Unlocking the Effect of HO on CO Separation Performance of Promising MOFs Using Atomically Detailed Simulations.

Metal organic frameworks (MOFs) have been considered as potential adsorbents for adsorption-based CO/CH and CO/N separations because of their high CO selectivities and high working capacities. HO in flue gas and natural gas streams affects the gas uptake capacities of MOFs. However, the presence of HO is commonly neglected in high-throughput computational screening studies while assessing the CO separation performances of MOFs. In this study, the impact of the presence of HO on the CO separation performances of 13 MOFs that were previously identified as the best adsorbent candidates among several thousands of MOFs was examined. Molecular simulations were used to compute selectivity, working capacity, regenerability, and adsorbent performance score (APS) of MOFs considering separation of binary CO/CH, CO/N, and ternary CO/CH/HO and CO/N/HO mixtures. The results showed that introduction of HO as the third component into binary CO/CH and CO/N mixtures significantly affected the adsorbent evaluation metrics of MOFs that have strong affinity toward HO because of the presence of specific functional groups and/or extra framework anions in the framework. Remarkable increases in CO/N selectivities of MOFs were observed in the presence of HO. On the other hand, simulations performed using MOFs that are preloaded with HO to mimic the exposure of MOFs to humidity prior to gas adsorption revealed drastic decreases in CO working capacities and APSs of MOFs both for CO/CH and CO/N separations. These results will be useful for the design and development of efficient MOF adsorbents for CO capture under humid conditions.