Dialdehyde polyethylene glycol cross-linked poly(vinyl alcohol) membranes with enhanced CO2/N2 separation performance

The development of carbon dioxide (CO2) separation technology is crucial for mitigating global climate change and promoting sustainable development. In this study, we successfully synthesized an array of cross-linked poly(vinyl alcohol) (PVA) membranes, xALD-PEG-ALD-c-PVA, with enhanced CO2/N-2 separation performance by employing dialdehyde polyethylene glycol (ALD-PEG-ALD) as a cross-linker. The formation of the cross-linked network structure not only inhibits the crystallization of PVA but also disrupts hydrogen bonding and thus increases fractional free volume of PVA chains. Under the synergistic effect of these multiple factors, the cross-linked PVA membranes exhibit a significantly improved CO2 permeability. Moreover, they maintain high CO2/N-2 selectivity, attributing to the CO2-philic characteristic of ethylene oxide groups in the cross-linked structure. At the ALD-PEG-ALD content of 1.6 mmol g(-1), the xALD-PEG-ALD-c-PVA membrane demonstrates a CO2 permeability of 41.4 barrer and a CO2/N-2 selectivity of 57.4 at 2 bar and 25 degrees C. Furthermore, compared with the pristine PVA membrane, xALD-PEG-ALD-c-PVA membranes manifest superior mechanical properties and outstanding separation performance for a CO2/N-2 (15/85, vol%) gas mixture. The excellent combination of permeability and selectivity makes xALD-PEG-ALD-c-PVA membranes highly promising for various CO2 separation applications.