Effect of Fe open metal site in metal‐organic frameworks on post‐combustion CO2 capture performance

Iron open metal site in metal‐organic frameworks, MIL‐88A and MIL‐127(Fe), was tested to investigate its performance on CO2 separation from a binary mixture CO2/N2 under simulated post‐combustion system. The sorption experiment tests were conducted via a fixed‐bed reactor with different temperatures ranging between 30°C and 60°C at atmospheric pressure. Maximum CO2 sorption capacity was observed at low temperature of 30°C, where 5.24 mmol could be adsorbed by one gram of MIL‐127(Fe) and 4.95 mmol CO2 could be adsorbed by one gram of MIL‐88A. The presence of moisture in the gas mixture affected CO2 sorption capacity by reducing CO2 capacity as high as 0.5 mmol CO2 per one gram sorbent. In this work, a dynamic breakthrough model was applied to investigate adsorption behavior of the metal‐organic frameworks (MOFs) and of the system. The predicted model showed good agreement with experimental results; the Langmuir isotherm model fitted well with our sorption system, suggesting one molecule of CO2 is held at localized sites of the MOFs, which plausibly be at unsaturated Fe2+ metal ion site. Rate of sorption was found to increase with increasing sorption temperature for either intra‐particle diffusivity or external mass transfer. Our study suggests that the MOFs containing Fe open metal sites offer an outstanding prospective for CO2 sorption and both MIL‐88A and MIL‐127(Fe) are good representatives applied for post‐combustion CO2 capture.