ABX3 Perovskite Coordination Networks as Barocalorics

• Applicant: Dr. Gregor Kieslich
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 450070835

The barocaloric effect provides a fascinating opportunity for the creation of next-generation, sustainable refrigeration processes. The barocaloric technology only comes to fruition if green, inexpensive and easy processable materials are discovered that show a large barocaloric performance, i.e. large reversible thermal changes in response to low hydrostatic pressure. The absence of synthetic guidelines for the synthesis of high-performance barocaloric working-media is limiting any systematic development of the field. The research concept and outcomes of this proposal aim to fill this gap by combining a fundamentally motivated research concept with a subject boundary crossing research perspective.The research proposal is based on the working hypothesis that the barocaloric performance of a material is fundamentally related to its bulk modulus. Thus, the bulk modulus becomes the link between synthetic chemistry and the barocaloric properties of a working medium, representing an intriguing basis for the development of a guideline for the targeted synthesis of high-performance barocalorics. To verify this hypothesis, a chemically versatile material platform is required that offers the chemical parameter space for systematically studying the bulk modulus and the barocaloric properties as a function of small chemical changes. Only such an approach is expected to lead to fundamental and sustainable knowledge that has the potential to mature the field. I propose to apply ABX3 Perovskite Coordination Networks (PCNs) as material platform to test, evaluate and refine the working hypothesis. Akin to inorganic perovskites, PCNs crystallise in the well-known perovskite structure motif with molecular building units on the A and X-site. The use of molecular moieties leads to a large chemically diversity with over 200 reported PCNs, of which more than 25 show phase transitions interesting for the barocaloric application. Some PCNs have recently been discovered to exhibit so-called giant barocaloric effects, making PCNs to the first available materials class in the field that shows promising barocaloric properties. Based on the chemical diversity of PCNs, the proposed research plan lays the scientific foundation for the targeted design and synthesis of PCNs with high-barocaloric performances. The workplan follows a systematic and interdisciplinary research approach, ranging from the synthesis of tailor-made molecular building blocks to high-pressure crystallography and calorimetry. After verifying the working hypothesis, the targeted optimisation based on the acquired knowledge is approached with the research goal of identifying design principles for PCNs with high barocaloric performances. The proposal builds on my group's expertise in the structure and thermodynamic analysis of PCNs and gives me the unique opportunity to shape one of the most exciting developments in the field of applied coordination networks right from the start.

• DFG Programme: Research Grants