Other Perovskite‐Like Hybrid Materials and Metal‐Free Perovskites

This chapter provides a detailed discussion on the synthesis, structural diversity, phase transitions, and physical properties of hybrid organic–inorganic perchlorates, hybrid organic–inorganic tetrafluoroborates, and metal-free perovskites. Using ClO4 - as an X-site bridging ligand can produce a new family of ABX3-type hybrid organic–inorganic perchlorates. The hybrid organic–inorganic perchlorates exhibit rich phase transitions, and most of structural transitions are the order–disorder type. Employment of BF4 - as the X-site bridging group can lead to a new series of ABX3 perovskite-like hybrid organic–inorganic tetrafluoroborates templated by different organic diamine cations. All metal-free perovskites can be easily synthesized by using stoichiometric starting materials in aqueous solution. Metal-free perovskites crystallize in diverse symmetries at ambient conditions, which include the monoclinic, orthorhombic, trigonal, and cubic systems.