Metal organic frameworks MOF CdIF-13 with CO₂ gas absorption as new ecological cooling systems

Most refrigeration systems rely on hydrofluorocarbon (HFC) gases with global warming potentials 2000 times higher than CO₂. Eco-friendly refrigerants are thus needed. Flexible metal-organic frameworks (MOFs), such as MIL-53(Al), have a promising thermal response associated with structural transitions due to adsorption of CO₂ molecules into nanoporous cavities. While initial studies demonstrated the potential of adsorption-driven caloric effects, they were limited to breathing transitions, involving gradual, cooperative changes in unit cell volume. We aim to investigate a fundamentally different and unexplored mechanism—gate-opening—characterized by a sudden and well-defined pore access transition. A detailed structural understanding under varying CO2 pressures and temperatures is required. We propose in situ powder X-ray diffraction (PXRD) experiments at variable CO2 pressures and temperatures to determine structural changes and construct comprehensive phase diagrams of MOF CdIF-13.