A Bio-Metal-Organic Framework for Highly Selective CO2 Capture: A Molecular Simulation Study

A recently synthesized bio-metal-organic framework (bio-MOF-11) is investigated for CO2 capture by molecular simulation. The adenine biomolecular linkers in bio-MOF-11 contain Lewis basic amino and pyrimidine groups as the preferential adsorption sites. The simulated and experimental adsorption isotherms of pure CO2, H-2, and N-2 are in perfect agreement. Bio-MOF-11 exhibits larger adsorption capacities compared to numerous zeolites, activated carbons, and MOFs, which is attributed to the presence of multiple Lewis basic sites and nanosized channels. The results for the adsorption of CO2/H-2 and CO2/N-2 mixtures in bio-MOF-11 show that CO2 is more dominantly adsorbed than H-2 and N-2. With increasing pressure, the selectivity of CO2/H-2 initially increases owing to the strong interactions between CO2 and the framework, and then decreases as a consequence of the entropy effect. However, the selectivity of CO2/N-2 monotonically increases with increasing pressure and finally reaches a constant. The selectivities in bio-MOF-11 are higher than in many nanoporous materials. The simulation results also reveal that a small amount of H2O has a negligible effect on the separation of CO2/H-2 and CO2/N-2 mixtures. The simulation study provides quantitative microscopic insight into the adsorption mechanism in bio-MOF-11 and suggests that bio-MOF-11 may be interesting for pre- and post-combustion CO2 capture.