具有氙气吸附性能的晶态多孔有机框架材料的定向合成

Xenon represents the most important member of noble gases with diversified applications in illumination, optics, medicine, NMR, and etc. Due to the inert chemistry of xenon and its scarcity in air, developing an effective way to produce xenon has become a hot topic. Sorption using porous adsorbents has become a favorable method because of the low energy consumption, economy, reproducibility, and so on. Porous organic frameworks (POFs) is proposed as an excellent candidate as an adsorbent because POFs possess high surface areas, tunable microporous structures, and high stabilities. From the perspective of materials, our project is intended to develop novel crystalline POFs with superior sorption performances toward xenon in terms of high capacity and high selectivity. The main content of this project includes: (1) controllable syntheses of crystalline POFs with suitable pore sizes, comprehensive understanding of the formation mechanism of POF crystals, and investigation on the relationship between pore structures of POFs and xenon sorption properties. (2) Preparations of crystalline and functionalized POFs will be carried out with a focus study on the interactions between functionalities in POFs and xenon molecules. (3) The evaluation of crystalline POFs toward xenon sorption will be conducted in order to unveil the key parameters governing the sorption properties. Through the implementation of this project, it is expected to develop high-quality crystalline POFs with good abilities of xenon sorption and storage.

氙气是一种重要的稀有气体，广泛应用于照明、光学、医学、核磁共振等。由于氙气的化学惰性及极低浓度，因而寻找一种高效生产氙气的方法成为研究热点。基于多孔材料的吸附法具有低能耗、经济实用、重复性高等特点。多孔有机框架材料（Porous Organic Frameworks, POFs）由于高比表面、可调微孔结构、高稳定性，成为制备高效多孔吸附剂的理想材料。本项目主要从材料角度出发，通过定向构筑对氙气具有高吸附量、高选择性的晶态POFs材料。具体研究内容拟从以下三方面详细展开：（1）精确合成具有合适孔道大小的晶态POFs，深入理解晶态POFs的形成机理，探究孔道大小与氙气吸附性能的关系。（2）制备具有功能化的晶态POFs，研究功能团与氙气分子之间的作用关系。（3）晶态POFs对氙气吸附性能的评估，掌握POFs材料中对氙气吸附起关键性作用的因素，实现可控制备高效的POFs材料应用于氙气吸附和存储。

本项目主要围绕着一下三个方面进行展开：（1）制备结构可调的晶态多孔有机框架材料：通过选择三节点的短链有机分子，通过离子热及耦合反应，合成了晶态及准晶态的超微孔有机材料。合成的CTF-0, PAF-45, PAF-67的孔道大小约为5.0 Å，比表面积为528.4-951.4 m2/g，微孔体积为0.158-0.286 cm3/g。以二节点NTCDA和三节点TAPA单体交替连接的方式，构筑了二维六方结构的PAF-110晶态材料。合成的PAF-110的孔道大小为26 Å、比表面积为910 m2/g。以四节点单体DTM1和DTM2，通过自聚的方式，合成了具有金刚石拓扑的超空旷结构。合成的PAF-100和PAF-101的孔径大小为1.4 nm和1.3 nm。V-字型配体4,4’-sulfonyldibenzoic acid与金属钙离子配合连接成了一维孔道结构，CaSDB孔道大小约为5.0 Å。（b）晶态多孔有机框架材料的功能化：利用磺化的手段，在PAF-45S骨架上引入了磺酸基，每四个苯环共享一个磺酸基团。以带羧酸基团的二胺2,5-diaminobenzoic acid (DAA)为构筑单元，构筑了羧基、含钙、含锶、含锰的MOOC-COFs晶态有机框架材料。通过交换单体的方式，合成了含有吸附位点和水解位点的MIPAFs 1-9九个化合物。（c）晶态多孔有机框架材料的气体吸附：我们根据孔化学的基本原理，探讨了多孔有机框架材料在吸附分离中的应用。我们探讨了小孔的CTF-0, PAF-45, PAF-45S, PAF-67, CaSDB对氙气氪气的吸附及分离。吸附测试结显示PAF-45, PAF-45S, CaSDB对氙气/氪气的分离比分别是8.1, 16.7, 20.5。开发了PAF-110在乙炔/乙烯分离的应用，PAF-110对乙炔的吸附量为3.48 mmol/g，乙炔/乙烯分离比为3.9-8.0。探索了PAF-100与PAF-101对甲烷的存储能力，PAF-100与PAF-101对甲烷的最大吸附量高达742和622 cm3/g。评估了MOOC-COFs在氨气封存方面的潜力，其中在298 K下MOOC-COFs对氨气的吸附量为14.3 mmol/g。总之，我们开展了晶态多孔有机框架材料的设计合成、功能化、气体分离与存储三方面的研究工作。