Graphene oxide-melamine nanofilm composite membrane for efficient CO₂ gas separation

Technologies that absorb CO₂ are essential for meeting the world's carbon–neutral and carbon-negative goals. When compared to the traditional adsorption/absorption processes, membrane separation is more energy-efficient. Graphene oxide (GO) membrane is one such kind of membranes that is anticipated to provide a solution for separating CO₂ gas. The repulsive forces between carboxyl groups on GO nanosheets in GO membranes typically result in excessively high interlayer distance and poor performance for fine molecule separations such as gas separation. The GO interlayer channels can be effectively tuned by adding new binders/crosslinkers to enhance their size-discriminating capabilities. Here, we introduce melamine, a small molecule, for the first time into the GO layer, where it reacts with oxygen-containing groups to enrich the amine functional group, which aims to facilitate CO₂ transport. With a CO₂ permeance of 68.02 Barrer and a CO₂/N₂ ideal selectivity of 37.75, which is double that of pure GO, the produced ultrathin GO-melamine membrane (∼0.5 μm) demonstrated good gas separation capability. Throughout the continuous separation tests of mixed gases, the membrane retains its structural and performance stability.