Low-Energy CO2 Capture through Cooperative Adsorption
Top: CO2 is adsorbed via insertion into metal-amine bonds, as revealed by powder x-ray diffraction. 1D chains of ammonium carbamate are formed as the cooperative process propagates along the pore surfaces. Bottom: CO2 adsorption isotherms at 25, 40, 50, and 75 °C for Mg2 and CO2 show how the position of the step can be controlled by varying metal-amine bond strength.
Revealed an unprecedented cooperative mechanism for CO2 capture via its insertion into metal–amine bonds of metal-organic frameworks (MOFs).
Significance and Impact
Understanding the mechanism enables us to design new MOF adsorbents that can significantly reduce the energy required for CO2 capture from a power plant flue gas.
- Step-shaped adsorption isotherms were observed upon appending diamine molecule to sponge-like solid MOFs
- Through spectroscopic, diffraction, and computational methods, the isotherm step’s origin was shown to be insertion of CO2
- Insertion of CO2 at one site facilitates insertion at a neighboring site, leading to formation of ammonium carbamate chains
- The pressure at which the adsorption step occurs can be systematically tuned to minimize the energy used in CO2 separations