Edge Reconstruction Drives Electronic and Catalytic Functions in Bilayer Iodinene

ABSTRACT Edges in 2D materials are central to emergent electronic and catalytic functionalities, yet their atomic structures in soft halogen‐based lattices remain poorly understood. Here, we resolve the edge motifs of bilayer iodinene through a global structure search based on particle swarm optimization and first‐principles calculations. Among various reconstructed zigzag edge configurations, we identify a zigzag edge (ZZ_5_I) that is both thermodynamically preferred and consistent with high‐resolution scanning transmission electron microscopy images. This reconstructed edge stabilizes through symmetric three‐ and fourfold iodine coordination, drives a semiconductor‐to‐metal transition, and exhibits nearly thermoneutral hydrogen adsorption free energy (ΔG H ≈ 0.07 eV), competitive with that of Pt(111). Edge reconstruction thereby provides structural and electronic tunability beyond the basal iodinene lattice, coupling stability, metallicity, and active‐site density. These results establish bilayer iodinene as a promising halogen‐based 2D catalyst and demonstrate the power of global structure prediction for uncovering functional edge reconstructions in deformable 2D lattices.