Hydrothermal stable ZIF-67 nanosheets via morphology regulation strategy to construct mixed-matrix membrane for gas separation

• Published in: Journal of membrane science 2020-01, Vol.593, p.117404, Article 117404
• Main Authors: Feng, Shou, Bu, Mengqi, Pang, Jia, Fan, Weidong, Fan, Lili, Zhao, Haoru, Yang, Ge, Guo, Hailing, Kong, Guodong, Sun, Haixiang, Kang, Zixi, Sun, Daofeng
• Format: Article
• Language: English
• Subjects: CO2 separation; Hydrothermal stable; Metal-organic frameworks; Mixed-matrix membranes; Oriented nanosheets
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2019.117404

Mixed matrix membranes (MMMs) based on metal-organic frameworks (MOFs) have proven to have high separation performance, which has great potential in separation applications. However, unsatisfactory hydrothermal stability is the Achilles' heel of MOFs in practical applications, which seriously hinders the development of MOF based MMMs. Under the advantage of crystal anisotropy, a morphology regulation strategy without post-treatment is presented for the first time to efficiently improve the stability of MOF fillers in aqueous solution. Contrary to the regular dodecahedron ZIF-67 crystals, the [211] oriented ZIF-67 nanosheets (NS) can maintain an ordered microporous framework integrally in the aqueous solution of membrane preparation. The exposed [211] crystal face exhibits enhanced stability due to a lower proportion of Co–N bond and higher surface atomic density. The flake morphology of ZIF-67 with economic incorporation (5.0 wt %) offers the MMMs significantly enhanced CO2 permeability of 139.4 barrer and CO2/N2 ideal selectivity of 73.2, improved by 50.7% and 76.0% compared with the pristine polymer membrane. This strategy provides a new idea for improving the hydrothermal stability of MOF materials and extends their separation applications under aqueous conditions. Oriented MOF nanosheets with higher hydrothermal stability than anisotropic crystals are applied to construct the mixed matrix membrane in aqueous solution, which exhibit highly improved CO2/N2 separation performance compared with the pristine polymer membrane. [Display omitted] •The hydrothermal stability of ZIF-67 is improved by morphology regulation.•The MMMs are fabricated with the low corporation of ZIF-67 in aqueous solution.•Significantly improved gas separation performance is achieved by the MMMs.