Rational Design of the Metal‐Free KBe2BO3F2⋅(KBBF) Family Member C(NH2)3SO3F with Ultraviolet Optical Nonlinearity

The first fluorosulfonic ultraviolet (UV) nonlinear optical (NLO) material, C(NH2 )3 SO3 F, is rationally designed by taking KBe2 BO3 F2 (KBBF) as the parent compound. C(NH2 )3 SO3 F features similar topological layers as KBBF by replacing inorganic (BO3 )3- with organic C(NH2 )3+ trigonal units and BeO3 F with SO3 F- tetrahedra. Therefore, C(NH2 )3 SO3 F is a metal-free UV NLO crystal. Benefiting from the coplanar configuration of the C(NH2 )3+ cationic groups, it possesses a large SHG response of 5×KDP and moderate birefringence of 0.133@1064 nm. Besides, it has a short UV cutoff edge of 200 nm. The calculated results reveal the shortest SHG phase-matching wavelengths can reach 200 nm. These findings highlight the exploration of metal-free compounds as nontoxic and low-cost UV NLO materials as a new research area.