Study Of Fabrication And Application Of Micro/nano Composite Structures Based On Metal-organic Frameworks

Recently,metal-organic frameworks（MOFs）have attracted many attentions due to their high specific surface area,regular pores,adjustable organic and inorganic compositions and various topological structures.With a variety of new MOFs emerging continuously,MOFs show great research value in many applications,such as gas storage and separation,catalysis,sensing and optoelectronics.However,the poor stability and week conductivity of MOFs due to their structures,limit their practical applications.Compared with single MOFs,it is widely considered as an effective way to prepare MOF composites with controllable active components and enhanced electrical properties and structural stability.Therefore,this paper studies the fabrication methods and applications of the micro/nano composite structures based on MOFs.The obtained new composite structures not only inherit the unique characteristics of MOFs such as multi-porosity and high specific surface area,but also effectively enhance the stability and electrical properties of the composites.At the same time,the regular pores of MOFs can be used as host of nanocrystalline,which expands the application field of MOF-based composites.The main research work of this paper is as follows:（1）An anisotropic epitaxial growth method of MOF-on-MOF core-shell nanostructure was proposed to prepare ZIF-67@ZIF-8 nanostructure.The formation and evolution mechanism of core-shell nanostructures was revealed,and the key influencing factors were identified.High PH value can promote the shedding of organic ligands to form high quality ZIF-8 structures.Besides,slow crystallization rate and similar core-shell cell parameters are conducive to the formation of uniform and topological core-shell structures.The obtained core-shell structures have been successfully applied to electrochemical sensors,with a high sensitivity of 0.607 m A cm^-2 mm^-1 for low concentration glucose solution（0.4-1.49 m M）.Due to the synergistic effect of the two MOFs,a great deal of highly active reaction sites were provided,which effectively improved the electrochemical sensitivity of the obtained composites,indicating the potential application value in electrochemical glucose sensors.（2）An method for the in-situ fabrication of self-supporting multistage nanocomposites based on MOF integration was proposed to prepare composite structures of ZIF-67/Cu（OH）₂ nanowires and ZIF-67/Cu-BTC polyhedron nanoflowers.By regulating the surface morphology of the micro-nano composite structures,the specific surface area can be effectively increased and the active sites can be enriched,which contributes to achieve the highly sensitive detection of glucose.High stability and high performance glucose sensor prototypes were prepared based on these two composite structures respectively.The electrochemical sensors based on ZIF-67/Cu（OH）₂ nanowires maintained 80%of the initial response after 30-day stability testing with the sensitivity of1.48 m A m M^-1 cm^-2（0.2-2 m M）and the response time of 8 s.The electrochemical sensor based on ZIF-67/Cu-BTC nanoflower demonstrated higher sensitivity(3.2 m A m M^-1 cm^-2)and faster response（5 s）,which could be attributed to its larger specific surface area and faster electron transfer rate,showing a broad application prospect in the field of electrochemical sensing.（3）A novel strategy based on in situ derivation of bimetallic MOF was proposed to prepare self-supporting ultrathin nanosheet arrays,C and N doped bimetallic oxides.It has been revealed that the fracture and recombination of coordination bonds were the main reasons for the formation of MOF derived structures.The derivatives not only inherit the unique properties of MOF structures,such as porous structures and large specific surface area,but also improve the electrochemical activity and electron transport rate with exposed metal oxide nanocrystals（10 nm）,which leads to more active sites.The obtained structures have been successfully applied to the electrochemical glucose sensor,with high sensitivity(18.68 m A mm^-1 cm^-2)and rapid response（1.5 s）,making it an ideal structure for high sensitivity and rapid detection of the electrochemical glucose sensor.At the same time,this work provides a general method for in-situ integration of other polymetallic MOF derivatives,which possesses great application research value.（4）A method for confined growth of nanocrystals based on MOFs was proposed.The mechanism of phase transformation and nucleation of perovskite nanocrystals triggered by polar solvents at the interface was revealed.The obtained Cs Pb X₃@ZIF-8 composite structures with controllable emission wavelength show excellent photoelectric properties and significantly enhanced structural stability,and have been successfully applied to white light-emitting diodes（WLEDs）with wide color gamut,showing a broad application prospect in the lighting field.This work also provides a new approach for the integration of MOF with nanocrystalline systems,and expands the functional applications of MOF structures.