Hybrid organic-inorganic perovskites (HOIPs) are a huge class of crystalline materials with general formula ABX3, where A, B and X are an organic cation, metal cation and multidentate inorganic or organic anion, respectively. HOIPs have recently emerged as efficient optoelectronic materials thanks to their valuable utility in to ionic transport, 1,2 multiferroic 3 and photovoltaic applications. They possess a high chemical and structural variability through the replacement of the X species with other multidentate bridging ligands such as cyanide [CN -], thiocyanate [SCN -], formate [HCOO -], hypophosphite [H2POO -] or dicyanamide [dca, N(CN)2 -], among others. Careful selection, or modification of the linker and/or metal cation allows property modulation and enhancement. The extended hybrid connectivity of HOIPs mean that they share many similarities with metal-organic frameworks (MOFs). However, HOIPs are considerably more dense than MOFs given the presence of the A-site cation, which means they are typically unable to selectively adsorb guest species. Accordingly, interest in their behaviour does not revolve around porosity, but instead concentrates on ionic conductivity, 1 ferroelectric and barocaloric properties.