Maximizing the linear and nonlinear optical responses of alkaline tricyanomelaminate.

High-performance bi-functional materials are in urgent demand for the next-generation integrated optical devices. In this work, we successfully synthesized the first tricyanomelaminate with bi-functional optical responses, namely CsCN•HO (), from its analogue NaCN•3HO by a facile ion exchange method. In contrast to NaCN•3HO, realizes an optimal arrangement of -conjugated (CN) anion groups in its crystal structure. As a result, the second-order nonlinear optical (NLO) response is greatly enhanced from nearly zero of NaCN•3HO to ∼9.8 × KHPO of . Furthermore, exhibits a giant linear optical anisotropic response (i.e. birefringence) of 0.52 at the wavelength of 550 nm. Both responses are almost the largest among the inorganic compounds of -conjugated rings, which indicates that has great potential as a bi-functional optical crystal. Structural and theoretical analyses reveal the microscopic origin of excellent optical properties. This work would attract a lot of interest to the persistently neglected potential of tricyanomelaminates as linear optical and NLO crystals.