The Investigation On The Synthesis Of Porous Aromatic Frameworks Under Atmospheric Environment

Porous aromatic frameworks（PAFs）are a new type of polymeric reticular materials with persistent micropores.The structural feature of PAFs contains the aromatic-based building units and the connection through covalent C-C bonds.PAFs possess open framework and can be used as host materials for small molecules.The synthesis of porous aromatic frameworks usually depends on the formation of coupling reactions,including Friedel-Crafts alkylation reaction,Scholl reaction,Sonogashira-Hagihara cross coupling reaction,nickel（0）catalyzed Yamamoto type Ullmann coupling reaction,etc.Due to their high structural stability,large specific surface area,diverse pore volume,and feasible functional modifiability,PAFs have exhibited a wide range of applications in membrane separation,catalysis,gas adsorption,sensing and other fields.However,PAFs synthesized by solvothermal method usually require a large amount of organic solvents,which are harmful to human body and environment,and the production,purification and recovery of solvents require high costs.In addition,many PAFs are synthesized by coupling reactions catalyzed by organometallic compounds.These catalysts are generally sensitive to air,therefore the reaction process needs to maintain strict anhydrous and oxygen-free conditions.The harsh operation requirements hinder the scale up process of PAF synthesis.Therefore,we focus to explore the synthesis of PAFs in the air environment through green chemistry route.Compared with traditional synthetic methods,mechanochemistry relying on mechanical force can effectively avoid the use of a large number of harmful solvents,with low energy consumption and simple operation steps.It is a synthetic method in line with the principle of"green chemistry".In recent years,with the increasing attention paid to environmental protection,mechanochemistry has once again attracted the attention of scientists.In chapter 2,we solved the problem of using large amount of solvent by mechanochemical method in the air environment,and synthesized three kinds of PAFs based on Friedel-Crafts alkylation reaction and Scholl reaction using ball milling technology,namely PAF-32-M,PAF-56-M and PAF-45-M.Ball-milling synthesis only needs 1.5 m L of auxiliary solvent to replace the amount of solvent used in the traditional solvothermal method to synthesize PAFs.The specific surface areas of the synthesized PAFs are as high as 950 m²·g^-1,473 m²·g^-1 and 544m²·g^-1.Compared with PAFs synthesized by traditional solvent method,their specific surface area is comparable or even higher.Aromatic aminodiazotization reaction is a convenient and efficient reaction with a wide range of applications,and the resulted diazonium salt can be used as a reaction monomer to prepare various organic compounds and participate in a variety of reaction types.In Chapter 3,under the principle of topology design,tetrakis（4-diazophenyl）methane was synthesized from tetrakis（4-aminophenyl）methane,and was used for the synthesis of PAF-141 under the catalysis of palladium acetate.This synthesis process can be simply operated in air environment.It has provided a new approach for the synthesis of porous aromatic frameworks in an open environment.