BN-backbone phenine nanotubes: A first-principles study of structure, porosity, and electronic tunability

Phenine-based nanostructures, recently proposed as porous analogs of carbon nanotubes and graphene, exhibit unique structural flexibility and electronic tunability. Extending this concept to boron–nitrogen (BN) analogs introduces additional opportunities due to the polar nature of B–N bonds and their known stability in hexagonal BN systems. In this work, we present, for the first time, a theoretical investigation of BN-substituted phenine nanotubes, focusing on the (6,6) and (6,0) configurations with varying hydrogen terminations. Inspired by the contrasting properties of graphene and hexagonal boron nitride, as well as carbon and BN nanotubes, we demonstrate that BN incorporation into phenine architectures leads to significant modifications in their physical behavior. Density functional theory calculations reveal that hydrogen removal leads to significant structural rearrangements, including anisotropic deformations and diameter variations up to 37% relative to the fully hydrogenated form. However, the tubular architecture of the BN substituted species are maintained. The analysis of bonding and charge density shows a transition from mixed single–double B–N bonds to more polarized distributions, where nitrogen dominates charge localization. Selective dehydrogenation induces distinct intra-ring charge transfers, reflecting the interplay between geometry and electronic structure. The band-gap values can be effectively tuned by selecting different chiralities and adjusting the degree of hydrogenation. The energy-band structures, projected density of states, the optical properties and the Raman spectra are analyzed based on the chirality and the hydrogenation of the BN-phenine nanotubes. These results demonstrate that BN substitution and hydrogen control provide efficient routes to tune the mechanical and electronic properties of phenine nanotubes, suggesting their potential for novel semiconducting and optoelectronic applications.