Carbon dioxide capacity retention on elastic layered metal organic frameworks subjected to hydrothermal cycling

Adsorption of carbon dioxide on elastic layered metal-organic frameworks (ELMs) was investigated during and after exposure to water. Two ELM variants, ELM-11 and ELM-12, were contacted with water vapor and the impact of cyclical exposure on the CO2 capacity of the adsorbents was observed. ELM-11 was found to lose CO2 capacity with each successive exposure to water, whereas ELM-12 retained CO2 capacity through four exposure cycles. Density functional theory calculations were performed to interpret these observations. Changing the counter-ion from the simple tetrafluoroborate (BF4−) to the larger and more complex trifluoromethanesulfonate (CF3SO3−) anion expands the number of potential binding sites for adsorbate molecules. While CO2 directly competes with other adsorbates for binding sites in ELM-11, CO2 does not directly compete with other adsorbates in ELM-12 due to its preference for direct interaction with both fluorine and oxygen atoms in CF3SO3−.