The Design And Preparation Of Zr-MOFs For Cephalosporins Adsorption In Water

Cephalosporin antibiotics have been commonly used for bacterial infections with the wide antibacterial spectrum and strong bacterial ability.However,because of the excessive use,cephalosporins have been detected in various aquatic environments,which unavoidably results in environmental and health concern.It is highly crucial to develop effective methods for cephalosporins removal from aquatic environment.Adsorption is a promising technology for its easy procedure,low consumption,little environmental risk and high efficiency.During the past decades,metal-organic frameworks（MOFs）,a kind of highly porous crystalline nanomaterials,have been an emerging focus in adsorption field,which attributes to the unique features such as the great specific surface area,high porosity and adjustable pore structure.In this work,based on the structure and properties of cephalosporins,the rational design of MOFs was achieved via metal doping,ligand adjustment and composite strategies for cephalosporins adsorption.The detail contents are described as following:（1）Bimetallic MOFs M-Ui O-66（M=Hf and Ti）were designed and prepared from Ui O-66via post-synthetic modification for the adsorption of cephalosporins.The structure,morphology,and stability of the as-prepared MOFs were fully characterized,and the adsorption performance was explored.Interestingly,as metals doping generated abundant defects to the structures,the adsorption performance was highly enhanced due to the increasing open metal sites,more positively charged surface and enlarged pore size.The experimental data was better fitted with pseudo-second-order model and Langmuir model,suggesting it was a monolayer chemisorption.Hf-Ui O-66 exhibited the best adsorption performance for cefoperazone,with the adsorption capacity of 346.0 mg g^-1and the removal rate of 92.5%.Hf-Ui O-66 remained the excellent adsorption performance when used in complex water samples.This research offered a prospective approach for cephalosporins removal,and expanded the application of designable high-performance MOFs by metal doping strategy.（2）A serious of analogue Zr-X-MOFs,Ui O-66,Ui O-67 and PCN-222,were prepared with Zr clusters,using 1,4-benzenedicarboxylate（BDC）,4,4’-biphenyldicarboxylate（BPDC）and tetrakis（4-carboxyphenyl）porphyrin（TCPP）as organic ligands,respectively.These three carboxylate ligands showed different lengths and chemical compositions,which generated MOFs with various pore size,surface area,aromaticity and stability,and finally influenced the adsorption performance for cephalosporins.The sequence for adsorption capacity was PCN-222>Ui O-66>Ui O-67.The adsorption data fitted pseudo-second-order and Langmuir models well,and the adsorption amount of PCN-222 was 2.3 times higher than that of Ui O-66.This work expounded the effect of ligands on MOFs structure and the adsorption performance for cephalosporins,which provided ideas for judicious ligand selection.（3）A novel MOF-chitosan-glyoxal（PCN@CSG）composite film was constructed by incorporating PCN-222 into chitosan（CS）substrate using glyoxal（GLY）as chemical cross-linker.The cross-linker improved the physical and mechanical properties of CS,making it suitable for aquatic application.The features of CS were extremely favorable for the adsorption of cephalosporins:the amino and hydroxyl function groups provided abundant active sites;the cationic character improved the electrostatic attraction towards negative species;the biodegradability was truly good for environmental protection.The adsorption of ceftizoxime on PCN@CSG film was described as a multilayer process mainly controlled by chemisorption.The adsorption capacity was561.7 mg g^-1 and equilibrium time was 60 min,which were better than most reported materials.More interestingly,the loading of PCN-222 into CS for shaping film made the handleability and recycling property even better.After five consecutive cycles,the removal rate was higher than90.0%,confirming the excellent reusability of PCN@CSG.In summary,this work achieved the effective removal of cephalosporins in water,and exhibited a great prospect of shaped MOFs-based adsorbents in adsorption field.