Mixed matrix membranes based on NbOF52− anion-pillared porous MOFs for efficient CO2 separation

Abstract

CO2 capture and storage technologies are crucial for environmental conservation and sustainable progress. To overcome the challenging trade-off between permeability and selectivity in polymeric CO2 separation membranes, we innovatively fabricated mixed matrix membranes (MMMs) by introducing three different NbOF52− anion-pillared porous metal–organic frameworks (MOFs), namely NbOFFIVE-2-Cu-i, NbOFFIVE-2-Ni-i, and NbOFFIVE-bpy-Ni. The CO2 capture performance of the three MOFs was investigated for the first time, and the ideal adsorption solution theory (IAST) method was used to predict the CO2 separation selectivity. Density functional theory (DFT) calculations confirmed that the interaction energy between NbOFFIVE-2-Cu-i and CO2 is the highest among the three MOFs. This is due to the optimal pore dimensions and strong Cδ+ … Fδ− electrostatic interaction between the C atoms in CO2 molecules and the F atoms in NOFFIVE-2-Cu-i. The introduction of the three MOFs into the MMMs led to an increase in CO2 solubility, resulting in enhanced CO2 permeability and selectivity. The MMM loaded with 2 wt% of NbOFFIVE-2-Cu-i exhibited exceptional CO2 permeability and CO2/N2 ideal selectivity values of 578 Barrer and 70, respectively, representing enhancements of 39 % and 29 % compared to neat membrane, and exceeding the upper bound established in 2019.