A Noncentrosymmetric Metal‐Free Borophosphate: Achieving a Large Birefringence and Excellent Stability by Covalent‐Linkage

作者：Hui‐Li Zhang, Dong‐Xue Jiao, Xiaofei Li, Chao He, Xi‐Ming Dong, Kai Huang, Jinhua Li, Xing‐Tao An, Qi Wei, Guo‐Ming Wang · 发表于：Small · 年份：2024 · DOI：10.1002/smll.202401464 · 被引用次数：27 · 研究领域：Crystal Structures and Properties、Nonlinear Optical Materials Research、Crystal structures of chemical compounds

Abstract Organic–inorganic hybrid linear and nonlinear optical (NLO) materials have received increasingly wide spread attention in recent years. Herein, the first hybrid noncentrosymmetric (NCS) borophosphate, (C 5 H 6 N) 2 B 2 O(HPO 4 ) 2 (4PBP), is rationally designed and synthesized by a covalent‐linkage strategy. 4‐pyridyl‐boronic acid (4 PB) is considered as a bifunctional unit, which may effectively improve the optical properties and stability of the resultant material. On the one hand, 4 PB units are covalently linked with PO 3 (OH) groups via strong B–O–P connections, which significantly enhances the thermal stability of 4PBP (decomposition at 321, vs lower 200 °C of most of hybrid materials). On the other hand, the planar π ‐conjugated C 5 H 6 N units and their uniform layered arrangements represent large structural anisotropy and hyperpolarizability, achieving the largest birefringence (0.156 @ 546 nm) in the reported borophosphates and a second‐harmonic generation response (0.7 × KDP). 4PBP also exhibits a wide transparency range (0.27–1.50 µm). This work not only provides a promising birefringent material, but also offers a practical covalent‐attachment strategy for the rational design of new high‐performance optical materials.