Liquid-Metal Interfacial Chemistry for Crystal and Defect Engineering in Two-Dimensional Post-Transition-Metal Materials.

Liquid-metal-derived 2D materials have emerged as a versatile class of ultrathin systems enabled by dynamic and chemically active liquid metal interfaces. The atomically smooth, self-limiting surface layers formed at these interfaces provide unique pathways for the synthesis and transfer of ultrathin post-transition metal materials, supporting applications in optoelectronics, sensing, energy, and catalysis. However, material formation at liquid metal interfaces is governed by complex interfacial chemistry involving redox reactions, alloy thermodynamics, atomic migration, reactive atmospheres, and processing conditions. These processes directly influence crystal formation, phase, stoichiometry, and the generation of point, planar, and morphological defects. Here, we review how liquid metal interfaces control crystal and defect formation in 2D materials, highlighting key factors that influence defect formation, including atmospheric conditions, alloy composition, doping, and post-processing. We also discuss how these defects influence their electronic, optical, sensing, and piezoelectric properties. By reframing defects as tunable design parameters rather than unavoidable limitations, this Review establishes liquid metal interfacial chemistry as a powerful framework for engineering functional 2D materials with tailored properties and improved technological performance.