Enhanced Nonlinear Optical Response and Self‐Powered CPL Detection in Unique Triangular–Tetrahedral Chiral Copper(I) Halides

Abstract The low‐coordination polyhedral architecture of Cu(I)‐based chiral metal halides induces significant structural distortions, endowing these materials with remarkable circularly polarized light (CPL) activity and exceptional nonlinear optical (NLO) performance. However, achieving highly selective CPL detection with large dissymmetry factors ( g lum ) in Cu(I)‐based chiral metal halides remains a significant challenge. Herein, we prepared 1D chiral ( R / S )‐MPZCu 2 Cl 4 (where MPZ is 2‐methylpiperazine) halides with the unique triangular–tetrahedral configuration in the noncentrosymmetric cubic P 1 2 11 space group, resulting in substantial structural distortions, which significantly impact nonlinear susceptibility. Consequently, ( R )‐MPZCu 2 Cl 4 halide exhibits efficient second harmonic generation (SHG), which is 7.29 times as high as that of KH 2 PO 4 . Additionally, ( R )‐MPZCu 2 Cl 4 halide also exhibits remarkable third harmonic generation (THG) response, and g THG‐CD is as high as +0.309, which is the first demonstration of THG‐based CPL detection in Cu(I)‐based metal halides. The self‐powered CPL photodetectors based on ( R / S )‐MPZCu 2 Cl 4 show high CPL distinguishability at 0 V and further achieve self‐powered X‐ray detection with excellent low‐dose detection and radiation resistance. Our study provides valuable insights into the structure–performance relationship in chiral organic–inorganic hybrid Cu(I) halides, paving the way for next‐generation multifunctional optoelectronic devices.