| In recent years,the concentration of carbon dioxide(CO2)in the atmosphere has been rising,and the subsequent global warming has led to a series of natural disasters,such as melting glaciers,extreme weather and rising sea levels,destroying the ecological balance and creating a huge economic loss for human.Energy conservation and emission reduction increasingly aroused people's concern.Clean and efficient natural gas has become the primary choice to adjust the energy structure.Removing CO2 from natural gas can improve energy density and reduce equipment corrosion.Natural gas decarburization technology has become a hot topic to researchers,in which the adsorption storage with nano-porous material is considered as one of the effective ways for carbon capture.CO2 molecules own dipole moment and CH4 is a non-polar molecule,so increasing the polar functional groups on the pore wall surface can improve the CO2 adsorption and CO2/CH4 selectivity.Metal-organic frameworks(MOFs)materials owns the exposed metal sites with D orbit,and the strong polarity can enhance the electric field on hole wall which can improve the C02 adsorption capcity.But the poor hydrothermal stability of the material limits its application.Covalent Organic Polymers(COPs)are new kinds of porous organic materials linked by covalent bonds.They have large specific surface area and pore volume,rigid skeleton structure and very good hydrothermal stability.Its pore structure and surface functional groups can be precisely regulated and modified.Researchers have done lots of exploration in the gas storage,fluorescence,drug transport,catalysis and so on.Metal-doped into COPs can both ensure the stability of the material and improve the carbon capture preformance.However,the current coverage about this area is relatively less.In this paper,two kinds of COPs were prepared with different ligand molecules by Yamomato-type Ullmann coupling reaction.The doping of non-noble metal elements was carried out in the early and later stage,respacrely.These materials could be applied in the decarburization of natural gas.The main contents and innovations of this paper are as follows:1.The metal ions were bonded to the monomer 5,10,15,20-Tetrakis(4'-bromobiphenyl)porphine(TBBPP)in the form of a coordination bond.The covalent organic polymeric materials were synthesized with metal-doping monomer.After carbonization,we obtained porous graphite carbon material doped with non-noble metal,iron(Fe),cobalt(Co)and Manganese(Mn).ICP-AES showed that the contents of metals in the three samples were about 10%,and the content of manganese in C-COP-P-Mn reached 11.35%.HTEM,PXRD and XPS show these metal components belong to the typical Mn7C3(01 3;ICSD75-1498).The adsorption selectivity of porous graphite carbon for CH4/CO2 was calculated by ideal adsorption solution theory(IAST).The adsorption selectivity of C-COP-P-Mn reached 6.3 and 11.4 at T = 298 K,P =1 bar and 12 bar.At the same time,we used density functional theory(DFT)to calculate the interaction between C02 and metal sites,and then explained the selective arrangement of three kinds of graphite carbon for the mixed gas.2.Porous Aromatic Framework(PAF)with three-dimensional structure was synthesized with monomer Tetrakis(4-bromophenyl)methane by Yamamoto coupling reaction.After sulfonated,the material reacted with a metal salt to obtain a non-noble metal-modified covalent organic polymeric material.In this work,cobalt(Co)doped porous adsorbent was prepared by the method of post-treatment.FTIR proved the existence of SO3-functional groups.XPS and ICP-AMS proved the successful doping of metal elements.At 298 K and 1 bar,the CO2 adsorption capacity of PAF-1-SO3Co was 2.51 mmol·g-1,which was higher than that of the raw material(1.37 mmol·g-1).At the same time,the selectivity of PAF-1-SO3Co to mixed gas(CO2/CH4 =50/50)also increased from 3.00 to 14.27.The material owns very good structural and functional stability,which will be a promising material for carbon dioxide capture. |
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