Binary CO2/H2O adsorption on CO2 capture metal-organic frameworks CALF-20, Al-Fumarate and CAU-10H using microscale dynamic column breakthrough

This study reports the development of a quantitative microscale dynamic column breakthrough instrument to measure the competitive equilibrium loadings of CO2 and H2O isotherms on small quantities (≈ 200 mg) of metal-organic framework (MOF) samples. The binary CO2 and H2O equilibria were measured on CALF-20, Al-Fumarate and CAU-10-H, three MOFs of interest for post-combustion CO2 capture at 30 °C. For Al-Fumarate and CAU-10-H, pure CO2 and H2O competition was measured at 30 °C. For CALF-20, extensive mapping of the impact of CO2 concentration and various water concentrations was performed at 30 °C. All three MOFs feature an S-shape H2O isotherm and a type-I CO2 isotherm. In all three MOFs, the CO2 capacity is generally retained towards the left of the inflection point of the H2O isotherm. Water capacity drops after the inflection point, and the magnitude of the drop depends on the sharpness of the H2O isotherm. On the one hand, for Al-Fumarate and CAU-10-H the H2O isotherm was unaffected by CO2. On the other hand, for CALF-20, the presence of CO2 impacts the H2O water isotherm, extending the relative humidity range over which the CO2 capacity is retained. Using the ideal adsorbed solution theory to predict the binary equilibria revealed deviations from ideality for all three MOFs.