Bidirectional Size Control for Angstrom-Scale Graphene Pores by Competitive Growth and Etching

Precise control over angstrom-scale pores in graphene remains a central challenge for exploiting its potential for gas separation. Most pore formation methods produce broad pore-size distributions with a long tail of nanometer-scale, nonselective pores. Here, we present a strategy based on simultaneous competitive growth and etching during chemical vapor deposition. By coupling CH₄ as a carbon precursor with CO₂ as a mild etchant, we establish a continuous kinetic regime in which pore expansion and shrinkage emerge from the same growth environment and are tuned bidirectionally by gas-phase composition. Carbon isotope labeling reveals that pore shrinkage proceeds via edge-mediated lattice reconstruction fueled exclusively by CH₄, while CO₂ acts solely as an etchant. This competitive growth-etching interplay enables the systematic contraction of nanometer-scale pores into angstrom-scale apertures. The resulting porous graphene exhibits remarkably enhanced molecular sieving behavior, providing a general framework for postsynthetic control of defect dimensions in two-dimensional materials.