Gas Adsorption And Separation Properties Of Hydrogen Bonded Organic Framework Materials

Coalbed methane is a gas resource co-produced with coal,and is a hydrocarbon gas stored in coalbeds.Coalbed methane,commonly known as“mashgas”,is mainly composed of methane,which is also mixed with a large amount of carbon dioxide.If the mined coalbed methane is used for combustion,it will cause a great waste of energy,and further lead to aggravation of environmental problems.Converting the methane in the coalbed methane into high-value chemicals will effectively avoid the above problems.Therefore,removing carbon dioxide impurities in coalbed methane and improving the purity of methane have become a new and challenging problem.Hydrogen-bonded organic frameworks(HOFs)are important porous materials that can self-assemble via hydrogen bonding between organic or metal-organic linkers.Due to the reversibility and flexibility of hydrogen bonding,HOFs exhibit high crystallinity,solution processability,and easy healing and purification.To achieve permanent porosity in HOFs,stable and robust open frameworks can be constructed by choosing rigid molecular building blocks and hydrogen-bonding units with strong hydrogen-bonding interactions,where,through backbone interpenetration and other types of weak intermolecular Interactions,such as?-?interactions,can further enhance the stability of the framework.Here,the great potential of HOF materials as multifunctional materials has broad application prospects in several fields of gas storage and separation,molecular recognition,electrical and optical materials,chemical sensing,catalysis,and biomedicine.In view of this,this paper takes hydrogen-bonded organic framework materials as the research object,and synthesized two representative HOF materials,which can effectively separate the mixed gas of CO₂/CH₄ and CO₂/N₂ at 298 K.Its structure was characterized by XRD,FT-IR and specific surface area and pore size analysis,and its stability,gas adsorption and separation performance were also characterized.1.The hydrogen-bonded supramolecular metal-organic framework material HOF-21 was successfully synthesized by the interfacial synthesis method,and its structure was determined by X-ray powder diffraction and Fourier transform infrared spectroscopy,and the single component of CO₂,CH₄ and N₂ was determined by the material.Adsorption isotherms of gases.The experimental results show that the BET surface area of HOF-21 is 282.46 m~2 g^-1.Based on the Ideal Adsorption Soluton Theory(IAST)calculation,under the conditions of 298K and 1bar,the separation selectivity of HOF-21 for mixed gas 50:50 CO₂/CH₄ and CO₂/N₂ were 59 and 259,respectively.The experimental results of fixed bed dynamic adsorption of two-component gas mixture CO₂/CH₄(50:50 and 20:80,v/v)and CO₂/N₂(50:50 and 20:80,v/v)show that HOF-21 can achieve effective separation of the mixed gas of CO₂/CH₄ and CO₂/N₂ at 298 K.2.The hydrogen-bonded organic framework material HOF-BTB was successfully synthesized by solvothermal synthesis method,and its structure was determined by X-ray powder diffraction and Fourier transform infrared spectroscopy.The stability test results showed that the material has good thermal stability and solvent.stability.Based on its N₂ adsorption isotherm at 77 K,its BET surface area was calculated to be 381.79 m~2 g^-1.Based on the adsorption isotherms of CO₂,CH₄ and N₂ single-component gases,the virial equation simulation results preliminarily verify that the material has selective adsorption properties for CO₂/CH₄ and CO₂/N₂ mixed gases.Finally,it is confirmed that the material can effectively separate the mixed gas of CO₂/CH₄ and CO₂/N₂ through penetration experiments.