Assembling ionic liquids in MOF “Monomer” based membranes to trigger CO2/CH4 separation

Abstract

The advantages of ionic liquids (ILs) in the selective adsorption of CO₂ can improve the CO₂-selective separation performance of IL-modified membranes. Herein, a facile post-modification strategy using ILs has been developed for filling the interspace of MOF “monomer” based membranes to enhance the CO₂/CH₄ sieving performance. The membranes constructed via the interfacial polymerization of MOF “porous monomers” and trimesoyl chloride (TMC) have nanoscale interspaces, which limit the performance of these membranes in the field of precise CO₂/CH₄ sieving. The addition of ILs with high CO₂ affinity filled these interspaces between the MOF and TMC monomers, resulting in a CO₂/CH₄ selectivity of 35 for the modified membranes compared with the non-selectivity of the pristine membrane. Furthermore, the hydrogen-bond interaction between ILs and the membrane improves the separation stability and avoids the loss of ILs during gas permeation. After long-term continuous gas separation tests, the membrane can maintain stable CO₂/CH₄ selectivity. Therefore, a post-modification membrane using ILs is highly desirable for enhancing the gas separation performance of MOF “porous monomer” based membranes for natural gas purification applications.