新型有机骨架材料的设计制备及其在盐湖提铀中的应用基础研究

China is one of the countries that possess rich saline lake resources all over the world. As is well known, saline lakes are particularly rich in uranium and other resources. According to preceding researches, uranium concentration in the Gasikule Saline Lake in Qaidam Basin is much higher than that in seawater. Therefore, to develop suitable functional materials for extraction of uranium from these saline lakes are of great economic and technical importance, especially for the sustainable development of nuclear power in China. Covalent Organic Frameworks (COFs) are novel functional porous materials. Owing to their unique topology, easy to synthesis, modifiable characteristics, COFs have various applications in gas storage, catalysis and optoelectronic materials. By the aid of high-performance computational chemistry simulation, we intend to design, synthesize and characterize new COFs capable of adsorbing uranium selectively. In this project, we will study the adsorption behavior and mechanism in details, and analyze the influence of pH value, ionic strength and counterion on COFs extraction efficiency. Finally, we will apply the obtained COFs in the extraction of uranium from saline lakes. It can be foreseen that, due to the good stability, large surface area, large adsorption capacity, recyclable and cost-effective properties, these COFs are very promising in the area of extraction of uranium from saline lakes.

中国是世界上盐湖最多的国家之一，而盐湖中富含铀等金属和矿物资源。已有研究表明，柴达木盆地的尕斯库勒等盐湖中，卤水中的铀含量远远超越海水中铀的浓度，因此开发适合于盐湖环境的高效提铀功能材料将有效推动中国盐湖的综合开发，对于中国核能的可持续发展意义重大。本项目拟设计合成对铀酰离子具有优良选择性和吸附能力的新型有机骨架材料（COFs），设计过程中借助计算化学和拓扑设计等辅助手段，深入研究COFs材料对铀酰离子的吸附行为与作用机理，考察溶液pH值、温度、离子强度和竞争离子对COFs萃铀效率的影响，探索铀酰离子的脱附条件，测试COFs材料的稳定性和可重复利用率，在此基础上筛选合适的COFs材料进行盐湖环境下的提铀实验研究。本项目设计制备的COFs材料将具备稳定性好、比表面积大、吸附速度快、富集倍数高、易从盐湖水中吸附铀酰离子和容易循环利用等特点，为我国盐湖提铀工业提供扎实的基础。

功能化的多孔材料近年来开始被应用于放射性核素的吸附提取等，并取得了很好的效果。共价有机框架材料(COFs)因其吸附效果强、比表面积大、密度小、耐酸碱性、溶剂稳定性高、且容易合成等优点，近年来倍受大家青睐。. 本项目通过合理的理论和实验设计，采用前驱体修饰法成功制备了含磷酸酯功能化的二维共价有机框架材料，并将其应用于盐湖中铀的吸附研究，系统地研究了pH、时间、初始浓度、竞争离子等多种因素对铀吸附的影响，并采用FT-IR、S-NMR、EXAFs和理论模拟等手段详细地探讨了铀酰离子的吸附机理。主要研究结果如下：成功合成了磷酸酯功能化的共价有机框架材料COF-IHEP1和COF-IHEP2，将其应用于U(VI)的吸附分离，通过FT-IR、PXRD、固体核磁(S-NMR)等手段表征COF-IHEP1 和COF-IHEP2的晶体结构。酸碱稳定性和辐照稳定性实验证实，COF-IHEP1具有很好的耐酸碱和耐辐照稳定性。 吸附结果表明，COF-IHEP1的吸附容量受pH值影响较小，饱和吸附容量高达112 mg/g。机理研究表明材料的磷酸酯基团的P=O与U(VI)离子配位络合。该材料对U(VI)有极好的吸附效果和选择性。该类材料的设计与制备为盐湖提铀应用提供了新的方法。