Facilitated Transport of CO2 Through the Transparent and Flexible Cellulose Membrane Promoted by Fixed-Site Carrier.

Facilitated transport cellulose membranes with different zinc ion loadings are fabricated via a facile and green solvent system (zinc chloride/calcium chloride solution). Zn2+ ions lower the pristine hydrogen bonds that normally reinforce the cellulose chains, and Ca2+ ions facilitate interactions among the Zn-cellulose chains to form nanofibrils. The strategy provides an effective route to immobilize zinc species into membrane matrix and constructs facilitated transport pathway for CO2 molecules. The self-standing membranes are transparent, flexible and demonstrate ultraselective CO2 permeation. The optimum separation performance is achieved over CM-0 with the highest zinc content (22.2%), and it exhibits a CO2 permeability of 155.0 Barrer, with selectivity ratios of 27.2 (CO2/N2) and 100.6 (CO2/O2). The excellent separation performance is assigned to the π complexation mechanism between Zn2+ and CO2.