Distortion-engineered C₁-symmetric inorganic molecular cages enable tunable chiroptical nonlinear optics with broad...

Chiroptical materials combining chirality with second-harmonic generation are attractive for polarization-resolved photonics, yet examples integrating strong chiroptical nonlinear activity, broad infrared transparency and inorganic robustness remain limited. Here we report a purely inorganic strategy in which molecular-level geometric distortion of intrinsically C₁-symmetric phosphorus-chalcogen cages tunes second-harmonic generation circular dichroism (SHG-CD). Site-selective homologous substitution yields enantiopure molecular cage crystals, S/R-P₄S₅, S/R-AsP₃S₅, S/R-P₄S₄Se and S/R-AsP₃S₄Se, spanning a controlled distortion series. These crystals exhibit pronounced SHG-CD, with ${\text{g}}_{\text{SHG}-\text{CD}}$  = 0.48-1.70 under 1064 nm excitation, strong SHG outputs of 1.1-2.8 × AgGaS₂ at 2050 nm, broad infrared transparency and high laser-induced damage thresholds. Across this series, SHG-CD correlates with distortion-driven molecular asymmetry, indicating that the cage dipole moment can serve as a practical descriptor for chiroptical nonlinear response within this isostructural molecular cage family. These results establish inorganic molecular cages as a tunable chiroptical nonlinear platform for infrared-transparent chiroptical nonlinear materials.