Multipulsed Millisecond Ozone Gasification for Predictable Tuning of Nucleation and Nucleation-Decoupled Nanopore Expansion in Graphene for Carbon Capture

Predictable and tunable etching of angstrom-scale nanopores in single-layer graphene (SLG) can allow one to realize high-performance gas separation even from similar-sized molecules. We advance toward this goal by developing two etching regimes for SLG where the incorporation of angstrom-scale vacancy defects can be controlled. We screen several exposure profiles for the etchant, controlled by a multipulse millisecond treatment, using a mathematical model predicting the nucleation and pore expansion rates. The screened profiles yield a narrow pore-size-distribution (PSD) with a majority of defects smaller than missing 16 carbon atoms, suitable for CO₂/N₂ separation, attributing to the reduced pore expansion rate at a high pore density. Resulting nanoporous SLG (N-SLG) membranes yield attractive CO₂ permeance of 4400 ± 2070 GPU and CO₂/N₂ selectivity of 33.4 ± 7.9. In the second etching regime, by limiting the supply of the etchant, the nanopores are allowed to expand while suppressing the nucleation events. Extremely attractive carbon capture performance marked with CO₂ permeance of 8730 GPU, and CO₂/N₂ selectivity of 33.4 is obtained when CO₂-selective polymeric chains are functionalized on the expanded nanopores. We show that the etching strategy is uniform and scalable by successfully fabricating high-performance centimeter-scale membrane.