Origin of CO2-philic Sorption by Graphene Oxide Layered Nanosheets and Their Derivatives

Graphene oxide (GO) is a promising 2D material for adsorbents and membranes, in particular, for the CO2 separation process. However, CO2 diffusion and sorption in GO and its layered structures are still not well understood because of its heterogeneous structure. Here we report CO2 sorption in GO and its derivatives (e.g., reduced GO (rGO)) in powders and films. These CO2 sorption behaviors reveal that GO is highly CO2-philic via complex CO2-functional-group-surface interactions, as compared with graphite and rGOs. Even in highly interlocked, lamellar GO films, CO2 molecules above a certain threshold pressure can diffuse into GO interlayers, causing GO films to swell and leading to dramatic increases in CO2 sorption. Intercalated water in GO interlayers can be removed by preferential CO2 sorption without any changes in the GO chemical structure. This finding helps to explain the origin of CO2 affinity with GO and has implications for preparing anhydrous GO assemblies for various applications.