Study On The Synthesis And Sensing Properties Of Metal-Organic Framework Films

After nearly 30 years of development,Metal-Organic Framework?MOF?materials have been a popular material in many applications,such as gas adsorption and separation,catalysis and sensing.Moreover,with the gradual and profound research of MOF,the research focus has been gradually shifted from the design and discovery of new structures to the development of high-performance and multifunctional materials and the preparation of their devices.Temperature plays an important role both in scientific and industrial field.Therefore,it is crucial to accurate measurement of temperatre.Traditional thermometers are all contact measurements with heat equilibrium between the sensor probe and tested samples during the test process.Therefore,these thermometers cannot apply to fast-moving or small-scale samples.To address these disadvantages,the luminescent MOF-based thermometers were developed.Therefore,the majority of studies in this thesis focus on the preparation of new luminescent MOF films and their appilations in temperature sensing.This thesis covers the following four parts:1)Three luminescent Ln-MOF films,Tb-BTC,Eu-BTC and Tb_0.55Eu_0.45-BTCfilms,were prepared via electrophoretic depositon on the unmodified substrate at room temperature.Moreover,the as-prepared Tb-BTC film was used for the detection of Cr³⁺ions in solution,as well as nitrobenzene,trinitrotoluene in gas phas.The resulting the film exhibited good sensing performance.In addition,the detection limitation of the film is 0.11 ppb,0.01 ppb and 0.53 ppm for Cr³⁺ions,nitrobenzene,and trinitrotoluene,respectively.2)The carbon quantum dots?C-QDs?functionalized metal-organic framework?MOF?composite film,a novel contactless solid optical thermometer,has been prepared via electrophoretic deposition?EPD?.The uncoordinated carboxylic groups can generate negative charges which facilitates the deposition of film on the positive electrode during the EPD process.Moreover,UiO-66-?COOH?₂ MOFs can absorb C-QDs from the solution and prevent C-QDs from aggregating,and the well-dispersed C-QDs impart fluorescence characteristics to composites.As-synthesized composite film was successfully used to detect temperature change in the range of 97-297 K with a relative sensitivity up to 1.3%K^-1 at 297 K.3)Two novel dual-emitting MOFs with intergrated lanthanide metals and luminescent ligand in a UiO-66-type structure,named Ln@UiO-66-Hybrid,were prepared via the combination of postsynthetic modification and postsynthetic exchange methods.Subsequently,the assynthesized MOFs were deposited onto fluorine tin oxide substrates through electrophoretic deposition by taking advantage of the charges from the unmodified carboxylic groups of the MOFs.The as-prepared Tb@UiO-66-Hybrid and Eu@UiO-66-Hybrid films were applied to detect temperature changes.The resulting Tb@UiO-66-Hybrid film exhibited good temperaturesensing properties with a relative sensitivity of up to 2.76%K^-1 in the temperature range of 303-353 K.In addition,the Eu@UiO-66-Hybrid film showed excellent temperature-sensing performance based on the energy transfer between the luminescent ligand?H₂NDC?and europium ions with a relative sensitivity of up to 4.26%K^-1 in the temperature range of 303-403 K.Moreover,the temperature meters can be reused without any performance loss.4)A novel dual-emitting metal-organic framework?MOF?based on Zr and Eu,UiO-66?Zr&Eu?,was built using a clever in situ postsynthetic exchange based strategy.With the assistance of polymers,the synthesized UiO-66?Zr&Eu?was subsequently deposited as thin films that can be utilized as smart thermometer.The UiO-66?Zr&Eu?polymer films exhibit good temperature sensing performance in the temperature range of 237-337 K.Moreover,the UiO-66?Zr&Eu?polymer films have a high sensitivity of up to 4.26%K^-1 at 337 K.Moreover,the temperature meters can be reused for 3 times without any performance loss.