Facilitated Transport of CO 2 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). Zn 2+ ions lower the pristine hydrogen bonds that normally reinforce the cellulose chains, and Ca 2+ 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 CO 2 molecules. The self-standing membranes are transparent, flexible and demonstrate ultraselective CO 2 permeation. The optimum separation performance is achieved over CM-0 with the highest zinc content (22.2%), and it exhibits a CO 2 permeability of 155.0 Barrer, with selectivity ratios of 27.2 (CO 2 /N 2 ) and 100.6 (CO 2 /O 2 ). The excellent separation performance is assigned to the π complexation mechanism between Zn 2+ and CO 2 .