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 purifi-cation 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.