Fabrication of hydrophobic ZIFs based composite membrane with high CO_2 absorption performance

摘要

The membrane contactor has been considered an effective device to capture CO2, but its performance is limited by membrane wetting phenomena. In this work, the ZIF-8/ZIF-L (zeolitic imidazolate framework) based composite membrane with excellent hydrophobic stability and CO2 permeability was successfully fabricated by coating the dense layer on the porous PVDF (polyvinylidene fluoride) substrate. The dense layer was developed by evenly incorporating ZIF-8 nanocrystals and ZIF-L nanosheets into the polydimethylsiloxane (PDMS) polymer. The as-prepared membrane possessed competitive hydrophobicity with a water contact angle (WCA) of 131.8 degrees. And after a ten-day immersion test in CO2 absorbent, the WCA only declined by 9.8%, exhibiting excellent hydrophobic stability. Besides, the CO2 permeability of the composite membrane was 61.8x10(-8)center dot mol center dot m(-2)center dot s(-1)center dot Pa-1 with an ideal CO2/N-2 separation factor of similar to 20, which was effectively improved in comparison with the control membrane. In the CO2 absorption experiment, the prepared membrane achieved the competitive CO2 flux of 3.02x10(-3)center dot mol center dot m(-2)center dot s(-1) when the liquid velocity was 0.25 m center dot s(-1) and displayed robust long-term operating stability. Finally, the AC impedance technique was applied to continuously monitor the wetting state of composite membranes, which further investigated their anti-wetting ability.