Oxidative carbonylation of -protected indoles by Rh(III)-zeolites.

The oxidative carbonylation of -protected indoles was investigated to directly synthesize indole-3-carboxylic acids. Using Rh(III)-zeolites as heterogeneous catalysts, the single-site Rh-species reach unprecedented activities (>100 turnovers), while the metal is readily recovered after reaction. X-ray absorption spectroscopy (XAS) provided evidence for site-isolation of Rh(III) species on the zeolite.

Cu-α-diimine Compounds Encapsulated in Porous Materials as Catalysts for Electrophilic Amination of Aromatic C-H Bonds.

Electrophilic amination has emerged as a more environmentally benign approach to construct arene C-N bonds. However, heterogeneous catalysts remain largely unexplored in this area, even though their use could facilitate product purification and catalyst recovery. Here we investigate strategies to heterogenize a Cu(2,2'-bipyridine) catalyst for the amination of arenes lacking a directing group with hydroxylamine--sulfonic acid (HOSA).

Ru-Bipyridine Entrapped in the Supercages of EMC-1 Faujasite as Catalyst for the Trifluoromethylation of Arenes.

Trifluoromethyl (CF) groups are versatile structural motifs especially in the field of agrochemicals and pharmaceuticals. However, current trifluoromethylation reactions are generally associated with stoichiometric amounts of transition metals/metal oxidants, homogeneous catalysts, high temperatures, and expensive trifluoromethylating agents. In this work, the homogeneous photocatalyst Ru(bipy) is entrapped in the pores of a faujasite support (EMC-1) via a "ship-in-a-bottle" strategy.

Heterogeneous Single-Site Catalysts for C-H Activation Reactions: Pd(II)-Loaded S,O-Functionalized Metal Oxide-Bisphosphonates.

Heterogeneous single-site catalysts contain spatially isolated, well-defined active sites. This allows not only their easy recovery by solid-liquid separation but also the detailed active site design similar to homogeneous catalysts. Here, heterogeneous Pd(II) single-site catalysts were assembled, based on mesoporous metal oxide-bisphosphonate materials as supports.

C2-H Arylation of Indoles Catalyzed by Palladium-Containing Metal-Organic-Framework in γ-Valerolactone.

An efficient and selective procedure was developed for the direct C2-H arylation of indoles using a Pd-loaded metal-organic framework (MOF) as a heterogeneous catalyst and the nontoxic biomass-derived solvent γ-valerolactone (GVL) as a reaction medium. The developed method allows for excellent yields and C-2 selectivity to be achieved and tolerates various substituents on the indole scaffold. The established conditions ensure the stability of the catalyst as well as recoverability, reusability, and low metal leaching into the solution.

Modulator-Mediated Functionalization of MOF-808 as a Platform Tool to Create High-Performance Mixed-Matrix Membranes.

Modulator-mediated functionalization (MoFu) is introduced as a new and versatile platform tool to improve the separation performance of metal-organic framework (MOF)-based membranes, exemplified here by the creation of mixed-matrix membranes (MMMs) with enhanced CO separation efficiency. The unique structure of MOF-808 allows incorporation of CO-philic modulators in the MOF framework during a one-pot synthesis procedure in water, thus creating a straightforward way to functionalize both MOF and corresponding MMM. As a proof of concept, a series of fluorinated carboxylic acids [trifluoroacetic acid (TFA), pentafluoropropionic acid (PFPA), and heptafluorobutyric acid (HFBA)] and nonfluorinated alkyl carboxylic acids (acetic acid (AA), propionic acid (PA), and butyric acid (BA)) were used as a modulator during MOF-808 synthesis.

Expanding the Variety of Zirconium-based Inorganic Building Units for Metal-Organic Frameworks.

Two new zirconium-based metal-organic frameworks with the composition [Zr O (OH) (OAc) (BDC) ] (CAU-26) and [Zr O (OH) (OAc) (BDC) ] (CAU-27) are reported, which were synthesized from acetic acid, a rarely utilized but green and sustainable solvent (BDC : 1,4-benzenedicarboxylate). Structure determination aided by automated electron diffraction tomography revealed that CAU-26 is composed of layers of well-known {Zr O } clusters interconnected by terephthalate ions. In contrast CAU-27 exhibits a three-dimensional structure with a so far unknown type of one-dimensional inorganic building unit (IBU), which can be rationalized as condensed polyhedron-sharing chains of {Zr O } clusters.

Single-site metal-organic framework catalysts for the oxidative coupling of arenes C-H/C-H activation.

C-H activation reactions are generally associated with relatively low turnover numbers (TONs) and high catalyst concentrations due to a combination of low catalyst stability and activity, highlighting the need for recyclable heterogeneous catalysts with stable single-atom active sites. In this work, several palladium loaded metal-organic frameworks (MOFs) were tested as single-site catalysts for the oxidative coupling of arenes (-xylene) C-H/C-H activation. Isolation of the palladium active sites on the MOF supports reduced Pd(0) aggregate formation and thus catalyst deactivation, resulting in higher turnover numbers (TONs) compared to the homogeneous benchmark reaction.

Gel-based morphological design of zirconium metal-organic frameworks.

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.