Energy and Distribution: A Frontier Orbital Landscape for BN-Embedded Polycyclic Aromatic Hydrocarbons

1,2-BN incorporation into polycyclic aromatic hydrocarbons (PAHs) provides a powerful strategy to modulate electronic structure while preserving the conjugated framework. However, a unified understanding from a frontier molecular orbital (FMO) perspective remains lacking, despite the central role of frontier orbitals in governing a wide range of molecular properties. Here, we present a conceptual framework to analyze BN-embedded PAHs based on two complementary descriptors: the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap and the spatial distribution of frontier orbitals. BN incorporation can either enlarge or narrow the HOMO-LUMO gap, thereby governing molecular stability and optical properties. Meanwhile, BN-induced orbital redistribution critically influences chemical reactivity and charge-transport behavior. By integrating energy and distribution, this framework rationalizes diverse experimental observations and provides guiding principles for the design of BN-embedded organic semiconductors.