Metal-Organic Framework (MOF)-based Adsorbents for Gas Separations in the Petrochemicals Industry

Facile separation of Carbon Monoxide (CO) from Dinitrogen (N2) has the opportunity to provide a new supply of CO from flue gases. CO is an important resource due to its use within chemical industry as a stock fed for methanol and other hydrocarbons. Current CO/N2 separation involves energy intense cryogenic separation which is impractical for the flue gas use1. An alternative technique, metal organic frameworks (MOFs), has shown promise in the separation of a number of common gases such as H22, CO23, N24, CH43, water vapour, as well as more exotic toxic gases such as sarin5,6. Some interest has been shown in the separation of CO/N2 however this research has been eclipsed by alternative atmospheric gases.
Separation of CO from N2 has been shown to be difficult due to similar chemical characteristics such as boiling point and physical size. Instead we can take advantage of CO's propensity to backbond with metal centres via n-antibonding orbitals. This leads to a logical conclusion that a successful MOF for the separation of CO from N2 will be dependent on the metal centre of the MOF and the amount of accessible metal sites for gas adsorption. Density functional theory (DFT) calculations have shown that a number of metals are of interest for the adsorption of CO7,8 whilst a number of approaches have been shown to create additional accessible metal sites within the structure of the MOF9,10,11. More recently the doping of MOFs with more reactive metal ions has shown increases in the CO selectivity12.
Using these ideas as a foundation, we hope to develop a selection of MOFs suitable for the separation of CO from N2 by selectively adsorbing and desorbing CO to provide a high purity resource.