Robust ultra-microporous metal-organic frameworks for highly efficient natural gas purification

The development of highly efficient separation technology for the purification of natural gas by removing ethane(C_(2)H_(6))and propane(C_(3)H_(8))is a crucial but challenging task to their efficient utilization in the chemical industry and social life.Here,we report three isomorphic ultra-microporous metal-organic frameworks(MOFs),M-pyz(M=Fe,Co,and Ni,and pyz=pyrazine)referred to as Fe-pyz,Co-pyz,and Ni-pyz,respectively,which possess high density of open metal sites and suitable pore structure.Compared with the benchmark materials reported,M-pyz not only has high adsorption capacities of C_(2)H_(6)and C_(3)H_(8)at low pressure(up to 51.6 and 63.7 cm^(3)·cm^(−3)),but also exhibits excellent C_(3)H_(8)/CH_(4)and C_(2)H_(6)/CH_(4)ideal adsorption solution theory(IAST)selectivities,111 and 25,respectively.Theoretical calculations demonstrated that the materials’separation performance was driven by multiple intermolecular interactions(hydrogen bonding interactions and van der Waals effect)between gas molecules(C_(2)H_(6)and C_(3)H_(8))and the M-pyz binding sites.And,dynamic breakthrough experiments verified the superior reusability and practical separation feasibility for the ternary CH_(4)/C_(2)H_(6)/C_(3)H_(8)mixtures.Furthermore,M-pyz can be synthesized rapidly and on a large scale at room temperature.This work presents a series of promising MOFs adsorbents to efficiently purify natural gas and promotes the industrial development process of MOFs materials.