Hydrocarbon Separations in a Metal-Organic Framework with Open Iron(II) Coordination Sites

The energy costs assocd. with large-scale industrial sepn. of light hydrocarbons by cryogenic distn. could potentially be lowered through development of selective solid adsorbents that operate at higher temps. Here, the metal-org. framework Fe2(dobdc) (dobdc4- : 2,5-dioxido-1,4-benzenedicarboxylate) is demonstrated to exhibit excellent performance characteristics for sepn. of ethylene/ethane and propylene/propane mixts. at 318 K. Breakthrough data obtained for these mixts. provide exptl. validation of simulations, which in turn predict high selectivities and capacities of this material for the fractionation of methane/ethane/ethylene/acetylene mixts., removal of acetylene impurities from ethylene, and membrane-based olefin/paraffin sepns. Neutron powder diffraction data confirm a side-on coordination of acetylene, ethylene, and propylene at the iron(II) centers, while also providing solid-state structural characterization of the much weaker interactions of ethane and propane with the metal.