Enhancement of CO2/N2 separation in MMMs by the regulation of nanofiller microenvironment

Abstract

Mixed-matrix membranes (MMMs) incorporating Metal-Organic Frameworks (MOFs) represent a promising approach for gas separation, which can combine the advantages of selective adsorbents and processable polymers, and display great potential in the gas separation process. However, the further application of MMMs is severely impeded owing to the non-ideal interface between fillers and polymer matrix. In this work, a series of MIL-101(Cr) nanofillers, equipped with different kinds of counter anions were introduced to regulate the chemical microenvironment of the MMMs and improve the interfacial relationship between inorganic filler and polymer. The filler of MIL-101-HNO3 exhibits improved dispersibility in solvents and heightened interface relationship with the polymer matrix (PIM-1) due to its optimal particle size and distinctive exposure of crystallographic planes. Moreover, gas sorption isotherms reveal that the MIL-101-HNO3 MOF show reduced N2 adsorption capacity. Therefore, the MOF filler of MMMs were optimized rationally by microenvironment regulate strategy, leading to the MIL-101-HNO3/PIM-1 MMMs achieve high CO2 permeability and exceptional CO2/N2 ideal selectivity (CO2 = 14879 barrer, CO2/N2 = 24.3), surpassing the latest 2019 upper bound. That makes MIL-101-HNO3/PIM-1 a potential candidate for the selective removal of CO2 from stack gas and provides new insights into the regulation of the MMMs nanofiller microenvironment.