Influence of the functionalization of imidazole on its CO 2 uptake efficiency. A theoretical contribution

CO2 capture using silica-immobilized dicationic ionic liquids with magnetic and non-magnetic properties

The need to find alternative materials to replace aqueous amine solutions for the capture of CO2 in post-combustion technologies is pressing. This study assesses the CO2 sorption capacity and CO2/N2 selectivity of three dicationic ionic liquids with distinct anions immobilized in commercial mesoporous silica support (SBA- 15). The samples were characterized by UART-FTIR, NMR, Raman, FESEM, TEM, TGA, Magnetometry (VSM), BET and BJH. The highest CO2 sorption capacity and CO2/N2 selectivity were obtained for sample SBA@DIL_2FeCl4 [at 1 bar and 25 °C; 57.31 (±0.02) mg CO2/g; 12.27 (±0.72) mg CO2/g]. The results were compared to pristine SBA-15 and revealed a similar sorption capacity, indicating that the IL has no impact on the CO2 sorption capacity of silica. On the other hand, selectivity was improved by approximately 3.8 times, demonstrating the affinity of the ionic liquid for the CO2 molecule. The material underwent multiple sorption/desorption cycles and proved to be stable and a promising option for use in industrial CO2 capture processes.

Impact of the functionalization onto structure transformation and gas adsorption of MIL-68(In)

A series of functionalization -NH2, -Br and -NO2 has been performed on MIL-68(In) material in order to improve the porosity features of the pristine material. The functional groups grafted onto the ligand and the molar ratios of the ingredient indicate a profound influence on product formation. With the incremental amount of metal source, product structures undergo the transformation from MIL-68 to MIL-53 or QMOF-2. The situation is different depending on the variation of the ligands. Gas (N2, Ar, H2 and CO2) adsorption-desorption isotherms were systematically investigated to explore the impact of the functionalization on the porous prototypical framework. Comparison of adsorption behaviour of N2 and Ar indicates that the polar molecule exhibits striking interaction to N2 molecule, which has a considerable quadrupole moment. Therefore, as a probe molecule, Ar with no quadrupole moment is more suitable to characterize the surface area with the polar groups. Meanwhile, Ar adsorption result confirms that the negative influence on the surface area stems from the size of the substituting groups. The uptake of H2 and CO2 indicates that the introduction of appropriate polar organic groups can effectively enhance the adsorption enthalpy of relative gases and improve the gas adsorption capacity apparently at low pressure. The introduction of -NO2 is in favour of improving the H2 adsorption capacity, while the grafted -NH2 groups can most effectively enhance the CO2 adsorption capacity.

The effect of gme topology on multicomponent adsorption in zeolitic imidazolate frameworks

We employ a simulation approach to study the adsorption of single, binary and ternary mixtures on eight gme Zeolitic Imidazolate Frameworks (ZIFs) at 298 K. Four adsorbate fluids were considered; carbon dioxide, methane, nitrogen and water. We compute the high pressure adsorption density profiles inside the micropore channels of each crystal. The profiles are compared directly for the different structures and adsorbate components and used to highlight the influence of the imidazolate ligands on pure and competitive adsorption. ZIFs with long ligands reveal an additional, accessible to the fluid space detected for the first time. This is a wedged volume on one direction of the pore walls, shaped thus because the long ligands tilt in order to be connected. We estimate the pressure required for water to become the dominating competing adsorbate within different crystal cavities. The simulated data for CO₂ adsorption in ZIF69 strongly correlate with a set of Raman spectroscopy intensity values that correspond to the same adsorbate-adsorbent system.