Hierarchical flower-shaped NPB architectures are prepared via a facile solvent evaporation method and investigated by means of SEM, TEM, FT-IR, and XRD. The results indicate that each NPB flower is composed of a number of randomly oriented nanoflakes, which are single crystals and connect with each other. Furthermore, time-dependent experiments reveal that the NPB flowers are formed via a heterogeneous nucleation, coupled with “Ostwald ripening”. The densely packed films of NPB flowers, which can withstand extreme conditions, e.g., high temperature, strong acid, and strong alkali possess a durable water-repellent property.