Bueken Bart, Van Velthoven Niels, Willhammar Tom, Stassin Timothée, Stassen Ivo, Keen David A, Baron Gino V, Denayer Joeri F M, Ameloot Rob, Bals Sara, De Vos Dirk, Bennett Thomas D
Centre for Surface Chemistry and Catalysis , Department of Microbial and Molecular Systems (M2S) , KU Leuven , Celestijnenlaan 200F p.o. box 2461 , 3001 Leuven , Belgium . Email:
EMAT , University of Antwerp , Groenenborgerlaan 171 , 2020 Antwerp , Belgium.
Chem Sci. 2017 May 1;8(5):3939-3948. doi: 10.1039/c6sc05602d. Epub 2017 Mar 23.
The ability of metal-organic frameworks (MOFs) to gelate under specific synthetic conditions opens up new opportunities in the preparation and shaping of hierarchically porous MOF monoliths, which could be directly implemented for catalytic and adsorptive applications. In this work, we present the first examples of xero- or aerogel monoliths consisting solely of nanoparticles of several prototypical Zr-based MOFs: UiO-66-X (X = H, NH, NO, (OH)), UiO-67, MOF-801, MOF-808 and NU-1000. High reactant and water concentrations during synthesis were observed to induce the formation of gels, which were converted to monolithic materials by drying in air or supercritical CO. Electron microscopy, combined with N physisorption experiments, was used to show that irregular nanoparticle packing leads to pure MOF monoliths with hierarchical pore systems, featuring both intraparticle micropores and interparticle mesopores. Finally, UiO-66 gels were shaped into monolithic spheres of 600 μm diameter using an oil-drop method, creating promising candidates for packed-bed catalytic or adsorptive applications, where hierarchical pore systems can greatly mitigate mass transfer limitations.
金属有机框架材料（MOFs）在特定合成条件下形成凝胶的能力，为制备和塑造具有分级孔隙结构的MOF整体材料开辟了新机遇，这些整体材料可直接用于催化和吸附应用。在本工作中，我们展示了首个仅由几种典型锆基金属有机框架材料（UiO-66-X（X = H、NH、NO、(OH)）、UiO-67、MOF-801、MOF-808和NU-1000）的纳米颗粒组成的干凝胶或气凝胶整体材料实例。合成过程中观察到高反应物浓度和高水浓度会诱导凝胶形成，通过在空气中干燥或超临界CO2干燥，这些凝胶被转化为整体材料。结合N2物理吸附实验的电子显微镜用于表明不规则的纳米颗粒堆积导致具有分级孔隙系统的纯MOF整体材料，其具有颗粒内微孔和颗粒间介孔。最后，使用油滴法将UiO-66凝胶成型为直径600μm的整体球体，为填充床催化或吸附应用创造了有前景的候选材料，其中分级孔隙系统可极大地减轻传质限制。
