Copper boride monolayers: unprecedented low-dimensional boron networks beyond borophene

Interweaving boron with metal atoms within a two-dimensional plane represents a promising strategy to fabricate unconventional boron networks. However, the practical synthesis and structural determination of such materials remain significantly challenging. Recent experimental realizations of epitaxial copper borides have pioneered the exploration of these unique boron networks. Here, we provide a comprehensive review of these advances, focusing on the structural resolution of the Cu8B14 phase on Cu(111)—originally debated as borophene—and the predicted Cu7B15 phase, alongside the recently realized metalloborophene CuB4. Finally, we outline future directions for extending this boride family and exploring their potential in superconductivity and catalysis.