Wu, ChaoJiang, XingxingWang, ZujianLin, LinLin, ZheshuaiHuang, ZhipengLong, XifaHumphrey, MarkZhang, Chi2022-10-171433-7851http://hdl.handle.net/1885/275547Birefringence is a fundamental optical property for linear and nonlinear optical (NLO) materials. Thus far, it has proved to be very difficult to engineer large birefringence in optical crystals functioning in the UV region. Herein, we report the first 2D rare-earth iodate-nitrate crystal Sc(IO3)2(NO3) (SINO), which is shown to exhibit giant optical anisotropy. Air-stable SINO possesses a short UV absorption edge (298 nm), a strong NLO response (4.0 times that of benchmark KH2PO4) for the nitrate family, and the largest birefringence (Δn=0.348 at 546 nm) of inorganic oxide optical crystals. The unusually large birefringence and NLO response can be attributed to an optimized 2D layered structure, combined with highly polarizable and anisotropic building units [IO3]− and [NO3]−. These findings will facilitate the development of UV linear and NLO materials with giant optical anisotropy and promote their potential application in optoelectronic devices.This research was financially supported by the NationalNatural Science Foundation of China (no. 51432006), theMinistry of Education of China for the Changjiang Innova-tion Research Team (no. IRT14R23), the Ministry of Educa-tion and the State Administration of Foreign Experts Affairsfor the 111 Project (no. B13025), and the Innovation Programof Shanghai Municipal Education Commission. C.W. thanksthe National and Shanghai Postdoctoral Program for Inno-vative Talents (nos. BX201800216 and 2018192). M.G.H.thanks the Australian Research Council for support(DP170100411)application/pdfen-AU© 2020 Wiley-VCH GmbH202110.1002/anie.2020124562021-11-28