Doheny Patrick W, Cassidy Simon J, Saines Paul J
School of Physical Sciences, University of Kent, Ingram Building, Canterbury CT2 7NH, U.K.
Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K.
Inorg Chem. 2022 Mar 28;61(12):4957-4964. doi: 10.1021/acs.inorgchem.1c03688. Epub 2022 Mar 14.
The development of sustainable and efficient cryogenic cooling materials is currently the subject of extensive research, with the aim of relieving the dependence of current low-temperature cooling methods on expensive and nonrenewable liquid helium. One potential method to achieve this is the use of materials demonstrating the magnetocaloric effect, where the cycling of an applied magnetic field leads to a net cooling effect due to changes in magnetic entropy upon application and removal of an external magnetic field. This study details the synthesis and characterization of a Ln(adipate)(DMF) series (where Ln = Gd-Er) of metal-organic framework (MOF) materials incorporating a flexible adipate ligand and their associated magnetocaloric and thermal expansion properties. The magnetocaloric performance of the Gd(adipate)(DMF) material was found to exhibit the highest magnetic entropy changes of the series, with a peak entropy change of 36.4 J kg K for a 5-0 T field change at a temperature of 2 K, which is suited for ultra-low-temperature cooling applications. Thermal expansion properties were also investigated within these materials, demonstrating modest negative and large positive thermal expansion identified along the different crystallographic axes within the MOF structures over a 100-300 K temperature range that demonstrated the novel mechanical properties of these adipate framework structures.
目前，可持续且高效的低温冷却材料的开发是广泛研究的主题，其目的是减轻当前低温冷却方法对昂贵且不可再生的液氦的依赖。实现这一目标的一种潜在方法是使用具有磁热效应的材料，在施加和去除外部磁场时，由于磁熵的变化，施加磁场的循环会导致净冷却效应。本研究详细介绍了一系列包含柔性己二酸配体的金属有机框架（MOF）材料Ln(己二酸)(DMF)（其中Ln = Gd - Er）的合成与表征，以及它们相关的磁热和热膨胀特性。发现Gd(己二酸)(DMF)材料的磁热性能在该系列中表现出最高的磁熵变化，在2 K温度下，5 - 0 T的磁场变化时，峰值熵变为36.4 J kg K，适用于超低温冷却应用。还对这些材料的热膨胀特性进行了研究，结果表明，在100 - 300 K的温度范围内，沿着MOF结构内不同的结晶轴，分别呈现出适度的负热膨胀和较大的正热膨胀，这展示了这些己二酸框架结构的新颖力学性能。
