Metal–organic frameworks with potential for energy-efficient adsorptive separation of light hydrocarbons

The separation of hydrocarbons with carbon numbers in the 1-3 range is of great significance in the purification of natural gas, production of ethylene and propylene with the required 99.5%+ purity levels as feeds to polymerization reactors, and separation of ethyne from mixtures with ethylene. In this study the performances of a total of 19 different MOFs, carefully selected to span a wide range of functionalities, were evaluated for a variety of separation tasks. For all separation tasks investigated, MOFs with high density of open metal sites, CoMOF-74, MgMOF-74, and FeMOF-74, have significantly better separation potential than other MOFs, ZIFs or zeolites that have been suggested in the literature. Of particular significance is the possibility offered by CoMOF-74, MgMOF-74, and FeMOF-74 for "fractionating" a 6-component CH4/C2H2/C2H4/C2H6/C3H6/C3H8 mixture to yield individual pure components. Such separations are likely to have a significant industrial impact, resulting in significant energy savings when compared to current technologies that rely on distillation.