Preparation Of Ionic Covalent Organic Framework Materials And Their Adsorption Properties And Mechanism For Diclofenca And Ketoprofen

In recent years,the overuse of non-steroidal anti-inflammatory drugs（NSAIDs）has adversely affected human health,water quality,and the entire ecosystem.Currently,various techniques have been widely used to remove NSAIDs,but traditional wastewater treatment methods cannot completely remove NSAIDs.The significant attribute of NSAIDs is that their own molecular structure has different functional groups,which can provide ideal ion binding sites.Adsorption technology has become a promising technology for the removal of NSAIDs because of its simple operation,reusability,and ability to reduce secondary pollution.Traditional adsorbents have some disadvantages such as irregular pores and uneven distribution of functional sites.The orientable design and flexible tunability of ionic covalent organic frameworks endow covalent organic frameworks with the advantage of producing strong attractive interactions with oppositely charged ionic species.This overcomes the shortcomings of traditional adsorbents.In this study,two kinds of ionic covalent organic frameworks（i COFs）with different pore sizes were synthesized by a simple solvothermal method by reacting dialdehydes with different chain lengths with triaminoguanidine salts through Schiff base reactions[TPA-TG_Cl and BPDA-TG_Cl].The i COFs were characterized by various techniques,and the adsorption behavior of diclofenac and ketoprofen on i COFs was explored in detail.The specific content and results are summarized as follows:（1）The adsorption isotherm experiments showed that the adsorption capacity of TPA-TG_Cl to DCF and KT was higher than that of BPDA-TG_Cl.All experimental data of adsorption isotherms showed the highest correlation with the Langmuir model（R~2>0.99）.Among them,the maximum adsorption capacities of TPA-TG_Cl for DCF and KT were 724.64 mg·g^-1 and240.96 mg·g^-1,respectively.The maximum adsorption capacity of DCF on TPA-TG_Cl was 9times that of commercial activated carbon,27 times higher than that of carbon nanospheres,almost triple that of a magnetic cellulose ionomer/LDH,and two-fold higher than that of Ui O-66-SO₃H.（2）The adsorption kinetics experiments showed that the adsorption equilibrium of TPA-TG_Cl occurred earlier than that of BPDA-TG_Cl.The second order kinetic model rate constant of TPA-TG_Cl(2.14×10^-4 g·mg^-1·min^-1)was higher than BPDA-TG_Cl(1.58×10^-4 g·mg^-1·min^-1).All the experimental data of adsorption kinetics had the highest correlation coefficient（R~2>0.99）with the pseudo-second-order kinetic model.（3）The high density and uniform distribution of guanidine-based monomers within i COFs triggering electrostatic interactions and theπ-πstacking interactions between covalent organic frameworks and pollutants are the main intrinsic driving forces for the efficient removal of DCF and KT.（4）In addition,TPA-TG_Cleffectively achieved five adsorption-desorption cycles and the adsorption capacity was basically the same.TPA-TG_Clstill maintained a good structure after five cycles of regeneration.These results demonstrate that i COFs are efficient and recyclable adsorbents with potential applications in water environment remediation,and also provide a scientific basis for the design of functional materials.