Mg/DOBDC MOF Functionalized with Ethylene Diamine for Improved Resistance to Humidity in CO2 Capture Applications

With the steady rise in carbon dioxide levels, there has been an increased interest in various methods of separating CO2 from flue gas, as one of the major sources of carbon emissions is the burning of fossil fuels. Capturing CO2 before it reaches the atmosphere could mitigate its possible effects on climate change. Many materials currently used in CO2 separation consume a lot of energy and produce harmful by-products. Metal organic frameworks (MOFs) are crystalline structures combining metal ions with organic molecules, and they could provide a safer, less expensive alternative to separate CO2 from various gases. However, the effectiveness of MOFs for CO2 capture decreases along with the degradation of their structure in the presence of humidity, which is another major component of flue gas.

To minimize the effects of humidity to the structure and CO2 capture performance of MOFs, this work investigates the addition of amine functional groups to improve the stability of the MOF structure, using Mg-MOF-74. Amines are currently used as a chemical absorbent in CO2 capture. Mg-MOF-74â??s properties were first examined using x-ray diffraction and BET surface area analysis, as well as CO2 capture tests before and after steam treatments. This MOF was then synthesized and functionalized with amine groups at open coordinate sites in the hope of improving CO2 capture and protect the MOF from degradation. It was found that the modified MOF had improved CO2 capture, and was more resistant to degradation in the presence of humidity. Strikingly, the MOF showed no loss in capacity after extreme steam treatments when functionalized with amine groups, suggesting that the addition of amines could successfully mitigate the effects of humidity on the MOF structure.