ABX3-type perovskites and metal–organic frameworks (MOFs) have attracted sustained scientific interest due to their rich functionalities. However, the convergence of these two families, where MOFs adopt the perovskite architecture incorporating neutral X-sites, remains largely unexplored. Moreover, self-healing is notable for its ability to recover from damage, while achieving self-healing in molecular crystals remains a significant challenge. Herein, for the first time, we report a self-healing neutral X-site perovskite ferroelastic crystal (SbF6)Ag(pyrazine)3, in which the neutral pyrazine acts as the X-site, in contrast to the anion X-site in conventional perovskites. It undergoes reconstructive mm2Fm-type ferroelastic phase transition at 163 K and order–disorder 4̅3mFmm2-type ferroelastic phase transition at 322 K. Intriguingly, the reconstructive transition involves reversible breaking of Ag+–N coordination bonds and the formation of weak Ag+···π interactions, which unlocks the self-healing property, distinct from previous reported self-healing mechanisms in molecular crystals. The low-temperature reconstructive transition generates a spontaneous strain nearly ten times larger than that of the high-temperature transition, leading to crystal microcracks that are subsequently healed upon reversible phase recovery. Our discovery opens up a novel strategy to realize self-healing in molecular crystals and demonstrates the neutral X-site ABX3-type perovskites as a fertile ground for multifunctional materials.
Chen et al. (Tue,) studied this question.