增强MOFs水汽稳定性的SBU修饰策略及其同时稳定材料结构和性能的机理

Metal-Organic Frameworks (MOFs) are a class of promising adsorbents with high capacity and superior selectivity. However, the stability of most MOFs cannot withstand humidity, which hinders their potential applications. In this project, we have proposed a novel strategy that functionalizes the secondary building unit (SBU) of MOFs, so as to simultaneously enhance their structural stability and adsorptive capacity against moisture. In this way, a series of novel MOFs with high capacity, enhanced steam stability, and superior CO2/CH4 selectivity were developed for biomethane and natural gas upgrade applications. This project will be carried out from the following 3 aspects: (1) From the aspect of mechanism study, the influence of SBU micro-environment on the steam stability, porous structure, and surface chemistry of MOFs will be interpreted. (2) From the aspect of materials fabrication, efficient technologies such as nano-seed assisted ultrafast synthesis and post-synthetic modification will be adopted and optimized, and the relationship between the synthetic conditions and materials’ properties will also be concluded. (3) From the aspect of separation science, the steam stability of the MOFs synthesized in this work will be tested under the moist working conditions, their CO2/CH4/H2O adsorptive equilibrium will be studied, and their competitive adsorptive separation process will be comprehensively investigated. The outcomes of this project will facilitate the applications of biomethane production and natural gas upgrade with novel theoretic and technical foundations, and thus have significance in materials science as well as industrial applications.

针对MOFs材料普遍存在水汽不稳定性制约其应用的瓶颈问题，本项目提出研究增强MOFs水汽稳定性的SBU修饰策略及其同时稳定材料结构和性能的机理。拟通过对MOFs次级结构单元（SBU）的修饰，抑制水分子的进攻，在水汽工况下同时增强材料结构和吸附性能的稳定性，并得到一系列高容量、高水汽稳定性、高选择性的MOFs吸附材料，这是项目特色和创新之处。研究内容涉及：在理论层面，揭示MOFs的SBU化学微环境对其水汽稳定性、孔隙结构和表面化学的影响规律；在材料制备层面，研究纳米晶种法、后合成修饰法进行SBU修饰的新技术；在分离科学层面，围绕我国当前天然气和生物甲烷生产需求，研究CO2/CH4/H2O在材料上的吸附热力学、动力学、选择性，以及其竞争吸附机理和多组分分离过程。项目将为MOFs结构和性能水汽稳定性的同时增强提供新的理论和技术，并为高效分离纯化生物甲烷和天然气的工业应用提供新的科学基础。

针对MOFs材料普遍存在水汽不稳定性制约其应用的瓶颈问题，本项目提出研究增强MOFs水汽稳定性的SBU修饰策略及其同时稳定材料结构和性能的机理。对MOFs次级结构单元（SBU）进行保护性和功能性修饰，抑制水分子的进攻的同时增强材料结构和吸附性能的稳定性，得到一系列高容量、高水汽稳定性、高选择性的MOFs吸附材料。主要进展包括：（1）提出了基于有机碱、氨基酸的小分子修饰及二维复合的SBU调控策略，制备出一系列具有良好水汽稳定性和吸附分离性能的新型MOFs吸附剂，其中一种有机碱修饰的Cu-BTC不仅在水汽工况下保持良好的结构稳定性，常温常压下的CO2容量高达5.9 mmol/g，从甲烷或者氮气中捕获CO2的选择性分别达到9.5和95，位于同类材料的先进水平前列；（2）结合分子模拟与实验表征，揭示了SBU调控增强MOFs水汽稳定性和CO2吸附分离性能的机理，说明SBU调控主要通过竞争配位与空间位阻效应提升水汽稳定性，通过多孔结构强化、表面化学改性、孔道限域协同机制强化吸附分离性能；（3）开发了新型吸附剂的常温快速制备技术，并以新型吸附材料为核心建立了从甲烷或氮气中一步捕获CO2的固定床分离过程，为其工业应用基础提供技术支持。该研究成果围绕化工分离的实际需求，解决MOFs材料用作工业吸附剂的瓶颈问题，以高效分离纯化生物甲烷和碳捕获为应用背景，为MOFs基工业吸附剂的设计和开发提供新的理论和技术路线。此外，还衍生出一系列用于石化行业低碳烃分离的烷烃选择性吸附剂，具有重要的科学意义和实际的工业应用前景。