Li[LiCs₂ Cl][Ga₃ S₆ ]: A Nanoporous Framework of GaS₄ Tetrahedra with Excellent Nonlinear Optical Performance

A large nonlinear optical (NLO) coefficient and a wide band gap are two crucial but contradictory parameters that are difficult to achieve simultaneously in a single infrared (IR) NLO compound. A salt-inclusion chalcogenide (SIC), Li[LiCs₂ Cl][Ga₃ S₆ ] (1), was prepared that presents a nanosized tunnel framework constructed from monotype chalcogenide tetrahedra. Highly oriented covalent GaS₄ tetrahedra in the host lead to a moderate second harmonic generation response (0.7 AgGaS₂ ), and ionic guests effectively broaden the band gap to the widest value (4.18 eV) among all IR NLO chalcogenides, thereby achieving a remarkable balance between NLO efficiency and band gap.