Innovative materials chemistry strategies for engineered-enhanced thermomaterials for barocaloric and related solid-state refrigeration

Abstract

The present PhD Thesis focuses on the search of new thermomaterials (materials that have large latent heat associated to a solid-solid phase transition), specifically hybrid organic-inorganic materials, with the aim of exploring their potential use in cooling applications. There is an urgent need to develop alternatives to current refrigeration in order to address the climate and energy challenges that our society is living in order to move towards a carbon-neutral economy with more energy-efficiency, no greenhouse gases emissions, and which relies solely on renewable energy sources. In this context, solid materials are considered attractive options to replace current technologies. Taking this into consideration, the current PhD Thesis investigates three different families of hybrid organic-inorganic materials with potential applications as refrigerants in solid-state refrigeration: hybrid dicyanamide perovskites, hybrid ionic plastic crystals, and metal-organic frameworks (MOFs). On one hand, the structural distortions of hybrid dicyanamide perovskites family were studied and explored, the tolerance factor for this family was revisited, and their first solid solution was prepared. On the other hand, three ionic plastic crystals were tested for their use in barocaloric refrigeration: [Cp2M][PF6] (Cp = C5H5 and M = Fe, Co) and [DBA][BF4] (DBA = dibutylammonium). Lastly, the thermal response of a flexible MOF with a solid-solid phase transition linked to adsorption/desorption of carbon dioxide process upon the application of low pressure was measured: the MIL-53(Al) with general formula [Al(OH)(C8H4O4)]. It is worth noting that in addition to assessing the viability of some materials from these families as solid-state refrigerants, significant emphasis has also been placed on the search for design tools for new materials to provide guidelines that contribute to the development of solid-state refrigeration.