NKMOF-2 With Highly Selectivie Gas Capture And Separation Performance By Anion Post-modification

The pore system?pore size,shape,and function?of metal-organic framework?MOFs?can be fine-tuned as needed,it is a kind of mixed crystalline material with infinite structure and chemical diversity and has the greatest potential for separation in porous materials.NKMOF-2-Cl is a Metal-Organic framework material that is formed by the coordination of bivalent copper ions and organic ligand Hcpt,it has free chloride ions which can be post-modified into a variety of monovalent anions in the pore channels.In this paper,the application value of NKMOF-2-X materials in the fields of carbon dioxide capture,natural gas purification and acetylene/carbon dioxide separation were studied,and the regulation of different anions on the above gas separation were discussed.NKMOF-2-Cl was firstly synthesized by hydrothermal method,after that,Cl^-ions was exchanged into F^-,Br^-,I^-,BF₄^-,and NO₂^-ions by anionic post-modification method,five MOFs were obtained,including NKMOF-2-F,NKMOF-2-Br,NKMOF-2-I,NKMOF-2-BF₄ and NKMOF-2-NO₂,the analysis of single crystal structure and PXRD spectra confirmed that they were isomorphic materials.Afterwards,ion exchange ratio was determined by ion chromatography,ICP-OES:Br^-ion can exchange 100%Cl^-ion,F^-and I^-ions can exchange 2/3 of Cl^-ions,BF₄^-and NO₂^-ions only exchange one free Cl^-ion.The CO₂ isothermal adsorption curve at 196K indicated that the hole of the materials that are ultramicroporous materials were between 3.9-4.6?.In chapter three,we tested the adsorption isotherms of CO₂,CH₄ and N₂ in NKMOF-2-X materials,experiments show that different anions can adjust the amount of CO₂ adsorption,BF₄^-anion enhance effectively the adsorption capacity of gases.The ability of different anions in the pore channels of NKMOF-2-X materials to capture carbon dioxide was investigated by the enthalpy of adsorption of carbon dioxide and methane.The adsorption selectivity of NKMOF-2-X material at 100kPa for the mixed gases 15/85 CO₂/N₂ and 50/50 CO₂/CH₄ was calculated by IAST theory,their separation ratio exceeds that of most MOFs materials.NKMOF-2-X materials show good separation effect in the breakthrough experiments of 15/85 CO₂/N₂ and 50/50CO₂/CH₄ mixture gases.Among them,NKMOF-2-BF₄ has the best performance and is expected to be used in the capture of carbon dioxide and the purification of methane in industry.Finally,it is found that different anions have different proportions of regulating acetylene and carbon dioxide by the adsorption isotherms of C₂H₂ and CO₂ single-component gas of NKMOF-2-X materials.Q_st of C₂H₂ and CO₂ in NKMOF-2-X indicates that different anions exert different forces on them.Based on IAST theory,the adsorption selectivity of NKMOF-2-X materials on C₂H₂/CO₂ with a volume ratio of 50/50 was calculated at 100kPa,the separation ratio of NKMOF-2-BF₄ was the highest.The experiment of 50/50 C₂H₂/CO₂ mixed gas penetration shows that NKMOF-2-X materials can effectively separate carbon dioxide and acetylene.NKMOF-2-BF₄ has the best performance and is expected to be used in the separation of acetylene and carbon dioxide.