Improved CO₂/CH₄ separation performance of mixed‐matrix membrane by adding ZIF‐7‐NH₂ nanocrystals

Abstract

Membrane‐based technology is an attractive alternative in terms of CO2 separation. Pebax‐based membranes are regarded as potential candidates for CO2 separation due to the favorable interaction between its poly (ethylene oxide) chains with CO2 molecules and inorganic fillers. However, the separation performance for CO2/CH4 mixture is still suffered from the moderate gas permeability and selectivity. To overcome this problem, in this work, amino‐functionalized zeolite imidazolate framework (ZIF‐7‐NH2) nanocrystals were used as fillers to blend with Pebax 1657 for fabricating mixed‐matrix membranes (MMMs). XRD, Brunauer–Emmett–Teller (BET), scanning electron microscope, and 1H nuclear magnetic resonance characterization indicated that ZIF‐7‐NH2 with the highest crystallinity was synthesized. Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and Young's modulus showed that it has good interfacial interaction. Gas separation test results showed that both the CO2 permeability and CO2/CH4 selectivity of the 31 wt% ZIF‐7‐NH2/Pebax MMMs increased by 80 and 170%, respectively. The improved performance is attributed to the addition of ZIF‐7‐NH2 nanocrystals and the favorable interfacial interactions between the polymer and ZIF‐7‐NH2 nanocrystals. Furthermore, the polyvinylidene fluoride supported hollow fiber composite membranes also exhibit the long‐term stability for CO2/CH4 separation.

CO2/N2 Gas Separation Using Pebax/ZIF-7—PSf Composite Membranes

“…P. Zhao et al [21] suggested that this gate-opening phenomenon may lead to an increase in CO 2 affinity due to the change in the electrostatic field brought about inside the particles. Several other studies [52,53] have shown that ZIF-7 has such high affinity while interacting with CO 2 that it causes the CO 2 solubility to increase. B.A.…”

Phase control of ZIF-7 nanoparticles via mechanochemical synthesis

“…This shows that mechanochemical synthesis has successfully opened a new route towards the formation of 100% amino functionalised ZIF-7 crystals (the highest reported loading of the amino group in ZIF-7 crystals synthesised via a mixed-linker strategy using the solvothermal route is 70%). 28,29 This indicates that mechanochemical synthesis can be a possible alternative route to form functionalised crystalline MOF particles not accessible via the normal solvothermal synthesis route. Further characterisation of these amino-functionalised particles can be found in S1d (ESI †).…”