Preparation Of Functionalized Covalent Organic Frameworks And Study On Adsorption Of Heavy Metals And Photocatalytic Detoxification Of Sulfur Mustard Simulant

Porous Organic Materials（POMs）are a class of macromolecular materials constructed from organic units with light elements such as C,N,O and S.These materials have attracted much attention for their excellent stability,pre-designability,large specific surface area,porosity,catalytic properties,and versatility in synthesis.These materials have attracted a lot of attention for their excellent stability,pre-designability,large specific surface area,porosity,catalytic properties and diversity of synthesis methods,therefore play important roles in the fields of catalysis,adsorption,fluorescence and storage of gases.In recent years,more and more porous organic materials are making great contributions in the two major fields of adsorption of metals and photocatalysis,providing a faster,more economical and more efficient idea for environmental problems of wastewater treatment and making full use of renewable energy-light energy.Heavy metals in wastewater,such as palladium and gold,flow into the natural environment and pose a great threat to human health through accumulation in the food chain.In addition,heavy metals are highly soluble and non-degradable in the aqueous environment,making them more persistent than organic pollutants.Therefore,the design and synthesis of porous organic materials with specific binding sites for heavy metals is expected to solve this thorny problem.In addition,porous organic materials with photocatalytic properties can achieve in situ photocatalytic reduction of heavy metal ions to insoluble materisls after their preenrichment,such as Pd⁰ and Au⁰,thereby regenerating the adsorption sites for the purpose of increasing the adsorption capacity.In addition,porous organic materials are emerging in the adsorption and photocatalytic detoxification of the chemical warfare agent bis（2-chloroethyl）sulfide sulfide.In this thesis,porous organic materials were designed and synthesized and used to study the adsorption performance of palladium and gold,and the photocatalytic reduction of heavy metals and detoxification of chemical warfare agents by porous organic materials were investigated.The main research contents are as follows.1.Three cationic covalent organic frameworks DHBD-TGC,HBD-TGC and BD-TGC were synthesized from triaminoguanidine chloride（TGC）and aldehyde monomers2,5-dihydroxy-1,4-benzenedicarboxaldehyde（DHDB）,2-hydroxy-1,4-benzenedicarboxaldehyde（HDB）and 1,4-benzenedicarboxaldehyde（DB）by Schiff base reaction for rapid and selective recovery of gold.The cationic covalent organic frameworks（i COFs）contain charged organic units with extraordinary electrostatic properties and exhibit relatively high removal efficiency for Au Cl₄^-in aqueous environment.Since most metal ions exist as cations in aqueous bodies,while gold exists as the anion Au Cl₄^-,this peculiarity allows the cationic covalent organic frameworks DHBD-TGC,HBD-TGC and BD-TGC to selectively adsorb Au Cl₄^-in mixed metal ion solutions.It was shown by XPS analysis that Au Cl₄^-was reduced to Au⁰ thus regenerating the adsorption sites and increasing the adsorption capacity.This is mainly due to the reduction of hydroxyl groups,reducing Au Cl₄^-to Au⁰,so the DHBD-TGC with the most hydroxyl content with an ultra-high adsorption capacity for Au Cl₄^-.This strategy provides a new idea to expand the application of cationic covalent organic framework and to efficiently recover anionic metal complexes in aqueous environment.2.Molecularly imprinted triazine-based porous aromatic frameworks（MI-TBPAFs）were constructed using molecular imprinting technology（MIT）for selective extraction of palladium and in situ photocatalytic reduction.The Pd-vinylpyridine complex（Pd@Vpy）was first synthesized,and then a series of MI-TBPAFs were constructed by Heck-couple reaction with tris（4-bromophenyl）-1,3,5-triazine（TBT）and Pd@Vpy.After removing the template Pd²⁺,there were many customized binding sites in MI-TBPAFs that could be used for selective complexation of Pd²⁺in aqueous solution,thus MI-TBPAFs exhibit a remarkable selective affinity for Pd²⁺.Notably,MI-TBPAF-3 exhibited an ultra-high adsorption capacity for Pd²⁺under simulated sunlight radiation,which was much higher than that under dark conditions.The photoelectric properties study showed that the extendedπ-conjugated framework with triazine units of MI-TBPAFs endowed the material with the advantages ofπ-electron leaving domains and low optical band gap for the photocatalytic reduction of Pd²⁺.Meanwhile,the mechanistic analysis showed that the nitrogen atom of the pyridine ring in MI-TBPAFs acts as a chemically active site for the redox reaction.MI-TBPAFs organically combined the advantages of three synergistic mechanisms,namely MIT,photocatalytic reduction and chemical reduction,which not only provides a new strategy for the efficient extraction of Pd,but also provides a new idea for the recovery of precious metals.3.Sp²-C conjugation metal-covalent organic frameworks（MCOFs）were synthesized for photocatalytic detoxification of 2-Chloroethylethyl sulfide（CEES）,an analogue of Sulfur mustard（bis（2-chloroethyl）sulfide,HD）,and oxidation of CEES to less toxic CEESO（2-Chloroethylethyl sulfoxide）,thus achieving the detoxification of highly toxic chemical warfare agents to less toxic chemicals.Cu-TMT was synthesized by means of a structure containing within Cu₃（Py CA）₃·H₂O single crystal containing three copper metal sites and2,4,6-trimethyl-1,3,5-triazine（TMT）undergoes hydroxyl aldol condensation to construct the unsubstituted olefin（-CH=CH-）linkage to form the sp²-C metal covalent organic framework,Cu-TMT.Due to the large number of metal sites within the framework,Cu-TMT with remarkable photophysical properties to rapidly produced large amounts of ¹O₂ for the oxidation of CEES.Degradation experiments showed that Cu-TMT achieved the oxidation of CEES to CEESO within five minutes under light conditions,and its efficient degradation rate was comparable to that of the already reported materials.In addition,the Cu-TMT framework was highly stable and remains chemically stable in extremely harsh environments because it consists of a stable-C=C-succession.The novel sp²-C MCOFs are proposed to provide a new idea for the degradation of toxic organic compounds.