Identification of Metal-Organic Frameworks for near Practical Energy Limit CO₂ Capture from Wet Flue Gases: An...

Metal-organic framework (MOF) materials have attracted significant attention as solid sorbents for low energy CO₂ capture with adsorption-based gas separation processes. In this work, an integrated screening workflow combining a series of atomistic and process simulations was applied to identify promising MOFs for a 4-step pressure-vacuum swing adsorption (P/VSA) process at three different CO₂ flue gas compositions (6%, 15% and 35%). Starting from 55,818 unique experimentally characterized MOFs, ∼19k porous MOFs were investigated via atomistic grand canonical Monte Carlo (GCMC) simulations and machine learning model-based process optimizations to accelerate the screening of a large candidate database. Thousands of MOFs were identified for each of the CO₂ compositions tested that could achieve within 4% of the practical energy limit of dry CO₂ capture for the P/VSA process while still meeting the 95% CO₂ purity and 90% recovery constraints. From this pool, 3D MOFs without open metal sites were subjected to the multicomponent (CO₂/N₂/H₂O) GCMC simulations at 40% relative humidity. Based on these simulations, hundreds of MOFs were identified at each CO₂ composition that could retain 90% of their CO₂ capture at this humidity while also adsorbing a minimal amount of water. A geometric analysis of these high performing materials revealed that narrow, straight 1D-channels were a common structural motif for low energy wet flue gas CO₂ capture with P/VSA.