Bottom-up approaches to form superatom-assembled 2D few-layered borophanes and carborophanes and 3D α-B₁₂, γ-B₂₈, and B₄C based on icosahedral B₁₂ and CB₁₁

Using the experimentally known aromatic icosahedral I_h B₁₂H₁₂²⁻ and C_5v B₁₁CH₁₂⁻ as building blocks and based on extensive density functional theory calculations, we present herein bottom-up approaches to form the superatom-assembled two-dimensional (2D) few-layered α-rhombohedral borophanes (B₁₂)_nH₆ (α-1–5) and (B₁₂)_nH₂ (α-6–10), γ-orthorhombic borophanes (B₁₂-B₂)_nH₈ (γ-1–5), and carborophanes (CB₁₁-CBC)_nH₈ (σ-1–5) (n = 1–5) and experimentally known three-dimensional (3D) α-B₁₂, γ-B₂₈, and B₄C crystals based on aromatic icosahedral B₁₂ and CB₁₁, with the B–B dumbbells in γ-1–5 and C–B–C chains in σ-1–5 serving as interstitial units to help stabilize the systems. As both chemically and mechanically stable species, the optimized 2D monolayer, bilayer, trilayer, tetralayer, and pentalayer borophanes and carborophanes all turn out to be semiconductors in nature, in particular, the few-layered carborophanes σ-3–5 ((CB₁₁-CBC)_nH₈ (n = 3–5)) with the calculated band gaps of E_gap = 1.32–1.26 eV appear to be well compatible with traditional silicon semiconductors in band gaps. Detailed adaptive natural density partitioning (AdNDP) bonding analyses indicate that both the icosahedral B₁₂ and CB₁₁ cages in these 2D and 3D crystal structures follow the universal superatomic electronic configuration of 1S²1P⁶1D¹⁰1F⁸ matching the n + 1 Wade’s rule (n = 12), rendering local spherical aromaticity and overall high stability to the systems.