铪金属-有机骨架材料的孔尺寸调控及其吸附性能

摘要

利用三种不同长度的有机配体--反丁烯二酸（H2FUM）、对苯二甲酸（H2BDC）和联苯二甲酸（H2BPDC），合成了一系列具有不同孔尺寸的新型铪（Hf）金属-有机骨架（MOF）材料（Hf-FUM、Hf-BDC 和 Hf-BPDC），并考察了 CO2、N2和 CH4三种气体在这些材料中吸附分离行为。研究结果表明，这三种材料具有和 UiO-66(Zr)相同的拓扑结构，且具有很好的热稳定性。Hf-FUM和Hf-BDC的结构在水中能够保持稳定，而Hf-BPDC在水中会发生降解。同时，具有最小孔尺寸的Hf-FUM材料对CO2/N2以及CO2/CH4体系具有最好的分离性能。这为以后设计用于CO2分离的新型纳微结构材料提供了参考依据。separation of CO2/N2and CO2/CH4 systems were also investigated. It is found that Hf-FUM with the smallest pore size possesses the highest adsorption selectivity for CO2 over N2and CH4. This is the first study on the performance of Hf-based MOFs for gas separation, and the knowledge obtained in this work provides a foundation for the design of new nanoporous materials towards CO2 capture from various gas mixtures.%By incorporating three organic carboxylic acids with different lengths, fumaric (FUM), 1,4-benzene- dicarboxylate (BDC) and 4,4′-biphenyl-dicarboxylate (BPDC) acids, three novel Hf-based metal-organic frameworks (MOFs), Hf-FUM, Hf-BDC and Hf-BPDC, were synthesized using a solvothermal method combined with conventional electric heating. These MOFs were characterized by various experimental techniques including PXRD, N2 adsorption, TG and SEM. Moreover, the stabilities of these materials were examined by soaking the samples in water. The PXRD results reveal that all of these Hf-based MOFs have a topology similar to that of UiO-66(Zr), and Hf-FUM is stable up to 400°C while Hf-BDC and Hf-BPDC remain stable at 500°C. The structures of Hf-FUM and Hf-BDC are water-resistant, while that of Hf-BPDC will decompose after water treatment. On the basis of the adsorption isotherms of CO2, N2 and CH4 at 298 K, the effect of pore size on the separation of CO2/N2 and CO2/CH4 systems were also investigated. It is found that Hf-FUM with the smallest pore size possesses the highest adsorption selectivity for CO2 over N2 and CH4. This is the first study on the performance of Hf-based MOFs for gas separation, and the knowledge obtained in this work provides a foundation for the design of new nanoporous materials towards CO2 capture from various gas mixtures.