Aqueous Crystallization Strategy for Metastable h‐MoO3 Crystals with Polyvinylpyrrolidone Induction

Abstract Micro‐sized hexagonal‐phase MoO 3 ( h ‐MoO 3 ) crystals were successfully prepared by a polyvinylpyrrolidone (PVP) induced aqueous route with (NH 4 ) 6 Mo 7 O 24 · 4H 2 O and HCl as raw materials. The linear structure of the PVP molecules matches the tunnel structure of the metastable h ‐MoO 3 crystals and, thus, enables the induced crystallization in an aqueous solution even at near‐ambient temperatures (40–50 °C). The achieved h ‐MoO 3 crystals have good monodispersity with a one‐dimensional (1D) outline and hexagonal cross‐section. The H + /Mo ratio is another key factor for the synthesis of h ‐MoO 3 crystals. The photochromic properties of PVP‐dependent samples of h ‐MoO 3 crystals were studied under natural sunlight irradiation.