分子基稀土低温磁制冷材料的构筑与磁热效应调控研究

Due to their diversity, easy controllability and superior capability, molecule-based cryogenic magnetorefrigerant materials are becoming a new hotspot in the research of novel refrigerant materials. Since isotropic gadolinium ion possess a large-spin ground state, low-lying excited spin states and relatively large shielding effect, and short-bridge ligands (such as nitrate, carbonate, sulfate, etc.) exhibit various coordination modes and small molecular weight, the complexes assembled by them most likely display weaker magnetic coupling and larger magnetic density, which are expected to be novel molecular rare earth cryogenic magnetorefrigerant materials. This project is to prepare molecule-based rare earth magnetorefrigerant materials with a large entropy change in low fields by assembly of gadolinium ion sources and organic ligands like methylthionine chloride, thiolate and dicarboxylate that are prone to be active in an in situ reaction under hydro/solvothermal conditions. We can reveal the in situ assembly mechanism of such materials. Through the change of ligands and reaction conditions, the control of structures and magnetism of target complexes will be realized and the law of the structural and magnetocaloric effect (MCE) regulation can be further summed up. On this basis, magneto-structural relationship will be in-depth studied by combining with theoretical calculations and the main factors of MCE will be clarified. Therefore, general rule of the construction of the materials would be obtained and their related performance would be improved. The project will provide the scientific theory basis of the preparation, properties and application of novel molecular rare earth cryogenic magnetorefrigerant materials.

分子基低温磁制冷材料因其种类多、可控性强和性能优越等特点，正成为新型制冷材料的研究热点。由于各向同性的钆离子具有较大基态自旋、低的激发态以及较大的屏蔽效应，而硝酸根、碳酸根、硫酸根等短桥配体具有丰富的配位模式和较小的分子量，两者组装的配合物极有可能具有较弱的磁耦合和较大的磁密度，有望获得新型分子基稀土低温磁制冷材料。本项目拟选用易原位生成短桥配体的亚甲基蓝、巯基类和二元羧酸类配体以及钆离子源为主反应物，通过水热或溶剂热反应等来构筑低场大磁熵变的分子基稀土磁制冷材料，揭示这类材料原位组装机理。通过改变配体结构和反应条件，实现对配合物的结构和磁性能的控制，进而总结出目标产物的结构和磁热效应调控的规律。在此基础上，结合理论计算，深入研究钆配合物的磁构关系，阐明影响磁热效应的主要因素，获得构筑这类材料与改善其性能的普遍规律，为新型分子基稀土低温磁制冷材料的制备、性能研究及应用提供科学的理论依据。

随着人们对能源和环境问题的日益重视，磁制冷技术的开发和研究备受关注。近年来，分子基磁制冷材料由于可能在超低温制冷技术上替代稀缺和昂贵的He-3已成为化学、物理和材料学研究的热点和前沿领域之一。在本项目的研究中，我们选用三类羧酸配体为构筑块，与钆离子进行组装构筑了具有优良制冷性能的分子基稀土低温磁制冷材料，并研究了其构效关系。此外，我们揭示了这类材料的组装过程的机理及配体改变对化合物结构调控的基本规律，深入研究了其磁性能，获得适合构筑这类材料与改善其性能的普遍规律，为开发具有实际应用价值的磁制冷材料奠定了基础。在稀土低温磁制冷材料、其他分子基磁性材料以及金属-有机框架材料的组装、调控、结构及其性能研究等方面取得了系列创新成果，相关成果已在Inorganic Chemistry、Crystal Growth & Design、Dalton Transactions、CrystEngComm、New Journal of Chemistry等国际重要学术刊物上发表。发表SCI论文40篇，其中第一作者或通讯作者论文23篇；申请发明专利9件，其中授权发明专利5件；应邀在2016年中西部地区无机化学化工学术研讨会和江西省化学化工学会2018年学术年会上做报告，受到国内外同行的关注和好评。