Preparation Of Porous Aromatic Frameworks By Lewis Acid Catalysis In Combination With Mechanical Chemistry

Porous organic frameworks(POFs)are a new type of porous materials,which are formed by the polymerization of organic building blocks through covalent bond.The structure and composition of POFs determine that they have many advantages,such as high stability,design structure,easy functionalization and high specific surface area,etc.POFs have good promising applications in gas adsorption and separation,energy storage and conversion,photoelectricity and catalysis.Currently,dozens of polymerization reactions have been reported for the synthesis of POFs(a)some polymerization reactions require the use of expensive catalysts,the reaction systems isharsh(oxygen and water sensitive),the production cost is high,the production process is cumbersomes,and it difficult to carry out mass production;(b)most POFs are carried out in systems of organic solvents,the use of solvents increases the processing process and the risk to human health and the environment of excessive use;(c)some polymerization reactions require the use of special organic building blocks,which are difficult to synthesize and costly,and they are not conducive to mass production.If POFs can be applied,on the one hand,costs need to be controlled(including catalysts,organic monomers and solvents);on the other hand,the synthesis process is simple.Therefore,this thesis is devoted to explore the use of relatively cheap lewis acid catalysts(Fe Cl₃)and organic substrates,the use of mechanical ball mill to prepare PAFs,and the adsorption and separation properties of small hydrocarbons are studied.The details are as follows:1.Mechanical ball milling drives the direct coupling of benzene rings to prepare PAFs and its adsorption properties for low-carbon hydrocarbons.The cheap p-triphenyl,o-triphenyl,triphenylamine and biphenyl are employed as monomers,and Fe Cl₃ as catalyst,to adjust the ratio of monomer to Fe Cl₃,PAF-104s,PAF-105s,PAF-106s and PAF-107s are prepared by mechanical ball milling.The infrared spectra and solid state NMR prove that the monomer polymerization have occurred.microsope images show that these PAFs are not regular.Nitrogen adsorption-desorption results show that the BET surface areas of PAFs synthesized by by p-triphenyl,o-triphenyl and biphenyl are not high(less than 160 m² g^-1),and the PAF prepared by triphenylamine has higher surface area.When triphenylamine:Fe Cl₃=1:12,the surface area of PAF-106c reaches 280 m² g^-1,which is highest among these PAF materials.At 273 K and 298 K,the C2 hydrocarbon adsorption and separation property of PAF-106c are studied.At 273 K and 1 bar,the adsorption uptake of C₂H₂,C₂H₄ and C₂H₆ for PAF-106c is 11.5 cm³ g^-1,10.1 cm³ g^-1,and 10.9cm³ g^-1,respectively.At 298 K and 1 bar,the adsorption uptake of C₂H₂,C₂H₄ and C₂H₆ for PAF-106c is 10.3 cm³ g^-1,6.8 cm³ g^-1 and 8.8 cm³ g^-1,respectively.2.PAFs with methylene bonded phenyl skeletons prepared by mechanical ball milling and its low carbon hydrocarbon adsorption properties.The p-triphenyl,o-triphenyl,triphenylamine and biphenyl are employed as monomers,Fe Cl₃ as catalyst,and dimethyl alcohol formaldehyde(FDA)as crosslinking agent,to adjust.the ratio of monomer,Fe Cl₃,and FDA,several PAFs(PAF-104s,PAF-105s,PAF-106s and PAF-107s)are prepared by mechanical ball milling.Infrared spectroscopy,elemental analysis,X-ray photoelectron spectroscopy and solid state nuclear magnetic field(NMR)prove that the polymerization has taken place.The ratio of monomer,Fe Cl₃ and FDA will affect the porous property of these PAFs.p-triphenyl:Fe Cl₃:FDA=1:9:9,the BET surface area of PAF-104f is 840 m² g^-1;o-triphenyl:Fe Cl₃:FDA=1:12:12,the BET surface area of PAF-105g is 684 m² g^-1;triphenylamine:Fe Cl₃:FDA=1:3:3,the BET surface area of PAF-106d is 132 m² g^-1;biphenyl:Fe Cl₃:FDA=1:3:3,the BET specific surface area of PAF-107c is 470 m² g^-1.In addition,the adsorption and separation properties of small hydrocarbons(C1,C2 and C3)are investigated at 273 K and 298 K.Among them,the adsorption uptake of C₂H₄,C₂H₆,and C₂H₂ for PAF-104f is the highest.At 273 K and 1 bar,the uptake of C₂H₄,C₂H₆ and C₂H₂ for PAF-104f is 50.5 cm³ g^-1,54.3 cm³ g^-1 and 71.8 cm³ g^-1respectively.At 298 K and 1 bar,the uptake of C₂H₄,C₂H₆and C₂H₂ for PAF-104f is44 cm³ g^-1,45.6 cm³ g^-1 and 55.9 cm³ g^-1,respectively.At 273 K and 1 bar,the uptake of CH₄,C₂H₆ and C₃H₈ for PAF-107c is 16.3 cm³ g^-1,48.5 cm³ g^-1 and 70.5 cm³ g^-1,respectively.At 298 K and 1 bar,the uptake of CH₄,C₂H₆ and C₃H₈ for PAF-107c is8.7 cm³ g^-1,32.5 cm³ g^-1 and 49.5 cm³ g^-1,respectively.The separation selectivity of C₃H₈/CH₄,C₂H₆/CH₄ and C₃H₈/C₂H₆ for PAF-107c is 27,9,and 5 at 273 K and 100k Pa,respectively,which is calculated by IAST(ideal adsorption solution theory).