| As an energy-saving and eco-friendly method,adsorption separation has become an important technology in industrial production.It has been widely used in sewage treatment,desalination,biomedicine,fine chemical industry,and other fields.The core of adsorption and separation technology is to develop efficient adsorption and separation materials.Metal-organic framework(MOF)has great potential in the field of adsorption and separation because of its unique porosity,chemical versatility,and structural designability.MOF membrane has also been widely used in liquid phase separation.However,different liquid phase separation systems also put forward different requirements for the function of MOF membrane.Therefore,exploring and summarizing the requirements of different separation systems for MOF membrane,and designing MOF or MOF-based composite materials according to these requirements is of great significance to expanding the application of MOF membrane.Based on the properties of guest molecular and the requirements of the separation system for MOF,this study adopted the method of combining theory and experiment to construct MOF membrane for different adsorption separation systems.Through the reasonable design of MOF and the preparation method of MOF membrane,we obtained MOF membrane with excellent adsorption and separation performance.The main contents of this thesis were listed as follows.(1)It is of great significance to expand the application of MOF in different liquid phase adsorption and separation.Taking the advantage of the structural diversity and modifiability of MOF,we designed MOF for different adsorption separation systems.(ⅰ)UiO-66-SO3H and UiO-66-(COOH)2 were obtained by modifying UiO-66 with functional groups(sulfonic acid group and carboxyl group).The adsorption properties of UiO-66,UiO-66-SO3H,and UiO-66-(COOH)2 for uremic toxins were investigated.The effect of the functional group on the adsorption performance of UiO-66 was studied.The experimental results showed that UiO-66-SO3H and UiO-66-(COOH)2 have better adsorption properties.The adsorption mechanism of three kinds of Zr-MOF was studied by DFT calculation.It was found that the modification of functional groups strengthened the role of hydrogen bonds and Coulomb interaction in the adsorption process.(ⅱ)L-histidine@ZIF-8(His@ZIF-8)was synthesized by the mixed-linker synthesis method.The effects of His content on the physical and chemical properties of His@ZIF8 were studied.Compared with ZIF-8,His@ZIF-8 showed more excellent wettability and adsorption ability for heavy metal ions.The adsorption mechanism of His@ZIF-8 for heavy metal ions was analyzed by XPS,FT-IR,and SEM.(ⅲ)UiO-66-(OH)2@Fe2O3 were synthesized by a "phenol-Fe" reaction and used for the adsorption of phosphate.Fe2O3 can improve the adsorption performance for phosphate by synergistic adsorption and improving the surface charge of UiO-66-(OH)2.The experiment showed that the adsorption of phosphate by UiO-66-(OH)2@Fe2O3 is mainly through surface complexation and ligand exchange.(2)Due to the unique pore structure,MOF can prevent the adsorption of protein and other macromolecules,and adsorb small uremic toxins.Therefore,it is of great significance to study the application of MOF in hemoperfusion or hemodialysis.In the second work,three kinds of Zr-MOF-based mixed matrix membranes(MMMs)were prepared by the blending method,and the potential of MOF-based MMMs in hemodialysis was explored.The MMMs showed a high water flux up to～260 L·m-2·h-1,which was much higher than that of the PLA membrane(～125 L·m-2·h-1).Under static conditions,the MMMs could remove HA and IS with a percentage of 75%and 78%in 4 h,respectively.Under dynamic conditions,MMMs could remove 57%of IS and 54%of HA in 30 min,respectively.In addition,the MMMs prepared by this method also have good blood compatibility and biocompatibility.(3)The separation performance of a ZIF-8-containing membrane is limited by the poor surface and molecular sieving properties of ZIF-8.In the third work,a continuous mixed-linker L-histidine@ZIF-8(His@ZIF-8)layer was synthesized on the amyloid nano fibrils(ANFs)-modified hydrolyzed polyacrylonitrile(HPAN)membrane through a combination of self-assembly and in situ growth methods.The mixed-linker approach facilitated the tuning of surface and molecular sieving properties of ZIF-8 on the membranes,which effectively improved the overall separation and antifouling performance of the His@ZIF-8/ANFs membrane.Compared with the ZIF-8/ANFs membrane,the resultant His@ZIF-8/ANFs membrane exhibits higher water flux(42.6 vs 27.9 L/m2·h·bar)and outstanding heavy metal ion(Cu2+,Ni2+,Pb2+,and Cd2+)rejection(>98.6%vs 91.2%).Moreover,the His@ZIF-8/ANF membrane also exhibited excellent integrated biological and organic antifouling performances.The antibacterial efficiency of the membrane against Escherichia coli was as high as 82.9%,which is much higher than ANFs/HPAN membrane(16.7%).Therefore,through the mixed-linker approach,the separation and antifouling performance of the ZIF-8 membrane was improved by mixed ligand synthesis.(4)Zirconium-based materials have adsorption selectivity for phosphate,and Zr-MOF was also used as an adsorbent for phosphate.However,there are often a large number of microorganisms in phosphorus-rich water.Therefore,the antifouling performance needs to be considered for designing adsorbents for the removal of phosphate.In the fourth work,we fabricate a MOF-supported carbon fibers(CFs)membrane,namely UiO-66-(OH)2@Fe2O3@CFs,which uses CFs as a scaffold and in-situ synthesis of well-dispersed MOF derivative as adsorbent and photocatalyst.The UiO-66-(OH)2@Fe2O3/CFs membrane exhibits a maximum phosphate adsorption capacity of 333.3 mg/g through the strong chemical bond.Specifically,the photocatalysts Fe2O3 nanoparticles anchored on the surface of UiO-66-(OH)2 through’phenol-Fe(Ⅲ)’ rection endow the membrane with excellent adsorption recovery via the robust photo-Fenton catalytic activity,which improves long-term reusability even under algae-rich condition.Moreover,the growth of algae C.pyrenoidosa was significantly reduced via metabolism inhibition due to membrane-induced P-deficient conditions.Hence,the developed UiO-66-(OH)2@Fe2O3/CFs membrane holds significant prospects for large-scale application in phosphate sequestration of eutrophic water bodies. |
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