergences in topological networks and framework dimensions.A series of experiments on three examples of high porosity MOF including bracketed solvent exchange,guest and temperaturedependent activation,N2 and CO2 gas adsorption,solution phase trapping of dyes and iodine,post-synthesis metal exchange and alkali-induced structural transformation of in situ amorphous electrocatalysts reveal dynamic MOF diverse stimulus-responsive structural modulation behaviour.In Chapter 3,the systematic preparation,active metal site construction and adsorption modulation of heterometabolic isomeric MOF were carried out using the linear[M3(COO)6(H2O)3]cluster-based MOF-[Ni3(bpt)2(DMF)2(H2O)2]·2DMF as the structural model.Six isomeric MOF(compounds 4-9)based on Co,Ni,Mn,Fe,Mg and Cu were successfully synthesized,and the framework stability and active metal site accessibility of these MOF were investigated by optimizing the low-boiling point solvent replacement,temperature and vacuum treatment time-dependent activation conditions.Based on systematic gas adsorption experiments,it was found that Ni metal-based MOF(compound 5)could be activated at 120℃ for 12 h after acetonitrile solvent replacement,and the specific surface area of the activated MOF reached 1572.7 m2/g and 412.5 cm3/g by 77 K nitrogen.The iodine adsorption was found to be 35%and 50%.In Chapter 4,two examples of high porosity carboxylic acid based dynamic MOF-[N(CH3)2]6[Zn16(btc)12(gac)(DMA)3(H2O)3]·17DMA(compound 10)and[(CH3)2NH2][Mn1.5(btb)(bdc)0.5]·4DMF·MeOH(compound 11)were subjected to structural dynamics,post-synthetic metal ion substitution and adsorption modulation studies.Both compounds are electronegative framework materials,which are difficult to activate effectively by conventional means such as solvent substitution and low-temperature vacuum treatment.The post-synthetic metal ion substitution behaviour of Cu,Cd,Fe,Mn,Co,Ni and Mg was investigated for the structural characteristics of compound 10,and it was found that the Cu2+ substitution behaviour in methanol solution effectively enhanced the framework stability of the compound.Compared with the adsorption amount of 4.5 cm3/g obtained after activation of the original synthetic MOF,the adsorption amount of the compound after Cu2+replacement,the specific surface area increased by about 360 m2/g.Further,iodine adsorption experiments in different phases and iodine capture studies at ultra-low concentrations were done for compounds 10 and 11,and it was found that the iodine adsorption in the liquid phase could reach 20-25%and the removal rate at ultra-low iodine concentrations could reach more than 90%. |
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