Metal-organic Frameworks Constructed From A Tetrahedral Silicon-based Linker For Selective Adsorption Of Methylene Blue

With the development of the dyes industry in our country,dye production increased year by year.Dye wastewater quantity increased year by year,it gives human hurt even carcinogenic,it is necessary to solve dye waste water treatment problem.Therefore,to explore effective dyes wastewater treatment method has very important significance.Adsorption method is an efficient and economic method of treatment in dye wastewater treatment,which has received the widespread attention.And adsorbent adsorption process is to determine efficient performance of the key factors,activated carbon is applied as adsorbent in industry,but its price is more expensive,regeneration rate is low,so,we are looking for a cheap adsorbent material to reduce the cost of the dye wastewater treatment,and improve the efficiency of purification,it has become a problem to be solved in the environmental protection.As a new type adsorption material of MOFs,not only it can adsorption of dye molecules,but also it can achieve the selective adsorption of dye molecules.MOFs materials as adsorbent is characterized by specific large surface area? open pore structure and chemical regulatory,therefore MOFs is used as adsorbent to treat dye wastewater,it is a kind of potential applied material.Under the solvothermal conditon,a tetrahedral silicon-centred linker with space-directed has been employed to successfully construct three novel adsorbents with diverse networks,namely,[Cd2?H2O?2L]·5H2O·0.5DMF?adsorbent 1?,[Co3O?H2O?3L?ttb?]·3H2O?adsorbent 2?,[Zn3O?H2O?2L?ttb??DMF?2]·2H2O?adsorbent 3?,respectively.They have been structurally confirmed by single-crystal X-ray diffraction and further characterized by elemental analysis and thermogravimetric analysis?TGA?.N₂ adsorption experiment proves that all three adsorbents are three dimensional structures with high porosity.The absorption of dye solution on our adsorbents are conducted by UV-visible spectrophotometer Adsorbent 1 shows a rapid selective absorption ability of methylene blue,with maximum adsorption of 1008.9 mg g-1.?1?Single-crystal diffraction analysis reveals that adsorbent 1 crystallizes in the monoclinic space group C2/c adsorbent 2 in the P21/c space group,adsorbent 3 in P21/n space group,respectively.What's more,adsorbent 3 displays a two-fold interpenetrating three-dimensional structure.?2?The powder X-ray diffractions of as-prepared adsorbents were recorded and compared with their corresponding simulation patterns.The results show that the experimental patterns match very well with the simulation patterns with slightly difference in intensity which is the result of the preferred orientation of crystals.?3?The N₂ adsorption curves suggest that adsorbent 1 and 3 exhibiting relatively larger specific surface area than adsorbent 2.?4?The absorption of dye solution on our adsorbents are conducted by UV-visible spectrophotometer,and the results show that adsorbent 1 shoes the very good adsorption effect on methylene blue?MB?,absorption capacity reached 1222.5 mg g-1,what's more,adsorbent 1 displays the ability of selective adsorption of methylene blue in the mixed aqueous solutions of both methylene blue and some other dyes..?5?According to the methylene blue?MB?absorption curve,two step adsorption process exists,firstly,methylene blue?MB?dye molecules was absorbed into the channel along the C axis of the adsorbent 1;Secondly,considering adsorbent 1 and dye molecules have benzene ring species,the ?-? and p-? interations occur between adsorbent 1 skeleton structure and object of dye molecules.?6?The impact of other factors on the adsorption performance,we study the effect of pH on the adsorption performance,salt effect on the properties of adsorption,the influence of organic matter on adsorption performance.