Computational Screening of Metal–Organic Frameworks\nfor Membrane-Based CO₂/N₂/H₂O Separations:\nBest Materials for Flue Gas Separation

Abstract

It\nhas become a significant challenge to select the best metal–organic\nframeworks (MOFs) for membrane-based gas separations because the number\nof synthesized MOFs is growing exceptionally fast. In this work, we\nused high-throughput computational screening to identify the top MOF\nmembranes for flue gas separation. Grand canonical Monte Carlo and\nmolecular dynamics simulations were performed to assess adsorption\nand diffusion properties of CO₂ and N₂ in 3806\ndifferent MOFs. Using these data, selectivities and permeabilities\nof MOF membranes were predicted and compared with those of conventional\nmembranes, polymers, and zeolites. The best performing MOF membranes\noffering CO₂/N₂ selectivity > 350 and CO₂ permeability > 10⁶ Barrer were identified.\nTernary\nCO₂/N₂/H₂O mixture simulations were\nthen performed for the top MOFs to unlock their potential under industrial\noperating conditions, and results showed that the presence of water\ndecreases CO₂/N₂ selectivity and CO₂ permeability of some MOF membranes. As a result of this stepwise\nscreening procedure, the number of promising MOF membranes to be investigated\nfor flue gas separation in future experimental studies was narrowed\ndown from thousands to tens. We finally examined the structure–performance\nrelations of MOFs to understand which properties lead to the greatest\npromise for flue gas separation and concluded that lanthanide-based\nMOFs with narrow pore openings (<4.5 Å), low porosities (<0.75),\nand low surface areas (<1000 m²/g) are the best materials\nfor membrane-based CO₂/N₂ separations.