Preparation And Electrochemical Application Of Metal Organic Frameworks Frameworks-based Composite Materials

Metal organic frameworks?MOFs?,as a new class of inorganic-organic hybrid crystalline materials with periodic network structure,are synthesized by coordination self-assembly metal ions or clusters of metal ions with organic ligands.Because of its unique physical and chemical properties,such as large specific surface area,high porosity,ordered porous structure and exposed active sites,MOFs has been widely used in the fields of catalysis,sensing,gas storage and separation.In addition,MOFs with redox activity can be synthesized by reasonably selecting metal ions and organic ligands with electrochemical activity.However,due to the poor conductivity and stability of most MOFs materials,their further application in the field of electrochemistry is limited.The introduction of new functional components into MOFs can not only improve the problem of poor conductivity and stability,but also give MOFs more abundant functional characteristics.Therefore,the design and synthesis of novel MOFs-based composite materials with specific functional characteristics can greatly promote the application of MOFs in electrochemistry.In this thesis,six kinds of MOFs-based composite materials modified electrodes were designed and fabricated based on the application of MOFs-based composite materials in electrochemical sensors and electrocatalytic hydrogen evolution.The performance of the modified electrode in electrochemical sensing/electrocatalytic hydrogen evolution was also studied.The specific research work is as follows:1.The Ce-MOF containing mixed valence state Ce³⁺/Ce⁴⁺was prepared by direct precipitation method and in situ partial oxidation method.The Cs/Ce-MOF composite was prepared by combining with chitosan with good biocompatibility and strong film-forming ability.The Cs/Ce-MOF composite modified electrode was constructed by drop coating method and used to study the electrocatalysis and sensing for tryptophan with the modified electrode.The study results show that the electrode has good sensing properties for tryptophan.The linear range for tryptophan detection is 0.25–331?M,the detection limit is 0.14?M.It has high selectivity,good anti-interference ability and the ability to detect in real samples.2.Pt@MIL-101?Cr?composites were prepared successfully using the classical MIL-101?Cr?metal-organic nanocage framework loaded with Pt nanoparticles.The Pt@MIL-101?Cr?composite modified electrode was constructed by drop coating method and used to study the electrocatalysis and sensing for xanthine with the composite modified electrode.The linear range for xanthine detection is 0.5–162?M,the detection limit is 0.42?M.It has high sensitivity,good anti-interference stability.The recovery detected in real samples ranged from 100.80%to 103.00%.3.Ag-MOFencapsulatedKegginPOMcrystallinematerials Ag₁₀?tta?₄?H₂O?₄(PW₁₂O₄₀)(abbreviatedasAgMOFPW₁₂)and Ag₁₀?tta?₄?H₂O?₄(SiW₁₂O₄₀)(abbreviated as AgMOFSiW₁₂)were synthesized by hydrothermal synthesis technique using Keggin type POMs(PW₁₂ and SiW₁₂),silver ions and organic ligand tetrazolium.AgMOFPW₁₂ was combined with conductive agent acetylene black?XC-72R?,and the AgMOFPW₁₂/XC-72R modified electrode was constructed by drop coating method and used to study the electrocatalysis and sensing for tryptophan with the composite modified electrodes.The results show that the electrode has good sensing properties for tryptophan.The linear range is 2.5–65?M,the detection limit is 1.66?M,and the sensitivity is 3.78?A·?M^-1·cm^-2.At the same time,the electrode also shows excellent performance in electrocatalytic hydrogen evolution.4.Cu-MOF encapsulated Dawson-type POMs crystalline materials Cu₆?pzta?₆?bpy?₃(P₂W₁₈O₆₂)(abbreviatedasCuMOFP₂W₁₈)and Cu₆?pzta?₆?bpy?₃(As₂W₁₈O₆₂)(abbreviated as CuMOFAs₂W₁₈)were synthesized by hydrothermal synthesis technique using Dawson-type POMs(P₂W₁₈ and As₂W₁₈),copper ions and organic ligands 4,4-bipyridine,5-?2-pyridyl?tetrazolium?5-?2-pyridyl?tetrazolium?.The CuMOFP₂W₁₈/XC-72R modified electrode was prepared by drop coating method and used to study the electrocatalysis and sensing for xanthine with the composite modified electrode.The sensor has a wide linear range of detection,low detection limit,high sensitivity,good stability,reproducibility and anti-interference ability.It was successfully employed to detect xanthine in real sample.It also shows excellent performance in electrocatalytic hydrogen evolution,and the Tafel slope is 51mV dec^-1.