Mixed matrix membranes (MMMs) composed of NUS-8 metal-organic framework (MOF) nanosheets dispersed into a polymer of intrinsic microporosity 1 (PIM-1) polymer matrix are known to be promising candidates for CO2/N2 separation because of a solubility-driven separation mechanism. In this work, we predict that a chemical functionalization of the organic linker of NUS-8 by a CO2-philic function confers an even better separation performance to the resulting MMM. Our simulations revealed that the NUS-8-CO2H/PIM-1 composite exhibits a 3-fold increase in CO2/N2 selectivity versus the NUS-8/PIM-1 analogue while achieving a high CO2 permeability (6700 barrer). We demonstrated that this improved level of performance is due to an increase both in the total MOF/polymer interfacial pore volume and in the CO2-affinity due to the chemical functionalization. These results suggest that an appropriate choice of chemical functionalization of a MOF is a promising strategy to improve gas separation performances for MMM composites that exhibit a solubility-driven separation mechanism.
Keywords: Monte Carlo; adsorption; metal−organic frameworks; non-equilibrium molecular dynamics; polymer-based mixed matrix membranes.