Discovering Pseudo-Supertetrahedral Functional Units in Salt-Inclusion Nonlinear Optical Material [Ba₂₂(SO₄)₅][Zn₁₄Ga₁₈S₅₈]

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Chalcogenide supertetrahedral functional units play a vital role in both fundamental research and technological applications, but discovering new types of these units remains a significant challenge. This gap is largely due to the difficulty in inducing stable, novel supertetrahedral structures with unique properties. In this work, we successfully synthesize [Ba22(SO4)5][Zn14Ga18S58] (BZGSO), the first sulfate-incorporated salt-inclusion chalcogenide, using high-temperature solid-state methods. BZGSO features a unique, noncentrosymmetric FTW-type framework composed of unprecedented pseudosupertetrahedral [Zn13Ga16S58] functional units. These units are formed by defective [Zn3Ga4S16] clusters around a [ZnS6] octahedron. Notably, BZGSO exhibits promising characteristics for infrared nonlinear optical applications. The theoretical analysis reveals key structure–property relationships, and a systematic study of X/Zn/Ga/S compounds suggests a trend in structural dimensionality based on [X/(Zn+Ga)] ratios. This work not only advances the understanding of supertetrahedral chemistry but also paves the way for the discovery of materials with potential technological applications.