Pressure‐Assisted Dimensional Transformation of 2D Hydrogenated Borophene into 0D Boron Quantum Dots

ABSTRACT Borophene is a monoelemental two‐dimensional (2D) material whose electron‐deficient bonding renders free‐standing monolayers intrinsically unstable, raising the question of how borophene can be converted into stable boron nanostructures. Borophene's structural stability and electronic properties are strongly influenced by vacancy configurations and defect engineering, while hydrogenation offers an additional pathway for stabilization and property tuning. Here, we introduce a solvent‐free solid‐state route that transforms hydrogenated borophene (HB) into either B 2 O 3 nanoplatelets or boron quantum dots (BQDs) via thermal dehydrogenation. Cleavage of B─H bonds releases hydrogen gas, whose escape under flowing N 2 facilitates structural reconstruction and leads to the formation of B 2 O 3 nanoplatelets. In sealed conditions, hydrogen accumulation generates internal pressure that drives fragmentation of the boron framework into BQDs. The resulting materials exhibit distinct photoluminescence (PL) behavior that correlates with their structural evolution, in agreement with first‐principles calculations of band‐gap changes. This work establishes solvent‐free, pressure‐assisted dimensional engineering of boron nanostructures and provides a new strategy for controlling the structural and optoelectronic properties of boron‐based materials.