Construction Of Metal-organic Frameworks-based Environmental Functional Materials And Their Removal Efficiency And Mechanism Of Pollutants In Water

In view of the major strategic needs of the state to“resolutely fight the battle against pollution and promote the construction of ecological civilization to a new level”,there is an inordinate obligation to develop new principles and innovative technologies for effective removal of typical pollutants in water.New kinds of environmental functional materials play a crucial role in environmental pollution treatment.Thus,it is of significant research value to develop environmental functional materials with high activity,selectivity and stability to remove contaminants form water.Metal-organic frameworks（MOFs）are a novel class of inorganic/organic hybrid porous materials with large specific surface area,high porosity and adjustable compositions.which exhibits great application potential in the field of environmental remediation.How to construct novel MOFs based functional nanomaterials suitable for contaminants and application scenarios is an important current research topic.Based on this,typical inorganic pollutants（metalloid:antimony,oxyanions:phosphate ion）and electron-rich organic contaminants（bisphenol A）are selected as the research target.Based on the pollution characteristics and molecular structure features of these target contaminants,novelty MOFs based environmental functional materials are constructed by chemical regulation means（heterostructure and defect engineering）.Combining the theoretical calculation and experimental study to explore the internal working mechanism on the basis of elucidating the structure-activity relationship between the material microstructure and the performance.The main results can be summarized as follows:（1）Based on high toxicity and electroneutrality of Sb（III）,mainly in the form of Sb（OH）₃,a dual-functional Fe-based MOFs filter was designed.In which,ultra-fast conversion of high toxic Sb（III）to low toxic Sb（V）（Sb（OH）₆^-）was realized under the photoelectrochemical action,and synchronous removal of Sb（V）was realized by using the high affinity of Fe-O clusters to Sb species,thus,achieving“one-step”detoxification and sequestration of highly toxic Sb（III）.At 1.5 V and under illumination,a 97.7±1.5%Sb（III）transformation and a 92.9±2.3%Sb_total removal efficiency can be obtained using hybrid filter（CM（50:3））.Improved Sb（III）removal kinetics were observed when compared with conventional batch system（97.5%vs 75.8%）.A synergistic effect between photocatalytic（PC）and electrochemical（EC）process were identified.Electron paramagnetic resonance（EPR）and photochemical characterizations suggested that HO^·dominated the Sb（III）conversion.（2）Based on the structural characteristics of phosphate are tetrahedral.An advanced template-assisted strategy has been developed to fine-tune the phosphate adsorption performance of HP-MOFs by dictating the type of defects in HP-UiO-66（Zr）.To achieve this,monocarboxylic acids ligand of varying chain lengths have been employed as template molecules to fabricate an array of defect-rich HP-UiO-66（Zr）derivatives following removal of the template.The as-prepared HP-UiO-66（Zr）exhibits higher sorption capacity and faster sorption rate compared to the pristine UiO-66（Zr）.Particularly,the octanoic acid-modulated UiO-66（Zr）exhibits a high adsorption capacity of186.6 mg P/g and an intraparticle diffusion rate of 6.19 mg/g·min^0.5,which are 4.8 times and 1.9times higher than those of pristine UiO-66（Zr）,respectively.The results reveal that defect sites play a critical role in boosting the phosphate uptake performance,which is further confirmed by various advanced characterizations.Density functional theory（DFT）calculations reveal the important role of defects in not only providing additional sorption sites,but also reducing the sorption energy between HP-UiO-66（Zr）and phosphate.（3）Based on the feature of bisphenol A（BPA）molecular are electron-rich.A MOF-driven catalyst activated PMS system was constructed to selectively and efficiently remove BPA by using defective engineering to induct the production of singlet oxygen（¹O₂）.To achieve this,oxygen vacancy（Ov）in a host lattice was in situ generated and regulated by varying oxygen partial pressure during calcination of zeolitic imidazolate framework-67（ZIF-67）membranes.The as-prepared NFZ-5 membrane with the largest Ov content（δ,0.912）gave the highest ¹O₂ production（98.3%）and PMS activated BPA degradation kinetics(k=0.11 min^-1).Spectrometry characterization and DFT calculations have indicated the pivotal role of Ov in modifying surface chemistry of the catalytic membrane via enhancing the number of Lewis acid sites.These Lewis acid sites have facilitated the chemisorption of PMS onto membrane,and the resulting reactive intermediate complexes have altered the electron transfer direction between PMS and the catalyst.In summary,based on their physicochemical properties and structural characteristics of MOFs-based functional materials,this thesis explores the efficiency and mechanism of their efficient and stable removal of typical pollutants in water environment under different application scenarios.It provides a theoretical basis for the practical application of MOFs-based functional materials in the field of water environmental remediation.