Influence of the Base on Pd@MIL-101-NH2(Cr) as Catalyst for the Suzuki-Miyaura Cross-Coupling Reaction

• Published in: Chemistry : a European journal Vol. 21; no. 30; pp. 10896 - 10902
• Main Authors: Carson, Fabian, Pascanu, Vlad, Bermejo Gómez, Antonio, Zhang, Yi, Platero-Prats, Ana E, Zou, Xiaodong, Martín-Matute, Belén
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 20.07.2015; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Chemistry; cross-coupling; Fluorides; heterogeneous catalysis; metal-organic frameworks; nanoparticles; Organic Chemistry; organisk kemi; palladium; cross-coupling; palladium; nanoparticles; heterogeneous catalysis; metal-organic frameworks
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.201500843

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: K2CO3, KF, Cs2CO3 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. The bases of catalysis: The heterogeneous metal–organic framework (MOF) catalyst Pd@MIL‐101‐NH2(Cr) is highly affected by the base during the Suzuki–Miyaura cross‐coupling reaction. The base influences the catalytic activity, crystallinity, porosity and palladium distribution of the material (see figure). Use of carbonates as the base leads to MOF degradation, whereas use of fluorides preserves the MOF structure.