title: Sustainable catalysis: rational Pd loading on MIL-101Cr-NH2 for more efficient and recyclable Suzuki-Miyaura reactions.
abstract: Palladium nanoparticles have been immobilized into an amino-functionalized metal-organic framework (MOF), MIL-101Cr-NH2, to form Pd@MIL-101Cr-NH2. Four materials with different loadings of palladium have been prepared (denoted as 4-, 8-, 12-, and 16 wt%Pd@MIL-101Cr-NH2). The effects of catalyst loading and the size and distribution of the Pd nanoparticles on the catalytic performance have been studied. The catalysts were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), N2-sorption isotherms, elemental analysis, and thermogravimetric analysis (TGA). To better characterize the palladium nanoparticles and their distribution in MIL-101Cr-NH2, electron tomography was employed to reconstruct the 3D volume of 8 wt%Pd@MIL-101Cr-NH2 particles. The pair distribution functions (PDFs) of the samples were extracted from total scattering experiments using high-energy X-rays (60 keV). The catalytic activity of the four MOF materials with different loadings of palladium nanoparticles was studied in the Suzuki-Miyaura cross-coupling reaction. The best catalytic performance was obtained with the MOF that contained 8 wt% palladium nanoparticles. The metallic palladium nanoparticles were homogeneously distributed, with an average size of 2.6 nm. Excellent yields were obtained for a wide scope of substrates under remarkably mild conditions (water, aerobic conditions, room temperature, catalyst loading as low as 0.15 mol%). The material can be recycled at least 10 times without alteration of its catalytic properties.
authors.affiliation: Berzelii Center EXSELENT on Porous Materials, Stockholm University, SE-10691 Stockholm (Sweden); Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm (Sweden).
authors.forename: Vlad
authors.initials: V
authors.lastname: Pascanu
authors.forename: Qingxia
authors.initials: Q
authors.lastname: Yao
authors.forename: Antonio
authors.initials: A
authors.lastname: Bermejo Gómez
authors.forename: Mikaela
authors.initials: M
authors.lastname: Gustafsson
authors.forename: Yifeng
authors.initials: Y
authors.lastname: Yun
authors.forename: Wei
authors.initials: W
authors.lastname: Wan
authors.forename: Louise
authors.initials: L
authors.lastname: Samain
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zou
authors.forename: Belén
authors.initials: B
authors.lastname: Martín-Matute
keywords: cross-coupling; heterogeneous catalysts; metal-organic frameworks; nanoparticles; palladium