National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.
University of Nova Gorica, Vipavska 13, 5000 Nova Gorica, Slovenia.
ACS Appl Mater Interfaces. 2023 Apr 12;15(14):18354-18361. doi: 10.1021/acsami.3c01796. Epub 2023 Mar 30.
Currently, metal-organic framework (MOF)-polymer composites are attracting great interest as a step forward in making MOFs a useful material for industrially relevant applications. However, most of the research is engaged with finding promising MOF/polymer pairs and less with the synthetic methods by which these materials are then combined, albeit hybridization has a significant impact on the properties of the new composite macrostructure. Thus, the focus of this work is on the innovative hybridization of MOFs and polymerized high internal phase emulsions (polyHIPEs), two classes of materials that exhibit porosity at different length scales. The main thrust is the in situ secondary recrystallization, i.e., growth of MOFs from metal oxides previously fixed in polyHIPEs by the Pickering HIPE-templating, and further structure-function study of composites through the CO capture behavior. The combination of Pickering HIPE polymerization and secondary recrystallization at the metal oxide-polymer interface proved advantageous, as MOF-74 isostructures based on different metal cations (M = Mg, Co, or Zn) could be successfully shaped in the polyHIPEs' macropores without affecting the properties of the individual components. The successful hybridization resulted in highly porous, co-continuous MOF-74-polyHIPE composite monoliths forming an architectural hierarchy with pronounced macro-microporosity, in which the MOF microporosity is almost completely accessible for gases, i.e., about 87% of the micropores, and the monoliths exhibit excellent mechanical stability. The well-structured porous architecture of the composites showed superior CO capture performance compared to the parent MOF-74 powders. Both adsorption and desorption kinetics are significantly faster for composites. Regeneration by temperature swing adsorption recovers about 88% of the total adsorption capacity of the composite, while it is lower for the parent MOF-74 powders (about 75%). Finally, the composites exhibit about 30% improvement in CO uptake under working conditions compared to the parent MOF-74 powders, and some of the composites are able to retain 99% of the original adsorption capacity after five adsorption/desorption cycles.
目前，金属-有机骨架（MOF）-聚合物复合材料作为将 MOF 应用于具有工业相关应用的有用材料的一大进步，正引起极大的兴趣。然而，大多数研究都致力于寻找有前途的 MOF/聚合物对，而对这些材料的合成方法研究较少，尽管杂化对新复合宏观结构的性质有重大影响。因此，这项工作的重点是 MOF 和聚合高内相乳液（polyHIPE）的创新性杂化，这两类材料在不同的长度尺度上表现出多孔性。主要目的是 MOF 从以前通过 Pickering HIPE 模板固定在 polyHIPE 中的金属氧化物的原位二次再结晶，即 MOF 的二次再结晶，以及通过 CO 捕获行为对复合材料进行进一步的结构功能研究。Pickering HIPE 聚合与金属氧化物-聚合物界面的二次再结晶相结合具有优势，因为可以在 polyHIPE 的大孔中成功成型基于不同金属阳离子（M = Mg、Co 或 Zn）的 MOF-74 同构物，而不会影响各个成分的性质。成功的杂化导致高度多孔、共连续的 MOF-74-polyHIPE 复合整体式单块形成具有明显的宏观-微孔结构的分级结构，其中 MOF 微孔几乎完全可用于气体，即大约 87%的微孔，并且整体式单块表现出优异的机械稳定性。与母体 MOF-74 粉末相比，复合材料的结构良好的多孔结构表现出优异的 CO 捕获性能。复合材料的吸附和脱附动力学都明显更快。通过温度摆动吸附再生可回收约 88%的复合材料的总吸附容量，而母体 MOF-74 粉末则较低（约 75%）。最后，与母体 MOF-74 粉末相比，在工作条件下，复合材料的 CO 吸收量提高了约 30%，并且一些复合材料在五个吸附/脱附循环后仍能保留 99%的原始吸附容量。
