Humidity-responsive molecular gate-opening mechanism for gas separation in ultraselective nanocellulose/IL hybrid membranes. Issue 11 (14th May 2020)

• Record Type: Journal Article
• Authors: Janakiram, Saravanan; Ansaloni, Luca; Jin, Soo-Ah; Yu, Xinyi; Dai, Zhongde; Spontak, Richard J.; Deng, Liyuan
• Is Part Of: Green chemistry. Volume 22:Issue 11(2020)
• Page Start: 3546
• Page End: 3557
• Publication Date: 2020-05-14
• Subjects: Environmental chemistry -- Industrial applications -- Periodicals; Environmental management -- Periodicals; 660
• DOI: 10.1039/d0gc00544d
• Languages: English
• ISSNs: 1463-9262

Abstract

Abstract : A class of "green" hybrid membranes composed of nanocellulose and an ionic liquid exhibits exceptional separation properties arising from a humidity-responsive size-exclusive "gate" that allows selective CO2 permeation. Abstract : Nanofibrillated cellulose (NFC) represents an important class of bio-based nanomaterials that possess favorable properties including hydrophilicity, 1D structure, biodegradability, and surface tunability. Although widely known for its effective gas-barrier attributes due to its inherent crystallinity and hydrogen-bonding capability, the ability of NFC to form dense films has been of considerable interest in selective gas-separation applications as a viable replacement for synthetic polymers. With precise control of targeted properties at the nanoscale, NFC can likewise be used to enable selective removal of greenhouse gases such as CO2 . Herein we report a class of "green" hybrid membranes composed of NFC and an ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]), that together exhibit exceptional separation properties arising from controllable nanoscopic design. With this new class of green membranes, CO2 /N2 selectivities as high as ∼370 and CO2 permeabilities as high as ∼330 Barrer have been obtained at optimal IL loadings and/or humidity levels. The current work demonstrates that size exclusion of a molecular penetrant in a water-swollen NFC membrane matrix relies on the network architecture of partially swollen nanocellulose fibrils to selectively permeate CO2 through enhanced diffusive pathways. Additionally, the gas-transport and rheological properties of these NFC-fabricated membranes can be precisely tuned through the independent use of humidity as an external control parameter.