Carbon Capture and Storage (CCS) strategies play a central role in mitigating carbon dioxide (CO2) emissions. Solid adsorbents for post-combustion carbon capture appear to be a promising solution due to their easier application into existing facilities [1]. Among the materials potentially able to overcome the state-of-the-art technology based on aqueous amines, Metal-Organic Frameworks (MOFs) attract an increasing attention due to the ease in tuning their structure toward a more selective CO2 binding and a lower energy consumption process. A peculiar subclass of MOFs is represented by compounds featuring phase-change accomplished adsorption events, usually evidenced by sudden increase in the adsorbed amount in a narrow pressure region, generating what is experimentally referred to as a S-shaped adsorption isotherm.[2] These materials can afford superior separation performance with a reduced energy penalty. We recently proposed a facile synthetic method to prepare a perfluorinated form of the well-known MIL53(Al) MOF (hereafter F4-MIL53).[3] The material was thoroughly characterized by several physico-chemical methods. In particular, experimental characterization techniques, such as powder XRD and thermogravimetric analysis, have been coupled with more advanced experimental tools, including spectroscopies (IR and SSNMR), volumetry and microcalorimetry, to finely study the F4-MIL53 features, in particular focusing on the role of fluorine atoms and, most of all, on the flexible behavior of this framework, a major peculiarity of the MIL53 family. Unexpectedly, the breathing capability of F4-MIL53, induced by both specific host-guest interactions and temperature, was detected by using different experimental techniques. Even if a similar behavior is already known for non-fluorinated MIL53, some interesting differences came out: i) thermally induced phase transition can be obtained at much higher temperatures in F4-MIL53 (ca. 500 K, with minimal hysteresis for the reverse transition compared to the non-fluorinated MOF); ii) adsorption induced phase transitions can be triggered by different adsorbates, including application-relevant molecules as CO2. The CO2 adsorption was studied with both volumetric and gravimetric adsorption-desorption measurements. The peculiar host-guest interaction, resulting in an enlargement of the pores, was responsible for a defined step in the isotherm in the 0-5 bar pressure range (T range = 195-313 K). Moreover, fast adsorption/desorption kinetics and complete reversibility makes F4-MIL53 an excellent candidate for applications in pressure-swing based capture-release processes. References [1] A. Samanta et al.., (2012), Post-Combustion CO2 Capture Using Solid Sorbents: A Review, Ind. Eng. Chem. Res. 51, 1438-1463. [2] A. Schneemann et al., (2014), Flexible metal-organic frameworks, Chem. Soc. Rev. 43 6062-6096. [3] D. Morelli Venturi, V. Guiotto et al., (2023), Solvent-free synthesis of a new perfluorinated MIL-53(Al) with a temperature-induced breathing effect, Mol. Syst. Des. Eng. 8, 586-590.
Disclosing the peculiar phase-change behavior of perfluorinated MIL53(Al) metal organic framework: the effect of temperature and CO2 adsorption
Lucia Calucci;
2023
Abstract
Carbon Capture and Storage (CCS) strategies play a central role in mitigating carbon dioxide (CO2) emissions. Solid adsorbents for post-combustion carbon capture appear to be a promising solution due to their easier application into existing facilities [1]. Among the materials potentially able to overcome the state-of-the-art technology based on aqueous amines, Metal-Organic Frameworks (MOFs) attract an increasing attention due to the ease in tuning their structure toward a more selective CO2 binding and a lower energy consumption process. A peculiar subclass of MOFs is represented by compounds featuring phase-change accomplished adsorption events, usually evidenced by sudden increase in the adsorbed amount in a narrow pressure region, generating what is experimentally referred to as a S-shaped adsorption isotherm.[2] These materials can afford superior separation performance with a reduced energy penalty. We recently proposed a facile synthetic method to prepare a perfluorinated form of the well-known MIL53(Al) MOF (hereafter F4-MIL53).[3] The material was thoroughly characterized by several physico-chemical methods. In particular, experimental characterization techniques, such as powder XRD and thermogravimetric analysis, have been coupled with more advanced experimental tools, including spectroscopies (IR and SSNMR), volumetry and microcalorimetry, to finely study the F4-MIL53 features, in particular focusing on the role of fluorine atoms and, most of all, on the flexible behavior of this framework, a major peculiarity of the MIL53 family. Unexpectedly, the breathing capability of F4-MIL53, induced by both specific host-guest interactions and temperature, was detected by using different experimental techniques. Even if a similar behavior is already known for non-fluorinated MIL53, some interesting differences came out: i) thermally induced phase transition can be obtained at much higher temperatures in F4-MIL53 (ca. 500 K, with minimal hysteresis for the reverse transition compared to the non-fluorinated MOF); ii) adsorption induced phase transitions can be triggered by different adsorbates, including application-relevant molecules as CO2. The CO2 adsorption was studied with both volumetric and gravimetric adsorption-desorption measurements. The peculiar host-guest interaction, resulting in an enlargement of the pores, was responsible for a defined step in the isotherm in the 0-5 bar pressure range (T range = 195-313 K). Moreover, fast adsorption/desorption kinetics and complete reversibility makes F4-MIL53 an excellent candidate for applications in pressure-swing based capture-release processes. References [1] A. Samanta et al.., (2012), Post-Combustion CO2 Capture Using Solid Sorbents: A Review, Ind. Eng. Chem. Res. 51, 1438-1463. [2] A. Schneemann et al., (2014), Flexible metal-organic frameworks, Chem. Soc. Rev. 43 6062-6096. [3] D. Morelli Venturi, V. Guiotto et al., (2023), Solvent-free synthesis of a new perfluorinated MIL-53(Al) with a temperature-induced breathing effect, Mol. Syst. Des. Eng. 8, 586-590.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
