Fe2(dobdc) has a metal-organic framework with a high density of coordinatively-unsaturated FeII centers lining the pore surface. It can be effectively used to separate O2 from N2 and in a number of additional separation applications based on selective, reversible electron transfer reactions. In addition to being an effective O2 separation material, it can be used for many other processes, including paraffin/olefin separation, nitric oxide/nitrous oxide separation, acetylene storage, and as an oxidation catalyst.