Synthetic methodology is considered a holy grail in both organic chemistry and materials science. Over the past few decades, researchers have explored graphene‐type molecules (or nanographenes) through classic Scholl oxidative cyclodehydrogenation. Despite the successes achieved with various nanographenes, the development of new methods to synthesize these highly desired molecules lags behind. Herein, we developed a facile and effective method to produce a series of nanographenes bearing nitrogen (N)‐doped pentagon‐heptagon pairs in acceptable yields. Modification of the heptagonal ring endowed the resultant nanographenes with tunable physicochemical properties; for instance, M9 exhibited both aggregation‐caused quenching and aggregation‐induced emission behavior. Most strikingly, novel nanographenes containing N‐doped pentagon‐octagon pairs were also obtained using the same synthetic strategy, demonstrating the superior versatility and efficiency of the proposed ring expansion method.

Pentagon–heptagon embedded polycyclic aromatic hydrocarbons (PAHs) have aroused increasing attention in recent years due to their unique physicochemical properties. Here, for the first time, this report demonstrates a facile method for the synthesis of a novel B2N2‐doped PAH (BN‐2) containing two pairs of pentagonal and heptagonal rings in only two steps. In the solid state of BN‐2, two different conformations, including saddle‐shaped and up‐down geometries, are observed. Through a combined spectroscopic and calculation study, the excited‐state dynamics of BN‐2 is well‐investigated in this current work. The resultant pentagon–heptagon embedded B2N2‐doped BN‐2 displays both prompt fluorescence and long‐lived delayed fluorescence components at room temperature, with the triplet excited‐state lifetime in the microsecond time region (τ = 19 µs). The triplet−triplet annihilation is assigned as the mechanism for the observed long‐lived delayed fluorescence. Computational analyses attributed this observation to the small energy separation between the singlet and triplet excited states, facilitating the intersystem crossing (ISC) process which is further validated by the ultrafast spectroscopic measurements.