2D chiral organic salts with a large piezoelectric response.

The piezoelectric effect, essential for sensing and energy harvesting, has driven the search for high-performance materials beyond toxic ceramics and low-output polymers. In recent years, chiral molecular crystals have emerged as promising candidates due to their structural tunability and solution processability. However, their piezoelectric coefficients typically remain below 10 pC N-1, limited by weak or poorly aligned molecular dipoles. Here, we show that chiral 4-bromo α-methylbenzylammonium chloride (R/S-4-BrPEAC) forms large single crystals via simple evaporation. The structure comprises a compliant 2D hydrogen-bonded network in which cations with large intrinsic dipoles align uniformly along the b-axis. This ordered packing enables efficient dipole reorientation under stress, yielding a high piezoelectric coefficient of 49 pC N-1, which ranks among the best reported for chiral molecular piezoelectrics. This work highlights simple, metal-free chiral organic salts as high-performance piezoelectric materials for flexible and biocompatible electromechanical applications.