Scalable metallurgical route for top-down production of amorphous two-dimensional boron nanosheets

The development of boron-based two-dimensional materials has been constrained by the absence of scalable synthesis routes producing processable material beyond substrate-bound epitaxial films. Here we demonstrate a scalable top-down strategy for producing layered boron nanosheets from bulk crystalline boron. Our approach exploits a metallurgically derived Li x B 1-x alloy, which undergoes controlled chemical delithiation followed by liquid-phase exfoliation to yield amorphous layered boron nanosheets as a readily dispersible powder compatible with solution processing. Structural and chemical characterization demonstrates the conversion of bulk crystalline boron into a layered, amorphous nanosheet material with micrometer-scale lateral dimensions. These nanosheets can be assembled into continuous films by spray coating, enabling systematic investigation of thickness-dependent optical properties and the fabrication of stable coatings with high solar absorptivity for concentrated solar power applications. This work establishes a metallurgical pathway to processable B/O-rich boron nanosheets, providing a scalable pathway toward processable boron-based layered nanomaterials and expanding opportunities for their integration into energy and photonic technologies.