Bandgap Tunable Oxynitride LaNb ₂ O _7–x N _x Nanosheets

Abstract Bandgap tunable lanthanum niobium oxynitride [LaNb 2 O 7‐x N x ] (1+x)− nanosheet is prepared by the delamination of a Ruddlesden−Popper phase perovskite oxynitride via ion−exchange and two−step intercalation processes. The lanthanum niobium oxynitride nanosheets have a homogeneous thickness of 1.6 nm and exhibit a variety of chromatic colors depending on the nitridation temperature of the parent‐layered oxynitride. The bandgap energy of the nanosheets is determined by ultraviolet photoemission spectroscopy, Mott–Schottky, and photoelectrochemical measurements and is found to be tunable in the range of 2.03–2.63 eV. Furthermore, the oxide/oxynitride superlattice structures are fabricated by face−to−face stacking of 2D crystals using oxynitride [LaNb 2 O 7‐x N x ] (1+x)− and oxide [Ca 2 Nb 3 O 10 ] − nanosheets as building blocks. Moreover, the superlattices‐like restacked oxynitride/oxide nanosheets hybrid exhibits unique proton conductivity and dielectric properties strongly influenced by the oxynitride nanosheets and enhanced photocatalytic activity under visible light irradiation.