Formation of a defect-free polyimide/zeolitic imidazolate framework-8 composite membrane for gas separation: in-depth analysis of organic–inorganic compatibility

BACKGROUND: The incompatibility between polymer matrix and filler usually leads to the formation of nonselective voids at the polymer/filler interface, which subsequently lowers the gas separation performance. In view of this, the effectiveness of (3-aminopropyl)triethoxysilane (APTES) in promoting the interaction between alumina and polyimide (PI), as well as PI and zeolitic imidazolate framework-8 (ZIF-8) during the synthesis of PI/ZIF-8 composite membrane was assessed experimentally. The experimental data also were verified through the calculation of binding energy via molecular simulation. RESULTS: It was found that APTES improved the adhesion between alumina-PI and allowed the formation of a defect-free alumina-supported PI membrane up to five layers of PI dip-coating. Similarly, the compatibility between PI–ZIF-8 also was shown to be improved by APTES. Indeed, the optimum CO₂ permeance and CO₂/N₂ selectivity were found at 93.47 GPU and 7.50, respectively, at five layers of ZIF-8 dip-coating. In this work, the polymer-filler compatibility also was verified through molecular simulation whereby a lower binding energy was obtained for system incorporated with APTES. CONCLUSION: In short, the results indicated that APTES was effective in stabilizing the PI/ZIF-8 composite membrane. The polymer-filler compatibility also was successfully evaluated through the simple molecular simulation approach without requiring time-consuming experiments.