Solid-state refrigeration based on caloric effects provides a sustainable alternative to conventional vapor-compression cooling technologies that rely on environmentally harmful refrigerants. Among these approaches, the barocaloric effect (BCE) has attracted considerable interest; however, structural phase transitions typically require high driving pressures, which severely restricts their practical applications. In this work, we investigate the BCE in a family of metal-organic frameworks (MOFs) featuring a wine-rack topology, revealing that these structures can achieve giant entropy changes under remarkably low pressures. Specifically, MIL-53(Al) exhibits an entropy change of $108\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$ at 40 MPa, while MIL-53(In) achieves $188\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$ at only 15 MPa, comparable to the required pressure in commercial vapor-compression refrigeration. A physically interpretable model constructed using the SISSO (sure independence screening and sparsifying operator) algorithm reveals that the low driving pressure in these systems primarily originates from a small bulk modulus and a large pore volume; meanwhile, lower linker mass density and larger metal-ion radius effectively attenuate local steric hindrance and interatomic interactions, similarly facilitating the low-pressure-driven phase transitions. Thermodynamic decomposition of the energy demonstrates that this giant entropy change is dominated by the potential energy variation associated with framework deformation, wherein the van der Waals interactions between the organic linkers play a crucial role. Microscopic phonon dynamics analysis further elucidates that the pressure-induced framework contraction concentrates substantial local stress on the carbon atoms, suppressing their low-frequency vibrational modes and thereby leading to a reduction in the vibrational entropy of the system. These results identify wine-rack MOFs as promising candidates for low-pressure barocaloric refrigeration, providing structural design principles for high-performance solid-state cooling materials.

Close

PrevNext

View figure in article

• Entropy
• Pressure effects
• Solid-state refrigeration
• Thermodynamics
• Metal-organic framework
• Deep potential molecular dynamics
• Density functional calculations