含亲水性磺酸基的羧酸配体构建的金属-有机框架及其质子传导性能

Proton-conductive materials, being at the heart of the proton exchange membrane fuel cell, are an important class of materials for energy conversion in fuel cell. The performance of the fuel cell significantly depends on the chemical and physical properties of the proton-conductive materials. Rational design and synthesis of the proton-conducting materials with excellent performance and clarifying the structure-activity relationship between the microstructure and proton conductivity at the molecuar level are still a big challenge for scientists. Based on the fact that the bifunctional sulfonate-carboxylic ligands containing strong coordination ability of the carboxylic group and relatively weaker coordination ability of the sulfonate group exhibiting discriminative coordination abilities, the construction of the proton-conductive metal-organic frameworks (MOFs) based on the carboxylic ligands containing highly hydrophilic sulfonate groups is proposed here. The sulfonate group with facile protonated and deprotonated characters being orderly arranged at the surfaces of the pores or the layers of the MOFs will serve as the binding sites for the protons. Thus the sulfonate groups in the MOFs are the components of the proton-conduction pathway and facilitate the enrichment of the water molecules around them and the high-performance transport of the protons. The expected proton-conducting MOFs working at the low-temperature and high-humidity with high performance can be synthesized by modulating the sulfonate-carboxylic ligands and lanthanide or alkaline earth metal ions. At the same time, the composite MOFs materials working at an intermediate-temperature with high proton conductivity will be obtained by encapsulating the proton-carrier molecules such as imidazole into the channels of the porous sulfonate-carboxylic MOFs constructed from the highly charged metal ions. The long-range ordered structure of crystalline MOF provide a platform for investigating the structure-activity relationship between the microstructure and proton conductivity of the MOFs, which will provide deeper insights for clarifying the proton-conductive mechanism of the MOFs and basic experimental knowledge for the application of MOFs in fuel cells.

质子传导材料是质子交换膜燃料电池的核心部件，对燃料电池的性能起着关键作用。但合理设计合成优良性能的质子传导材料并在分子水平上揭示材料微观结构与质子传导性能间的构效关系仍面临巨大挑战。本项目巧妙地利用羧酸基配位能力强，而磺酸基配位能力弱且具有强亲水性和可快速质子化和脱质子的特点，来构建新颖的含磺酸基的羧酸金属-有机框架（MOF）质子传导材料，磺酸基有序地排列在MOF孔/层表面用于富集水分子和构筑质子传递通道。通过采用不同的磺酸基-羧酸配体和稀土、碱土等金属离子合成结构多样的MOF化合物，以获得性能优良的低温高湿质子传导材料。同时，将咪唑等质子导体植入到由高价金属离子构筑的多孔磺酸基-羧酸MOF的孔内，以构建中温区质子传导材料。MOF的晶态结构能够在分子水平上研究材料微结构与质子传导性能之间的构效关系，为揭示MOF材料的质子传导机理提供翔实的实验依据及在燃料电池方面的应用提供实验基础。

质子交换膜燃料电池由于高效清洁的特点受到市场的广泛关注，其核心部件之一是质子传导材料，它的性能直接决定了燃料电池的性能。现有的质子传导材料为有机高分子聚合物，高分子聚合物长程无序的结构不能形成长程开放的质子传递通道，影响质子的传递。另外，高分子聚合物无定型的结构特点阻碍了其构效关系和质子传导机理的阐明。因此，探寻新型高性能的质子传导材料并阐明其质子传导机理，对推动燃料电池产业的发展具有深远的意义。. 本项目利用磺酸-羧酸配体来构建金属-有机框架（MOF）质子传导材料，巧妙地利用羧酸基配位能力强，而磺酸基配位能力弱且具有强亲水性和可快速质子化和脱质子的特点，来构建MOF质子传导晶态材料，羧酸基团与金属离子配位形成MOF的主体框架，磺酸基有序地排列在MOF孔/层表面用于富集水分子和构筑质子传递通道。本项目合成了四种新型的磺酸-羧酸配体，以这些配体与金属离子合成了一系列结构多样的MOF。其中，有些MOF的质子传导率高达10-3 S cm-1，可与商业的质子传导材料相媲美。这些研究结果为质子传导材料的设计合成提供了新的研究思路。项目实现了MOF的传递途径和导电机理的阐明，发现磺酸基团对这些MOF的质子传导性能起着决定性的作用，更为重要的是，在MOF中发现了磺酸基团，水分子，羧酸基团之间形成了连续的氢键网络是质子传递的路径，在原子水平上揭示了质子在MOF中的传递通道，为研究质子传导材料的质子传导机理提供了范例，为质子传导材料的研发提供了重要的借鉴作用，推动了质子传导材料的发展，为燃料电池的应用提供了材料基础。.项目研究成果发表SCI科研论文24篇，部分成果在无机化学领域权威期刊Inorganic Chemistry（8篇）和Inorganic Chemistry Frontiers（1篇）上发表。论文的被引次数超过300次，形成了较大的学术影响力，在磺酸基-羧酸配体MOF领域形成了独特的研究特色。申请发明专利3项，培养了6名硕士研究生，其中两位研究生的学位论文被评选为江西省优秀硕士学位论文，因此项目产生了高质量的学位论文和培养了优秀的研究生。