ZIF-8 nanoparticles with tunable size for enhanced CO2 capture of Pebax based MMMs

• Published in: Separation and purification technology Vol. 214; pp. 111 - 119
• Main Authors: Zheng, Wenji, Ding, Rui, Yang, Kai, Dai, Yan, Yan, Xiaoming, He, Gaohong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2019
• Subjects: CO2 capture; Mixed matrix membranes; Pebax; Size-tunable ZIF-8; Pebax; CO2 capture; Size-tunable ZIF-8; Mixed matrix membranes
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2018.04.010

•Size-tunable ZIF-8 nanoparticles were distributed uniformly in Pebax without obvious defects.•ZIF-8 nanoparticles with different sizes were obtained in microemulsion by controlling the ratio of Zn2+ to Hmim.•Both CO2 permeability and CO2/N2 selectivity are improved significantly by incorporation of ZIF-8. Poly (ether-block-amide) (Pebax) based mixed matrix membranes (MMMs) were prepared by using size-tunable ZIF-8 nanoparticles as fillers. ZIF-8 nanoparticles with sizes of 40, 60, 90 and 110 nm (ZIF-8-40, ZIF-8-60, ZIF-8-90 and ZIF-8-110) were synthesized in microemulsion by controlling the ratio of Zn2+ to Hmim (1:16, 1:8, 1:5, 1:2). And they were distributed uniformly in Pebax matrix without obvious agglomerations and defects at the loading of 0–20 wt.%, which was confirmed by field-emission scanning electron microscopy (FE-SEM). The incorporation of ZIF-8 resulted in a significant improvement in CO2 permeability and the CO2/N2 selectivity increased with the BET surface area of ZIF-8 increasing. The enhanced permeability is attributed to an improvement in the free volume of the polymer induced by larger sized ZIF-8, while the increased selectivity results from the high specific surface area of large sized ZIF-8, which can provide more active sites for CO2 capture and great mass transfer resistance for N2. At 5 wt.% loading of ZIF-8-90, the MMM presents the best separation performance with CO2 permeability of 99.7 Barrer and CO2/N2 selectivity of 59.6, both of which are increased by about 25% by comparison to the pure Pebax membrane. The present study provides an effective way to obtain size-controlled ZIF-8 fillers and high separation performances of Pebax based MMMs.