柔性多孔配位聚合物的制备及其在甲烷存储领域的应用

How to improve the energy density of methane under ambient conditions is the key problem and main challenge. One promising way of increasing energy density at ambient conditions is to use tanks containing porous materials as a storage medium. However, no porous material yet offer working capacity that approach the DOE target for natural gas storage. Based upon the literature and our previous study, the most efficient way to improve methane working capacity is to increase methane uptake at high pressure, but at the same time, reducing the uptake at low pressure. Therefore, the current project aims to construct a new family of flexible coordination polymers that exhibit tunable gate opening between non-porous (closed) and porous (open) phases at specific methane pressures, enabling their methane working capacity or energy density. First, design and synthesize a new family of flexible coordination polymers. Then study the thermodynamics and kinetic mechanism of the action between methane and flexible coordination networks, revealing the relationship between dynamic structural changes and methane storage performance. Finally, try some of the flexible porous coordination polymers for efficient natural gas storage when their engineering performance have been improved. Therefore, these study will provide new ideas for the controllable synthesis of flexible coordination polymers, will provide theoretical basis for understanding the phase transition mechanism, and will have important implications for the development of on-board natural gas storage technology and the realization of DOE storage targets.

如何提高甲烷在常温和低压下的能量密度是本领域的核心问题和主要挑战。利用多孔材料吸附甲烷被认为是一种有效的解决途径，但是到目前还没有一种多孔材料能达到美国能源部（DOE）提出的甲烷存储目标。文献和我们以往的研究表明，提高材料在高压下的吸附量同时降低其在低压下的吸附量是提高有效甲烷工作量（能量密度）的最有效途径。基于以上认识，本项目拟利用柔性框架材料结构相变导致的 “阶梯型”吸附线来提高甲烷在室温和低压下的能量密度。即首先通过分子结构设计，合成系列新型的柔性配位聚合物；然后研究甲烷分子与柔性框架作用过程的热力学和动力学机理，揭示材料的动态结构变化和甲烷存储性能的关系；进而通过工程性能改进，尝试部分材料在天然气存储方面的实际应用。本项目的研究将为柔性配位聚合物的可控合成提供新的思路，为理解柔性框架材料的动态响应行为提供理论依据，对DOE存储目标的实现和车载天然气存储技术的发展有着重要的意义。

多孔配位聚合物作为一类新兴的多孔材料，具有大的比表面积、可调的孔尺寸和孔化学环境，在气体储存和气体分离领域表现出重要的应用价值。理论上，我们能够根据目标任务需求，设计制备具有特定化学功能的多孔框架材料，并利用其晶态结构的特性，深入研究其吸附机理。本项目在执行过程中，利用量子化学理论计算以及原位晶体学对多孔框架材料的吸附机理进行了深入的研究，并据此设计合成了系列新型镍基多孔框架材料，实现了高性能的气体储存和分离。例如，针对甲烷等能源气体在低压和常温下能量密度低的问题，提出利用柔性多孔配位聚合物特有的结构相变来提高气体的存储密度；针对四氟化碳（CF4）、三氟化氮（NF3）、六氟化硫（SF6）等电子气体回收的难题，制备得到系列具有选择性识别含氟电子气体的多孔框架材料，实现了痕量电子气体的回收。基于该项目的支持，在Angewandte Chemie International Edition， ChemSusChem，ACS Catalysis，ACS Applied Materials & Interfaces,等权威学术期刊发表13篇标注论文。