Millisecond lattice gasification for high-density CO₂- and O₂-sieving nanopores in single-layer graphene.

Abstract

Etching single-layer graphene to incorporate a high pore density with sub-angstrom precision in molecular differentiation is critical to realize the promising high-flux separation of similar-sized gas molecules, e.g., CO₂ from N₂ However, rapid etching kinetics needed to achieve the high pore density is challenging to control for such precision. Here, we report a millisecond carbon gasification chemistry incorporating high density (>10¹² cm^-2) of functional oxygen clusters that then evolve in CO₂-sieving vacancy defects under controlled and predictable gasification conditions. A statistical distribution of nanopore lattice isomers is observed, in good agreement with the theoretical solution to the isomer cataloging problem. The gasification technique is scalable, and a centimeter-scale membrane is demonstrated. Last, molecular cutoff could be adjusted by 0.1 Å by in situ expansion of the vacancy defects in an O₂ atmosphere. Large CO₂ and O₂ permeances (>10,000 and 1000 GPU, respectively) are demonstrated accompanying attractive CO₂/N₂ and O₂/N₂ selectivities.