Controversy on the ferroelectricity in metal–formate frameworks

The metal–organic frameworks (MOFs) crystallizing in a perovskite-like architecture became extremely interesting for scientists due to a variety of applications including memory devices, energy conversion and drug delivery. These compounds are constructed from a metal–oxygen or metal–nitrogen octahedral coordinated by organic ligands. They exhibit various interesting properties due to their hybrid organic–inorganic nature. However, ferroelectric MOFs still remain scarce and the topic of ferroelectricity raises a lot of controversies. In this article, we will discuss the actual state of knowledge of these specific compounds with a focus on ferroelectric properties. We will try to create an order out of the current confusion that followed attributing ferroelectric properties to metal–formate frameworks without a direct proof.