Chemical Substitution‐Driven Design of a High‐Performance Noncentrosymmetric Bismuth Molybdenum Selenite

Abstract The hydrothermal synthesis and characterization of a novel bismuth molybdenum selenite material, Bi₂F₂(MoO₃)₂(SeO₃)₂·H₂O, designed using a chemical substitution‐based approach, is reported. This material represents the first example of its kind in the Bi–Mo–Se system, providing new insights into noncentrosymmetric (NCS) crystal engineering. The compound exhibits outstanding nonlinear optical (NLO) properties, including a second‐harmonic generation (SHG) efficiency 1.2 times that of KTiOPO₄ and a birefringence of 0.118 at 546.1 nm. Additionally, it demonstrates a wide transparency range (0.36–10 µm), making it a promising candidate for advanced NLO applications. Structural and computational analyses show that the remarkable SHG response is driven by the highly distorted MoO₆ octahedra, strong interatomic interactions within 1D chains, and the highly polarizable Bi³⁺ and SeO₃ groups. Furthermore, the compound is thermally stable after dehydration and exhibits a strong affinity for occupying its void space within the 5‐membered ring (5‐MR). These findings open new avenues for the design of NCS materials with enhanced optical functionalities, offering significant potential in the development of advanced solid‐state materials.