Controllable Preparation And Selective Adsorption Property Of Water-Stability MOF Materials

With the rapid development of industrialization since the outbreak of the second Industrial Revolution,a series of environmental problems have appeared,among which the water pollution caused by waste metal ions discharged by various factories has aroused people’s concern.Adsorption separation technology has become the most common strategy to solve metal ion pollution due to its simplicity,convenience,flexibility,easy regeneration.However,the characteristics of low reuse rate,poor selectivity and low adsorption capacity limit the application of traditional adsorbent such as activated carbon.Therefore,scientists turned their attention to the preparation and application of other porous materials.Among many porous materials,metal-organic framework materials（MOF）stand out due to their high specific surface area,porosity,flexibility of pore size adjustment and diversity of active sites.At present,the research on the application of MOF in the treatment of metal ion pollution is not comprehensive,especially when MOF is applied to the treatment of metal ion pollution.Many MOF adsorbents with poor water stability cannot be reused for multiple times,which will cause corresponding secondary pollution.On the other hand,how to maintain the relatively complete pore structure and unobstructed ion transport channel of MOF to the maximum extent and make the functional groups evenly distributed in the ion transport channel also needs to be further explored.In addition,many scientists mostly pay attention to the adsorption of metal ions by MOF,but little attention is paid to the separation of metal ions by MOF（selective adsorption of specific metal ions）.Therefore,MOF-801and MOF-303,two MOF materials with water stability,were prepared by hydrothermal method,and their potential in selective adsorption of metal ions was studied.The specific research contents are as follows.1.MOF-801 and MOF-303,two MOF materials with water stability,were prepared by hydrothermal method and systematically characterized respectively.MOF-303 and MOF-801 with specific surface area of 1048 m²·g^-1and 370 m²·g^-1were obtained.2.The adsorption performance of MOF-801,MOF-303 and other traditional materials for Fe³⁺,Cr³⁺and other metal ions was compared,and MOF-303 was confirmed to have excellent selective adsorption performance.The adsorption behavior and influencing factors of MOF-303 for Fe³⁺/Cr³⁺system was systematically studied.The results are as follows:In the p H range of 0-3,the adsorption capacity and separation performance are positively correlated with Ph;Temperature（T）has almost no effect on the adsorption of Fe³⁺,but promotes the adsorption of Cr³⁺;The adsorption behavior of MOF-303 for Cr³⁺fits the pseudo-first-order kinetic model,and that of Fe³⁺fits the pseudo-second-order kinetic model.The results on recycling of adsorbent show that MOF-303 material has good regeneration ability.3.The mechanism of MOF-303’s selective adsorption on Fe³⁺/Cr³⁺system was investigated.The driving force of MOF-303’s selective adsorption on Fe³⁺/Cr³⁺system was found to be the strong coordination interaction between organic ligand N site and Fe³⁺.