Molecular Simulation Of Metal-organic Frame-works For O₂/N₂ And CO₂/N₂ Separations

The combustion of fossil fuels caused the rapid rise of global CO₂ emission.Carbon capture and storage(CCS)technology is the key to reduce CO₂ emissions.Among CCS technologies,post-combustion carbon capture are more promising because of their low cost and facile reformation of current coal-fired power plants.Air separation and CO₂ capture are the key for post-combustion CO₂ capture.Metal-organic frameworks(MOFs)show great potential in air separation and CO₂ capture owing to their ultra-high surface area and porosity.However,there is an urgent need to identify high-performing candidates from a large number of MOFs.Therefore,high-throughput computational screening based on mo-lecular dynamics(MD)and grand canonical monte carlo(GCMC)molecular simulation was conducted in this work to identify potential MOFs for air separation and CO₂ capture of post-combustion carbon capture.For air separation,high-throughput computational screening was implemented to ex-plore the O₂/N₂ separation performance of 2932 MOFs as adsorbents and membranes.Based on the O₂/N₂ selectivity and O₂ working adsorption capacity,20 top-performimg MOF ad-sorbents were identified,among which the highest O₂/N₂ selectivity is 2.17.According to O₂/N₂ membrane selectivity and O₂ permeability,19 promising MOF membrane have been selected,among which the highest membrane selectivity is 5.18 that is about 15%higher than the polymer membrane PIM-7.More importantly,the O₂ permeability is improved by nearly two orders of magnitude.In addition,we also found that high-performing MOFs have small largest cavity diameter(LCD),small accessible surface area(ASA)and LCD/pore lim-iting diameter(PLD)=1.LCD,LCD/PLD,ASA and available pore volume(V_a)impose significant impacts on the O₂/N₂ separation performance of MOF adsorbents,while LCD and LCD/PLD play more important roles in the membrane separation performance of MOFs.For CO₂ capture,to further improve the CO₂ capture performance of MOFs,ionic liq-uids(ILs)are incoporated into MOFs to improve CO₂ capture performance.However,IL/MOF composites database for high-throughput computational screening has not been reported.Therefore,we explores the reliable model of IL/MOF composites for the IL/MOF composite database construction.The random model(ILs randomly were inserted into MOF)and the cluster model(ILs blocked MOF specific pores)were established.Their pore size distribution and CO₂ uptake were calculated and compared with the experimental measured results.Compared with the random model,the pore size distribution and CO₂ uptake of the cluster model are more comparable with the experiment reults,suggesting the reliability of cluster model for IL/MOF composites This study laid the foundation for the construction of IL/MOF composites database and high-throughput computational screening of IL/MOF composites for CO₂ capture.