Piezoelectric self-power supply driven by ferroelastic host–guest supramolecule with considerable electromechanical conversion capability

Crown ether supramolecules with host–guest structure bring the two most advanced application categories, namely information storage and energy conversion. The former was awarded the 2016 Nobel Prize in Chemistry, but the latter has thus far exhibited suboptimal electromechanical conversion properties. Enhancing the piezoelectric properties of such supramolecules has become a continuous and fascinating challenge. Here, we have made breakthrough progress in a crown ether-based ferroelastic supramolecular rotator [(N,N-dimethylethylenediammonium)(18-crown-6)]BF4 (MCBF) under the guidance of the crystallographic engineering. MCBF shows the record-high piezoelectric voltage coefficient (∼1000 × 10-3 V m N−1) and piezoelectric coefficient (∼46.1 pC N−1), which represent respectively improvements of 41.7% and 9.8% compared to the latest reported counterpart (J. Am. Chem. Soc. 145 (2023) 3187–3195). Notably, theoretical calculations elucidate that the ferroelasticity of MCBF contributes to its large piezoelectric response. In addition, an energy harvesting device is successfully achieved for the first time to evaluate its potential as a piezoelectric self-power supply, and LEDs are successfully lit by harvesting mechanical energy. This work takes an important step towards artificial supramolecular machines and arouses broad interest in self-powered flexible devices.