Preparation Of Silver Supported By Functional Microporous Polymers And Performance Of Them For Catalytic Hydrogenation Of P-nitrophenol And Methyl Orange In Water

With the industrialization process and the rapid growth of the population,many highly toxic organic pollutants are discharged into the environment,which poses a great risk to the ecological environment and human health and safety.Among them,highly toxic organic pollutants discharged into the water environment are one of the more serious environmental threats due to their universality and mobility.Therefore,the development of safe and efficient catalytic materials to strengthen the treatment of water environmental pollution is of great significance to protecting the ecological environment and human life safety.The fine metal catalyst is a kind of highly efficient atomic material which can be used for catalytic degradation of highly toxic organic pollutants in water with high-density catalytic active sites.The catalytic activity of metal catalysts depends largely on the catalytic active atoms on the surface of the catalyst,so how to maximize the efficiency of metal atoms is particularly important for improving the catalytic activity of metal catalysts.As a result,researchers tend to synthesize metal catalysts with finer structures.conjugated microporous polymers（CMPs）can be flexibly adjusted and modified to change their morphology and chemical properties to meet special application requirements,and they have inherent microporous properties and through-holes provided by gelation.Provide transport channels and accessible catalytic active sites for the reactants.CMPs,as a support carrier,provide size limitation and anchoring site for highly dispersed metal nanoparticles（MNPs）,which is conducive to the separation and reuse of composite catalysts to avoid the loss of metal catalysts.In the meantime,the diversification and functionalization of the CMPs skeleton are conducive to enhancing the interaction with MNPs and prolonging the service life of catalysts.Therefore,CMPs may be a reasonable candidate for the fine synthesis of metal nanocatalysts.This work uses CMPs as a multifunctional support to support fine Ag metal catalyst to form a supported CMP-based catalyst and studies its application performance in the catalytic reduction of p-nitrophenol（p-NP）and/or methyl orange（MO）in water.The main research results of this paper are as follows:（1）In Chapter 2,CMP-bpy1 with bipyridine structure was successfully synthesized by Pd-catalyzed Sonogashira-Hagihara cross-coupling reaction between aryl alkyne and halide.The Brunauer-Emmett-Teller（BET）surface area of the physical adsorption isotherm diagram of the material was obtained by using BET theory,and the results showed that the specific surface area of CMP-bpy1 was 16.61 m²·g^-1.The average pore sizes of CMPs-bpy1 calculated by Barrett-Joyner-Hallender（BJH）method was 24.77 nanometers（nm）.The water contact angle experiment showed that the surface chemical oxidation modification reduced the water contact angle of CMP-bpy1 and increased its hydrophilicity to obtain the hydrophilic CMP-bpy1（HCMP-bpy1）.The Ag metal precursor was introduced into HCMP-bpy1 by solvent osmosis,and the Ag ion was reduced into fine Ag nanoparticles（Ag NPs）by Na BH₄ reduction to form a composite catalyst（Ag@HCMP-bpy1）with high catalytic activity.The Ag load of Ag@HCMP-bpy1 measured by inductively coupled plasma emission spectrometer was about 12.65 wt%.The reaction rate constant is often used to judge the performance of the catalyst.The rate constant k of Ag@HCMP-bpy1in the hydroreduction of p-NP was 0.01209 s^-1.（2）Given the poor catalytic stability of Ag@HCMP-bpy1 material,in Chapter 3,Ag@CMP-bpy2 was synthesized by optimized synthesis method.The chemical structure of the target material was analyzed by solid state NMR,Fourier transform infrared spectroscopy,Raman spectroscopy and powder X-ray electron diffraction.The BET surface area of CMP-bpy2 was 586.31 m²·g^-1.The average pore sizes of CMPs-bpy1 calculated by Barrett-Joyner-Hallender（BJH）method was 7.02 nm.Thermogravimetric analysis showed that CMP-bpy2retained more than 60%of its mass when the temperature increased to 300℃.The Ag metal precursors were introduced into CMP-bpy2 by solvent osmosis,and the Ag ions were reduced to fine Ag NPs by Na BH₄reduction/photoreduction to form Ag@CMP-bpy2.The chemical components and chemical states of the composites were analyzed by powder X-ray electron diffraction,energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy.Ag@CMP-bpy2 inherits the outstanding thermal stability of CMP-bpy2 matrix.Ag@CMP-bpy2 retains more than 80%of its mass when the temperature exceeds 500℃,and about 40%when the temperature reaches800℃.The Ag load of Ag@CMP-bpy2 measured by inductively coupled plasma emission spectrometer was about 2.98wt%.The particle size distribution of Ag NPs is affected by the concentration of metal precursors and the method of metal reduction.The average particle size of Ag NPs at Ag@CMP-bpy2-1 with 1mmol?L^-1 and Ag@CMP-bpy2-0.1 with 0.1 mmol?L^-1 were 7.16 nm and 1.92 nm,respectively.Compared with Ag@CMP-bpy2-1 obtained by Na BH₄ reduction,Ag@CMP-bpy2-1 obtained by photoreduction formed finer Ag NPs with narrower and more uniform particle size distribution.（3）To test the potential of synthetic materials in water treatment applications,in Chapter 4,the performance of Ag@CMP-bpy2 for catalytic hydrogenation of p-NP in wastewater was studied.The CMP network provides support and spatial restriction for the growth of Ag NPs,which helps to improve the stability of the composite catalyst.The synergistic effect between the two can promote the production of catalytic active molecules,which helps to improve the catalytic activity.Ag@CMP-bpy2 composites can effectively catalyze the hydrogenation of p-NP to p-aminophenol（p-AP）from wastewater.The rate constant k of Ag@CMP-bpy2 was 0.01238 s^-1.Ag@CMP-bpy2 also had stable catalytic performance and can be used for more than ten consecutive times.Meanwhile,Ag@CMP-bpy2 also showed outstanding catalytic performance in different water bodies.The rate constant k for Ag@CMP-bpy2 is0.01598 s^-1 and 0.01258 s^-1 for river and tap water samples containing p-NP,respectively.（4）To improve the processability and applicability of supported CMP-based catalysts and meet the requirements of complex external environment and diverse applications,in Chapter 5,the biphenyl-based CMP aerogel supported Ag material（Ag@CMPA-bph）with processability was synthesized,the properties of the material were systematically characterized,and the catalytic hydrogenation reduction performance of the material was tested.As well as,the performance of the material in the treatment of combined pollutant system containing p-NP&MO under continuous flow conditions was examined.Ag@CMPA-bph can be cut and compressed into a circular membrane material for use in continuous flow wastewater treatment units with a maximum permeability of 1600 L·m^-2·h^-1（LMH）.In the range of 1～50 rpm(1 rpm=2.5m L·min^-1),the catalytic reduction rates of p-NP or MO in the Ag@CMPA-bph membrane are close to 99.9%,and can run continuously for 4～10 min.The results of the continuous flow treatment of Ag@CMPA-bph membrane for the complex contaminated wastewater system show that,at 4 rpm,the reduction rates of Ag@CMPA-bph membrane for the treatment of the combined pollutant system containing p-NP&MO reach 98.7%（p-NP）and 97.7%（MO）,respectively.