ZIF-8 modified with 2-undecylimidazolate as filler for mixed matrix membranes for CO2 separation

Abstract

A novel modification of zeolitic imidazolate framework-8 (ZIF-8) with 2-undecylimidazolate (umIm) was explored to enhance its hydrophobic character and improve its compatibility with polymer of intrinsic microporosity PIM-1 when incorporated as a filler in mixed matrix membranes (MMMs). In addition to the study of the best conditions to exchange the structural ligand of ZIF-8 by umIm and the characterization (by FTIR, RMN, XRD, TGA, N₂ adsorption and TEM) of the obtained material, comparative analyses were conducted using MMMs containing the original ZIF-8 and the modified version. Different loadings were applied to study the impact on gas separation properties. Remarkably, the MMM with the modified ZIF-8 demonstrated superior performance surpassing the Robeson upper bound line of 2008 and revealing the effectiveness of this MOF modification strategy. In fact, with the 10 wt% ZIF-8-umIm loading MMM, the highest value of CO₂/N₂ selectivity was 15.4 (12% higher than that of bare PIM-1) at a CO₂ permeability of 16 667 Barrer (52% higher than that of bare PIM-1). These findings highlight the promising potential of the ZIF-8 modification with umIm as a valuable filler material for MMMs in gas separation applications.