[C(NH 2 ) 3 ] 2 Zn(CO 3 ) 2 : A Guanidinium-Templated Ultraviolet Nonlinear Optical Material.

A novel guanidinium-templated ultraviolet (UV) nonlinear optical zinc carbonate crystal, [C(NH 2 ) 3 ] 2 Zn(CO 3 ) 2 (GZCO), has been synthesized in a closed system at low temperatures. GZCO crystallizing in the tetragonal noncentrosymmetric nonpolar space group, P 4 1 2 1 2 exhibits a three-dimensional anionic framework constructed by interconnected [Zn 6 C 6 O 32 ] 12-membered ring channels with inorganic CO 3 triangles and ZnO 4 tetrahedra. Notably, the anhydrous GZCO shows a very high thermal stability among guanidine-based hybrid NLO materials benefiting from the confinement effect of the organic cations within inorganic channels. The UV-visible transmittance spectrum reveals that GZCO has a short UV cutoff edge of 210 nm, corresponding to the large band gap of 5.9 eV. GZCO exhibits a mild second-harmonic generation efficiency of 0.5 × KH 2 PO 4 with type-I phase-matching behavior.