“…Since the discovery of graphene, two-dimensional (2D) layered materials such as metal chalcogenides, black phosphorus, transition metal oxides, and other 2D materials have raised great research interest due to their unique optical and electrical properties 1 – 5 . Among them, transition metal oxides possess numerous huge advantages, which can be prepared under oxygen atmosphere and endure high temperature 6 , 7 . As a typical case, layered K 4 Nb 6 O 17 (abbreviated as KN) has attracted considerable concern owing to its charming features and widespread applications in energy conversion, environmental purification, catalysis, non-linear optics, etc.…”