A density functional theory (DFT) investigation has been performed in this work on the cage-like boron-rich boron oxide clusters B n (BO) n 2− , CBn−1(BO) n − , and C2Bn−2(BO) n (n = 5−12) which are boronyl analogues of the closo-boranes B n H n 2− , monocarboranes CBn−1H n − , and dicarboranes C2Bn−2H n . These boron oxide clusters possess similar geometrical and electronic structures with the corresponding boranes and carboranes and prove to be three-dimensional (3D) aromatic compounds, consistent with the previously proposed BO/H isolobal analogy. Neutral C2Bn−2(BO) n species possess considerably high ionization potentials in the range 12.0–12.7 eV and CBn−1H n − monoanions have the vertical electron detachment energies in the range 6.6–9.4 eV at the DFT level. BO terminals singly bonded to the skeletal vertexes through a B atom possess the characteristic stretching vibrational frequencies at about 2000 cm−1, clearly indicating the existence of B ≡ O triple bonds in these clusters. Experimental syntheses and characterizations of these interesting clusters may expand the structural concepts of boron oxides and bring important applications for boron oxide clusters as molecular devices in chemistry and new materials in boron neutron capture therapy.