Record Enhancement of Curie Temperature in Host-Guest Inclusion Ferroelectrics.

Solid-state molecular rotor-type materials such as host-guest inclusion compounds are very desirable for the construction of molecular ferroelectrics. However, they usually have a low Curie temperature () and uniaxial nature, severely hindering their practical applications. Herein, by regulating the anion to control "momentum matching" in the crystal structure, we successfully designed a high-temperature multiaxial host-guest inclusion ferroelectric [(MeO-CH-NH)(18-crown-6)][TFSA] (MeO-CH-NH = 4-methoxyanilinium, TFSA = bis(trifluoromethanesulfonyl)ammonium) with the Aizu notation of F. Compared to the parent uniaxial ferroelectric [(MeO-CH-NH)(18-crown-6)][BF] with a of 127 K, the introduction of larger TFSA anions brings a lower crystal symmetry at room temperature and a higher energy barrier of molecular motions in phase transition, giving [(MeO-CH-NH)(18-crown-6)][TFSA] multiaxial ferroelectricity and a high up to 415 K (above that of BaTiO). To our knowledge, such a record temperature enhancement of 288 K makes its the highest among the reported crown-ether-based ferroelectrics, giving a wide working temperature range for applications in data storage, temperature sensing, actuation, and so on. This work will provide guidance and inspiration for designing high- host-guest inclusion ferroelectrics.