Chiral (R/S-MPz)Ge₄I₁₀ With Unique 2D [Ge₄I₁₀] Layered Structure and Large Chirality-Induced Nonlinear Optical Effect

Chiral organic-inorganic hybrid metal halides (OIMHs) with intrinsic non-centrosymmetric structures have attracted considerable attention for their potential nonlinear optical (NLO) applications. However, compared to their achiral counterparts, the chirality-induced mechanism underlying their NLO effects remains unclear. This study reports for the first time a pair of Ge-based chiral OIMHs (R/S-MPz)Ge₄I₁₀ with a unique 2D [Ge₄I₁₀]^2- layers, exhibiting a second-harmonic effect approximately five times greater than that of benchmark K₂HPO₄ (KDP). This represents the highest value achieved to date among reported chiral Ge-based OIMHs and far exceeds those observed in the organic R/S-MPz. First-principles calculations reveal that the unique [Ge₄I₁₀]^2- layer, constructed by edge-shared [GeI₆]^4- octahedra induced by chirality, is crucial for the dominate NLO effect. By further enhancing the polarity of the organic component, this material achieves a gain record of ∼15×KDP. Our study not only expands the family of chiral Ge-based OIMHs but also elucidates the relationship between chiral motif and NLO property, providing a rational design strategy for chiral NLO materials.