Enabling Energy Harvesting and Underwater Ultrasound Detection with Chiral <scp>0D</scp> Hybrid Tin Bromides ^†

Comprehensive Summary Chiral hybrid metal halides (HMHs) are gaining significant attention as next‐generation materials for piezoelectric energy harvesting and underwater ultrasound sensing, owing to their facile synthesis, structural tunability, and inherently low acoustic impedance. However, most chiral halide crystals lack longitudinal piezoelectricity due to centrosymmetric space group limitations, while low‐dimensional chiral analogs with reduced elastic moduli remain insufficiently investigated. Herein, we report two chiral zero‐dimensional HMHs compounds— R ‐(4MeOPEA) 2 SnBr 6 and S ‐(4MeOPEA) 2 SnBr 6 (4MeOPEA = 4‐methoxy‐ α ‐methylbenzylammonium), that simultaneously exhibit remarkable longitudinal and shear piezoelectric responses. When embedded into polydimethylsiloxane (PDMS) composite matrices, these materials demonstrate high‐efficiency mechanical to electrical energy conversion and robust performance in underwater acoustic detection. Notably, the dual‐mode piezoelectric behavior, coupled with their intrinsically low acoustic impedance, eliminates the need for external impedance‐matching layers while preserving elevated ultrasonic sensitivity. This work establishes a new paradigm for designing high‐performance piezoelectric materials within HMH frameworks and broadens the scope for their deployment in advanced sensing and energy‐harvesting technologies.