Recent advances in non-π-conjugated nonlinear optical sulfates with deep-UV absorption edge

Deep-ultraviolet (deep-UV) nonlinear optical (NLO) crystals are of current interest because they play an indispensable role in modern scientific equipment. Searching these crystals was traditionally limited to π-conjugated systems, such as borates and carbonates. In 2019, our group reported two non-π-conjugated sulfates as new sources of deep-UV NLO crystals for the first time. In this mini review, we provide a comprehensive overview of the recent development of non-π-conjugated NLO sulfates with deep-UV absorption edge in aspect of synthesis methods, crystal structures, thermal stability, and optical performance. Besides, we conclude the crucial structure-property relationships, and further give some prospects for exploring non-π-conjugated NLO sulfates with deep-UV absorption edge with high thermal stability, enhanced second-order NLO effects, birefringence, etc. We believe that this mini review will not only facilitate researchers to design superior non-π-conjugated NLO sulfates with deep-UV absorption edge but also shed useful insights on the explorations of other non-π-conjugated deep-UV NLO crystal systems.