新型纳米铁基MOF复合材料及其强化CO2/N2/H2O吸附分离机制

It is rise to new challenge of a sharp decrease in separation efficiency due to the competitive adsorption of water vapor in CO2 capture by Metal-Organic Frameworks. In this project, it is to prepare the novel nano iron/MOFs composite, and then investigate their adsorption separation mechanism of CO2/N2/H2O. From the theoretical point of view, the effects of surface chemical properties of the nano iron/MOFs composites on the adsorption equilibrium, kinetics, and selectivity will be discussed. By optimizing of iron-based particles size and chemical properties, first layer water adsorption adsorbed could become partially or completely dissociation dissociated to form a surface containing OH. Since the surface containing OH is alkaline, thus it could become an alkaline active site for adsorption of acidic CO2 molecule, which resulted in enhanced CO2 capacity and selectivity of CO2/N2. Technically, through the design and control of the structure, the nano iron/MOFs composites should possess high adsorption capacity and high selectivity of CO2/N2 at high humidity. It is investigated that the CO2 capture from gas mixtures by nano iron/MOFs composites used as a key adsorbent at high humidity. The research results of the project have important application value and scientific significance.

针对吸附捕获CO2时，普遍存在混合气中水汽强竞争吸附导致分离效率急剧下降问题，本项目提出研究纳米铁基/MOF复合材料及其吸附分离CO2/N2/H2O机理。理论层面上,研究和揭示新型铁基/MOF复合吸附剂的表面物化性质对CO2、H2O和N2 吸附相平衡、动力学和分离选择性的影响规律；优化调节铁基粒子尺寸和化学性质，促进表面吸附H2O的解离,形成更多碱性活性位，增强其吸附CO2容量和CO2/N2选择性；技术层面上,构建H2O吸附、解离和新CO2吸附活性位形成的协同作用机制，设计调控纳米铁基/MOF材料结构，研制出中高湿度条件下具有更高CO2吸附容量和CO2/N2选择性的纳米铁基/MOF复合材料；以纳米铁基/MOF吸附材料为核心，研究高湿度环境下从混合气体中吸附分离捕获CO2过程，项目成果将为解决实际工况高湿条件下吸附分离捕获CO2这一难题提供新的理论和技术基础，项目研究具有重要科学研究价值。

针对吸附捕获CO2时，普遍存在混合气中水汽强竞争吸附导致CO2/N2分离效率急剧下降问题，本项目研制出纳米铁基/MOF复合材料并研究吸附分离CO2/N2/H2O机理。本项目制备了Fe3(μ3-O)(CH3COO)6和双金属的Fe2Co(μ3-O)(CH3COO)6簇铁基金属有机骨架材料，其具有非常优良的水汽稳定性。特别是，干燥条件下，PCN-250(Fe3)和PCN-250(Fe2Co)对CO2吸附量分别为1.177和1.321mmol/g；在相对湿度50%下，PCN-250(Fe3)和PCN-250(Fe2Co)对CO2吸附量分别为1.819和2.229mmol/g，相对干燥条件下分别提高54.5%和68.7%；在相对湿度90%下，PCN-250(Fe3)和PCN-250(Fe2Co)对CO2吸附量依然有所提高，分别为1.691和2.249mmol/g，相对干燥条件下分别提高了43.7%和70.2%。该材料不仅能克服水蒸气竞争吸附对绝大多数MOFs材料的负面效应，而且能把水蒸气竞争吸附转化成为正面效应的新型固体多孔吸附材料，使之能在中高湿度条件下更高效地吸附分离CO2 /N2。PCN-250(Fe3)和PCN-250(Fe2Co)是目前已报道的CO2吸附材料中，唯一可以既在低湿度又可以在高湿度条件下促进CO2 /N2分离的多孔材料。本项目成果为解决实际工况高湿条件下吸附分离捕获CO2这一难题提供新的理论和技术基础，项目研究具有重要科学研究价值。