新型柱[5]芳烃萃取剂的合成及其对锕-镧系元素分离的研究

It is one of the frontiers in nuclear science today to apply novel supramolecular recognition materials to the separation of actinide and lanthanide elements. In the present project a series of novel types of pillar[5]arene extractants are desigend and synthesized by introducing several chelating groups such as phosphonate ester, carbamoylmethylphosphine oxides, pyridine carboxamide, amide pyrazine and phosphine oxide for selective separation of actinides and lanthanides. The investigation is based on our recent work in exploring the possibility of using pillar[5]arene as preorganization platform. The related research has never been documented except for our articles so far. The relationship between pillar[5]arene assisted preorganization and recognition of actinide and lanthanide ions, cooridnation behaviour and extraction performance will be investigated via tuning the structure of multiple chelating groups, spacer linkage and coordinating atoms. With the aid of computer modeling, the mechanism of extraction that is responsible for the difference in Ln/An group separation will be expounded. The efficiency of extractants will be appraised based on several aspects including their coordination chemistry, acidity, extraction and back-extraction ability, as well as irradiation stability to disclose the controlling factors and laws that govern the solvent separation process. This work will pave the way for providing a new class of pillararene extractanns with potential applications.

新型超分子萃取剂用于镧锕离子组分离是当今核科学研究的前沿方向之一。基于本课题组已开展的柱[5]芳烃作为预组织平台的超分子萃取剂的探索工作，本项目设计在柱[5]芳烃骨架上引入具有配位作用的膦酸酯、氨基甲酰甲基氧膦、吡啶酰胺和酰胺吡嗪氧化膦功能基团，合成一系列用于镧-锕元素分离的新型柱[5]芳萃取剂。借助平台的预组织作用和配位基的螯合作用实现对镧锕系离子的选择性配位和萃取分离，该研究除本课题组外至今国内外还没见其它相关报道。通过考察柱[5]芳烃预组织结构与镧锕系离子识别、配位行为及萃取性能的关系，并借助计算机分子模拟，阐释导致镧-锕系元素组分离选择性和效率差异的萃取分离机制，并从配位化学、酸度、萃取与反萃效率及辐射稳定性等方面对萃取剂进行评价，揭示该类萃取剂在萃取分离上的主控因素和规律。本项目将为建立一类具有应用前景的新型柱芳烃萃取体系奠定基础。

基于乏燃料后处理过程中面临的离子识别与核素分离难题，开展新型功能材料在放化分离中的应用研究具有重要的意义。利用近年来发展起来的柱[5]芳烃作为预组织平台，结合前期我们对柱[5]芳烃萃取剂的研究基础，依次将氨基甲酰甲基氧化膦、酰胺荚醚、氧化膦、单磷酸酯、磷酸酯、苯甲醛肟、吡啶酰胺、三唑喹啉等引入柱[5]芳烃骨架，建立了柱芳烃系列衍生物的合成路线和方法，并首先探讨了其在有机溶剂体系中对镧锕系离子识别与萃取性能的关系。为了进一步提高其萃取效率和分离因子，将1-辛基-3-甲基-咪唑双三氟甲基硫酰亚胺离子液体(C8mimNTF2)离子液体替代有机溶剂作为稀释剂，研究了该类萃取剂对镧锕离子萃取性能。通过核磁共振一维和二维氢谱、高分辨质谱HRESI-MS、Job plots分析法以及计算机分子模拟等手段，证实了离子液体的咪唑阳离子部分与柱芳烃分子间的主-客体作用，研讨了其萃取平衡过程，并提出了超分子主客体竞争的阳离子交换的萃取机理。实验表明酰胺荚醚修饰的柱[5]芳烃（DGA-柱[5]芳烃）萃取剂在C8mimNTf2中，1.0 M硝酸存在下，该萃取体系能实现对放射性裂变产物Am(III)与Cs(I)、Sr(II)、Pu(IV)、Pu(VI)和U(IV)的分离后，还能进一步实现Pu(IV)与Cs(I)、Sr(II)、Pu(VI)和U(IV)的分离。此外，实验还证实柱[5]芳烃衍生物在γ或辐照下仍表现出良好的辐射稳定性，为进一步发展该类萃取剂用于放化分离提供新的方向和思路。