缺陷工程MOFs材料的设计及其对ANG系统的性能强化策略

Metal-organic frameworks (MOFs) have drawn widespread attention for vehicular adsorbed natural gas (ANG) technology, due to their large adsorptive capacity and highly tunable structures. However, Application of MOF-based ANG is hampered by two significant challenges, i.e. the accumulation of impurities from natural gas and the structural degradation of MOFs, which would likely lead to irreversible decrease in the capacity of ANG system. Due to the time-consuming nature of experiments with long-term cycling and the challenge of analyzing trace impurities, experimental study of impurity accumulation and developing mechanically stable MOFs for ANG systems has been limited. To overcome these issues, combining computational and experimental approaches, we propose to design defect-engineering MOFs from well-tuning the linker composition and distribution of double-liker MOFs, and develop a mathematical ANG model to quantitatively determine the regeneration strategy for the system. The proposed work will focus on (1) fundamentally understanding the mechanism of metal center-linker bond breaking resulted from the impurity attack, the influence of linker length, size and functional groups on the stability of linkers, and the effects of regeneration period, temperature and pressure on the deliverable energy of the system; (2) optimizing the linker composition and distribution of double-liker MOFs, so as to maintain the stability of the defect-engineering MOFs during the ANG cycling, and developing ANG model to estimate the degree of impurity accumulation and the working life time of the material, in order to optimize the regeneration strategy for the ANG system. The results of this work provide a novel strategy to design MOFs for overcoming the drawback of capacity decrease of ANG system, which is of significance to facilitate the popularization of vehicular ANG technology in practical applications.

针对车用ANG（Adsorbed Natural Gas）系统中，由于MOFs（Metal-Organic Frameworks）结构坍塌和杂质累积两大关键因素导致系统性能衰退的问题，本项目提出研究缺陷工程MOFs及其对ANG系统的性能强化策略。通过调控双配体MOFs中易受杂质攻击的配体的比例和分布，使MOFs在ANG循环中转化成结构相对稳定的缺陷工程材料，并辅以有效的除杂再生策略，使ANG系统保持稳定的能量输出。从理论角度，研究缺陷形成机理和配体稳定性的影响因素；研究再生周期、压力和温度对ANG系统能量输出的影响。从优化角度，优化两种配体的比例和分布，以维持MOFs结构稳定；建立ANG过程模型，预测材料的使用寿命，并优化再生策略，利用缺陷提高材料的吸附容量和抗杂质能力。本项目成果将为解决ANG材料性能衰退这一难题提供新思路，对促进车用ANG技术的普及化具有重要的科学意义和社会价值。

针对车用ANG（Adsorbed Natural Gas）系统中，由于MOFs材料结构随机缺陷的影响，导致系统性能衰退的问题，本项目提出研究缺陷工程MOFs对ANG系统的性能强化机制。通过计算模拟、机器学习和实验结合，从理论层面上，探究了MOFs受到水分子攻击而导致“配体缺失”缺陷的作用机制，并定量研究MOFs缺陷的含量和分布对其结构稳定性和吸附性能的影响规律。从技术层面上，提出了一种有效的MOFs缺陷定量表征策略，基于机器学习模型，能够从实验易于表征的结构物理量预估真实材料的缺陷程度，从而克服了实验上定量表征MOFs结构缺陷的技术困难。从应用层面上，建立了涵盖多种拓扑类型和结构单元的虚拟MOFs缺陷结构数据库（约40万种），基于数据库，预测了缺陷MOFs的天然气吸附容量极限可达0.65 g/g，略超过美国的天然气汽车储气标准（0.50 g/g）。本项目研究成果为利用MOFs的晶体缺陷强化其吸附性能这一难题提供新的理论基础和普适的解决方案，对促进缺陷工程技术的广泛研究和车用ANG技术的普及化，具有科研和应用层面上的双重价值。. 经过3年研究，项目负责人已发表第一作者/通讯作者SCI论文13篇，包括Chem. Mater., AIChE J., Chem. Eng. Sci., Chem. Eng. J., ACS Appl. Mater. Interfaces等，均已标注基金项目号，申请中国发明专利3项。