In-situ grafted amine functionalized metal-organic frameworks for CO2 capture: Preparation and bench-scale performance evaluation

The work includes the preparation of zirconium fumarate (ZrFu) metal-organic framework (MOF) and investigation of the CO2 capture performance of the material. The CO2 adsorption experiments were performed in a bench-scale flow reactor with a simulated flue gas mixture. To enhance the CO2 capture capacity of the ZrFu material, two polydentate amines, namely diethylenetriamine (DETA) and tetraethylenepentamine (TEPA) were incorporated into the ZrFu by an in-situ grafting method. The effects of adsorption temperature, pressure, amine loading, and CO2 concentration in the feed gas mixture on CO2 capture were examined. The obtained value of the CO2 uptake capacity of the pristine ZrFu is 73 g CO2/kg sorbent at 30 oC under atmospheric pressure. Among the amine-modified MOFs, the DETA-modified ZrFu (10-DETA-ZrFu) showed a maximum adsorption capacity of 86 g CO2/kg sorbent. It is also noted that at 90 degrees C, the CO2 adsorption capacity of the material is 57 g CO2/kg sorbent, which is about 67% of the capture capacity at 30 degrees C. This demonstrates that the MOFs can capture and retain the CO2 molecules inside the MOF moiety even at higher temperatures. The study also revealed that the synthesized MOFs are chemically stable with about 10% moisture environment. The prepared MOFs exhibited admirable thermo-chemical stability up to around 150 degrees C. Among the studied isotherm models, the Langmuir model showed a good agreement with the experimental data for lower values of adsorption pressure. The estimated value of adsorption energy for the adsorption of CO2 on ZrFu is 6.9 kJ/mol at 30 degrees C.