On the CO₂ Harvesting from N₂ Using Grazyne Membranes

The separation of carbon dioxide (CO₂) from nitrogen (N₂) is at the core of any global warming remediation technology aimed at reducing the CO₂ content in the atmosphere. Chemical membranes designed to differentially permeate both molecules have become quite appealing due to their simple use, although many membrane-based separations stand out as a promising solution for CO₂ separation. These are environmentally friendly, with high active surface areas, compact design, easy to maintain and cost-effective, although the field is still growing due to the difficulties in the CO₂/N₂ separation. The present study poses grazynes, two-dimensional C-based materials with sp and sp² C atoms, aligned along stripes, as suited membranes for the CO₂/N₂ separation. The combination of density functional theory (DFT) and molecular dynamics (MD) simulations allow tackling the energetics, kinetics, and dynamics of the membrane effectiveness of grazynes with engineered pores for such a separation in a holistic fashion. The explored grazynes are capable of physisorbing CO₂ and N₂, thus avoiding material poisoning by molecular decoration, while the diffusion of CO₂ through the pores is found to be rapid, yet easier than that of N₂, in the rate order of the s^-1 in the 100-500 K temperature range. In particular, low-temperature CO₂ separation even for CO₂ contents below 0.5 % are found for [1],[2]{2}-grazyne when controlling the membrane exposure contact to the gas mixture, paving the way for exploring and using grazynes for air CO₂ remediation.