Study On Preparation Of MOFs And Their Adsorption Storage Performance For Methane

Adsorption storage technology is the basis for distributed storage of natural gas,which is of great significance to the marketization of natural gas vehicles.Metal-organic frameworks(MOFs)are ideal materials for natural gas adsorption storage due to their large specific surface area and large pore volume and good structure controllability.In this paper,two adsorbents,MOF-5 and HKUST-1,were synthesized,and the adsorption storage performances of methane were studied.The adsorbent MOF-5 was synthesized by solvothermal method.The optimized synthesis conditions were as follows:n(Zn(NO3)2·6H2O):n(H2BDC):n(DMF)=2:1:160,the crystallization temperature of 150?,the crystallization time of 24 h and activation treatment using chloroform for 3d.The methane adsorption capacity of the synthesized MOF-5 was 6.0 mmol/g at 25?.Water had an adverse effect on the adsorption performance of synthesized MOF-5.The specific surface area of MOF-5 decreased from 1125 m2/g to 308 m2/g,and the pore volume decreased from 0.46 cm3/g to 0.21 cm3/g after 1wt%H2O was adsorpted,.The adsorbent HKUST-1 was also synthesized by solvothermal method.The optimized synthesis conditions were as follows:n(Cu(NO3)2 · 3H2O):n(H3BTC):n(DMF):n(Ethanol):n(H2O)=1.7:1:46:60:100,the crystallization temperature of 80? and the crystallization time of 24 h.The methane adsorption capacity of HKUST-1 was 11.9 mmol/g at 25?.Acid ligand modification could increase the methane adsorption capacity of HKUST-1.When n(HAc):n(H3BTC)=11.0,the methane adsorption capacity reached 12.6 mmol/g.The specific surface area increased from 1499 m2/g to 1990 m2/g,and the pore volume increased from 0.55 cm3/g to 0.72 cm3/g.Adsorption isotherms of methane in MOF-5 and HKUST-1 could be described by Langmuir-Freundich model.At 3.5 MPa,the adsorption heat of methane in MOF-5 and HKUST-1 were 12.56 kJ/mol and 12.25 kJ/mol,respectively.The diffusion behavior of methane in MOFs adsorbent was simulated using the molecular dynamics method.The maximum self-diffusion coefficient of methane in HKUST-1 was 7.34×10-9 m2/s.