| Metal organic frameworks(MOFs),as a kind of new porous materials have attracted attention owing to their high specific surface area and adjustable pore size,as well as commercial interest due to their potential applications in storage and separation.One of the advantages of MOFs compared to other microporous materials,such as activated carbons,is their ability to exhibit a variety of pore surface properties as a result of the controlled incorporation of organic functional groups into the pore walls.Coordination pillared layers(CPLs)are materials adjusting the size of the pore size by changing the length of ligand to regulate the performance of gas adsorption separation.The potential application of CPLs,Cu2(pzdc)2L·H2O(pzdc=2,3-pyrazinedicarboxylic acid,L = ligand)in ethylene purification,methane concentration and acetylene purification was studied in this paper.Meanwhile the regulation of pore size on the adsorption separation performance of the above gas was studied.Firstly,porous metal organic frameworks CPL-1,CPL-2,CPL-4,CPL-5 and CPL-6(pyrazine,4,4-dipyridyl,4,4’-azo-dipyridine,4,4’-vinylenedipyridine,N-(pyridin-4-yl)nicotinamide as ligand)were prepared by solvent diffusion method.Their stability,structure and porosity were characterized by thermogravimetric analysis(TGA),powder X ray diffraction(PXRD)and low temperature CO2 adsorption.It was found that the specific surface area of CPLs was 414～607 m2 g-1.XRD results show that the materials remain unchanged after exposed to the air for one week.TGA results showed that CPLs had good thermal stability under the temperature of 200 ℃.Secondly,the static adsorption properties of CPLs for acetylene and ethylene were measured,and the selectivity of acetylene ethylene adsorption was calculated by IAST theory.Both of the CPLs have high separation selectivity,which is mainly attributed to the formation of a strong hydrogen bond between acetylene molecules and the structure.The C2H2/C2H4 adsorption selectivity of CPL-1 is 27 at 25 ℃ and 100 kPa,which is better than SIFSIX-1-Cu,M’MOF-3a and UTSA-100a.This is because of the size of CPL-1(4 A)is just between the kinetic diameter of acetylene(3.3 A)and ethylene(4.2 A).After soaked in water for 12 h,24 h,48 h and 1 week,CPL-1 had no changes.At the same time,the gas adsorption experiment further showed that the high stability of CPL-1.The C2H2/C2H4 transient breakthrough simulation further verified the efficient separation performance of CPLs,indicating the application in industrial production.Thirdly,the static adsorption properties of CPLs for carbon dioxide,methane and nitrogen were measured,and the selectivity was calculated by IAST theory.CPLs has high adsorption capacity of carbon dioxide and selectivity of CO2/N2 and CO2/CH4 because of the pore size.The CO2/CH4 adsorption selectivity of CPL-1 is 59,and the CO2/N2 adsorption selectivity is 114 at 25 ℃ and 100 kPa,which is better than SIFSIX-2-Cu-i and UTSA-16.The CO2/N2 and CO2/CH4 transient breakthrough simulation further verified the efficient separation performance of CPLs,indicating the application in Carbon dioxide capture and natural gas purification.Finally,the selectivity of acetylene ethylene adsorption was calculated by IAST theory.Both of the CPLs have high separation selectivity,which is also attributed to the formation of a strong hydrogen bond between acetylene molecules and the structure.The C2H2/CO2 adsorption selectivity of CPL-1 is 38 at 25 ℃ and 100 kPa,which is better than almost all MOFs such as HOF-3a.The C2H2/CO2 transient breakthrough simulation further verified the efficient separation performance of CPLs,indicating the application in industrial production. |
