Highly efficient separation of carbon dioxide by a metal-organic framework replete with open metal sites

Selective capture of CO2, which is essential for natural gas purification and CO2 sequestration, has been reported in zeolites, porous membranes, and amine solutions. However, all such systems require substantial energy input for release of captured CO2, leading to low energy efficiency and high cost. A new class of materials named metal-organic frameworks (MOFs) has also been demonstrated to take up voluminous amounts of CO2. However, these studies have been largely limited to equilibrium uptake measurements, which are a poor predictor of separation ability, rather than the more industrially relevant kinetic (dynamic) capacity. Here, we report that a known MOF, Mg-MOF-74, with open magnesium sites, rivals competitive materials in CO2 capture, with 8.9 wt. % dynamic capacity, and undergoes facile CO2 release at significantly lower temperature, 80 C. Mg-MOF-74 offers an excellent balance between dynamic capacity and regeneration. These results demonstrate the potential of MOFs with open metal sites as efficient CO2 capture media.