Carson Fabian, Pascanu Vlad, Bermejo Gómez Antonio, Zhang Yi, Platero-Prats Ana E, Zou Xiaodong, Martín-Matute Belén
Berzelii Center EXSELENT on Porous Materials, Stockholm University, 106 91 Stockholm (Sweden).
Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm (Sweden).
Chemistry. 2015 Jul 20;21(30):10896-902. doi: 10.1002/chem.201500843. Epub 2015 Jun 23.
The chemical stability of metal-organic frameworks (MOFs) is a major factor preventing their use in industrial processes. Herein, it is shown that judicious choice of the base for the Suzuki-Miyaura cross-coupling reaction can avoid decomposition of the MOF catalyst Pd@MIL-101-NH2 (Cr). Four bases were compared for the reaction: K2 CO3 , KF, Cs2 CO3 and CsF. The carbonates were the most active and achieved excellent yields in shorter reaction times than the fluorides. However, powder XRD and N2 sorption measurements showed that the MOF catalyst was degraded when carbonates were used but remained crystalline and porous with the fluorides. XANES measurements revealed that the trimeric chromium cluster of Pd@MIL-101-NH2 (Cr) is still present in the degraded MOF. In addition, the different countercations of the base significantly affected the catalytic activity of the material. TEM revealed that after several catalytic runs many of the Pd nanoparticles (NPs) had migrated to the external surface of the MOF particles and formed larger aggregates. The Pd NPs were larger after catalysis with caesium bases compared to potassium bases.
金属有机框架材料（MOFs）的化学稳定性是阻碍其在工业过程中应用的主要因素。本文表明，明智地选择用于铃木-宫浦交叉偶联反应的碱可以避免MOF催化剂Pd@MIL-101-NH2（Cr）的分解。比较了该反应的四种碱：K2CO3、KF、Cs2CO3和CsF。碳酸盐的活性最高，与氟化物相比，在更短的反应时间内获得了优异的产率。然而，粉末XRD和N2吸附测量表明，使用碳酸盐时MOF催化剂会降解，但使用氟化物时仍保持结晶和多孔结构。XANES测量表明，Pd@MIL-101-NH2（Cr）的三聚体铬簇仍存在于降解后的MOF中。此外，碱的不同抗衡阳离子对材料的催化活性有显著影响。TEM显示，经过几次催化运行后，许多钯纳米颗粒（NPs）迁移到了MOF颗粒的外表面并形成了更大的聚集体。与钾碱相比，用铯碱催化后钯纳米颗粒更大。
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