Using the experimentally known aromatic icosahedral superatoms I_h B₁₂H₁₂²⁻ and D_5d 1,12-C₂B₁₀H₁₂ as building blocks and based on extensive density functional theory calculations, we predict herein a series of core–shell superpolyhedral boranes and carboranes in a bottom-up approach, including the high-symmetry T_h B₁₂@B₁₅₂H₇₂²⁻ (2), C_2h C₂B₁₀@B₁₅₂H₇₂ (3), D_3d B₁₂@B₁₄₄H₆₆ (4), I_h B₁₂@C₂₄B₁₂₀H₇₂²⁻ (6), and D_5d C₂B₁₀@C₂₄B₁₂₀H₇₂ (7). More interestingly, the superatom-assembled linear D_2h B₃₆H₃₂²⁻ (8), close-packed planar D_3d B₈₄H₆₀²⁻ (10), and nearly close-packed core−shell D_3d B₁₂@B₁₄₄H₆₆ (4) can be extended periodically to form the one-dimensional (1D) α-rhombohedral borane nanowire B₁₂H₁₀ (Pmmm) (9), two-dimensional (2D) α-rhombohedral monolayer borophane B₁₂H₆ (P $\overline{3}$m1) (11), and the experimentally known three-dimensional (3D) α-rhombohedral boron (R $\overline{3}$m) (12) which can be viewed as an assembly of the monolayer B₁₂H₆ (11) staggered in vertical direction, setting up a bottom-up strategy to form low-dimensional boron-based nanomaterials from their borane “seeds” via partial or complete dehydrogenations. Detailed bonding analyses indicate that the high stability of these nanostructures originates from the spherical aromaticity of their icosahedral B₁₂ or C₂B₁₀ structural units which possess the universal skeleton electronic configuration of 1S²1P⁶1D¹⁰1F⁸ following the Wade’s n+1 rule. The infrared (IR) and Raman spectra of the most-concerned neutral B₁₂@B₁₄₄H₆₆ (4) and C₂B₁₀@C₂₄B₁₂₀H₇₂ (7) are computationally simulated to facilitate their experimental characterizations.

Supported bilayer α-borophene (BL-α borophene) on Ag(111) substrate has been synthesized in recent experiments. Based on the experimentally observed quasi-planar C_6v B₃₆ (1), its monolayer assembly α⁺-borophene B₁₁ (P6/mmm) (2), and extensive global minimum searches augmented with density functional theory calculations, we predict herein freestanding BL-α⁺ borophenes B₂₂ (Cmmm) (3) and B₂₂ (C2/m) (4) which, as the most stable BL borophenes reported to date, are composed of interwoven boron triple chains as boron analogs of monolayer graphene (5) consisting of interwoven carbon single chains. The nearly degenerate eclipsed B₂₂ (3) and staggered B₂₂ (4) with the hexagonal hole density of η = 1/12 and interlayer bonding density of u = 1/4 appear to be two-dimensional semiconductors with the indirect band gaps of 0.952 and 1.144 eV, respectively. Detailed bonding analyses reveal one delocalized 12c-2e π bond over each hexagonal hole in both the B₂₂ (3) and B₂₂ (4), similar to the situation in monolayer graphene which contains one delocalized 6c-2e π bond over each C₆ hexagon. Furthermore, these BL-α⁺ borophenes appear to remain highly stable on Ag(111) substrate, presenting the possibility to form supported BL-α⁺ borophenes.