Time-resolved control of nanoparticle integration in titanium-organic frameworks for enhanced catalytic performance.

Among the multiple applications of metal-organic frameworks (MOFs), their use as a porous platform for the support of metallic nanoparticles stands out for the possibility of integrating a good anchorage, that improves the stability of the catalyst, with the presence of a porous network that allows the diffusion of substrates and products. Here we introduce an alternative way to control the injection of Au nanoparticles at variable stages of nucleation of a titanium(iv) MOF crystal (MUV-10). This allows the analysis of the different modes of nanoparticle integration into the porous matrix as a function of the crystal formation stage and their correlation with the catalytic performance of the resulting composite.

Silver-Exchanged Zeolite Y Catalyzes a Selective Insertion of Carbenes into C-H and O-H Bonds.

Commercially available zeolite Y modulates the catalytic activity and selectivity of ultrasmall silver species during the Buchner reaction and the carbene addition to methylene and hydroxyl bonds, by simply exchanging the counter cations of the zeolite framework. The zeolite acts as a macroligand to tune the silver catalytic site, enabling the use of this cheap and recyclable solid catalyst for the in situ formation of carbenes from diazoacetate and selective insertion in different C-H (i.e.

Diastereoisomeric enrichment of 1,4-enediols and H-splitting inhibition on Pd-supported catalysts.

Pd-supported catalysts are fundamental tools in organic reactions involving H splitting. Here we show that 1,4-enediols enriched in one diastereoisomer are produced from the classical Pd-catalyzed semi-hydrogenation reaction with H, starting from the corresponding, widely available 1,4-diacetylenic diols. The semi-hydrogenation reaction proceeds concomitantly with the desymmetrization of the /racemic form of the enediol.

Ag(0) dimers within a thioether-functionalized MOF catalyze the CO to CH hydrogenation reaction.

Ultrasmall silver clusters in reduced state are difficult to synthesize since silver atoms tend to rapidly aggregate into bigger entities. Here, we show that dimers of reduced silver (Ag) are formed within the framework of a metal-organic framework provided with thioether arms in their walls (methioMOF), after reduction with NaBH of the corresponding Ag-methioMOF precursor. The resulting Ag-methioMOF catalyzes the methanation reaction of carbon dioxide (CO to CH hydrogenation reaction) under mild reaction conditions (1 atm CO, 4 atm H, 140 °C), with production rates much higher than Ag on alumina and even comparable to the state-of-the-art Ru on alumina catalyst (Ru-AlO) under these reaction conditions, according to literature results.

MOF-Triggered Synthesis of Subnanometer Ag Clusters and Fe Single Atoms: Heterogenization Led to Efficient and Synergetic One-Pot Catalytic Reactions.

The combination of well-defined Fe isolated single-metal atoms and Ag subnanometer metal clusters within the channels of a metal-organic framework (MOF) is reported and characterized by single-crystal X-ray diffraction for the first time. The resulting hybrid material, with the formula [Ag(Ag)Fe]@Na{Ni[Cu(Mempba)]}·63HO (), is capable of catalyzing the unprecedented direct conversion of styrene to phenylacetylene in one pot. In particular, ─which can easily be obtained in a gram scale─exhibits superior catalytic activity for the TEMPO-free oxidative cross-coupling of styrenes with phenyl sulfone to give vinyl sulfones in yields up to >99%, which are ultimately transformed, in situ, to the corresponding phenylacetylene product.

Highly Efficient MOF-Driven Silver Subnanometer Clusters for the Catalytic Buchner Ring Expansion Reaction.

The preparation of novel efficient catalysts─that could be applicable in industrially important chemical processes─has attracted great interest. Small subnanometer metal clusters can exhibit outstanding catalytic capabilities, and thus, research efforts have been devoted, recently, to synthesize novel catalysts bearing such active sites. Here, we report the gram-scale preparation of Ag subnanometer clusters within the channels of a highly crystalline three-dimensional anionic metal-organic framework, with the formula [Ag]@AgNa{Ni[Cu(Mempba)]}·48HO [Mempba = '-2,4,6-trimethyl-1,3-phenylenebis(oxamate)].

Parts-per-million of ruthenium catalyze the selective chain-walking reaction of terminal alkenes.

The chain-walking of terminal alkenes (also called migration or isomerization reaction) is currently carried out in industry with unselective and relatively costly processes, to give mixtures of alkenes with significant amounts of oligomerized, branched and reduced by-products. Here, it is shown that part-per-million amounts of a variety of commercially available and in-house made ruthenium compounds, supported or not, transform into an extremely active catalyst for the regioselective migration of terminal alkenes to internal positions, with yields and selectivity up to >99% and without any solvent, ligand, additive or protecting atmosphere required, but only heating at temperatures >150 °C. The resulting internal alkene can be prepared in kilogram quantities, ready to be used in nine different organic reactions without any further treatment.

A Biocompatible Aspartic-Decorated Metal-Organic Framework with Tubular Motif Degradable under Physiological Conditions.

Achieving a precise control of the final structure of metal-organic frameworks (MOFs) is necessary to obtain desired physical properties. Here, we describe how the use of a metalloligand design strategy and a judicious choice of ligands inspired from nature is a versatile approach to succeed in this challenging task. We report a new porous chiral MOF, with the formula Ca{Cu[(,)-aspartamox]}·160HO (), constructed from Cu and Ca ions and aspartic acid-decorated ligands, where biometal Cu ions are bridged by the carboxylate groups of aspartic acid moieties.

Soluble/MOF-Supported Palladium Single Atoms Catalyze the Ligand-, Additive-, and Solvent-Free Aerobic Oxidation of Benzyl Alcohols to Benzoic Acids.

Metal single-atom catalysts (SACs) promise great rewards in terms of metal atom efficiency. However, the requirement of particular conditions and supports for their synthesis, together with the need of solvents and additives for catalytic implementation, often precludes their use under industrially viable conditions. Here, we show that palladium single atoms are spontaneously formed after dissolving tiny amounts of palladium salts in neat benzyl alcohols, to catalyze their direct aerobic oxidation to benzoic acids without ligands, additives, or solvents.

Publisher Correction: Hydrolase-like catalysis and structural resolution of natural products by a metal-organic framework.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Hydrolase-like catalysis and structural resolution of natural products by a metal-organic framework.

The exact chemical structure of non-crystallising natural products is still one of the main challenges in Natural Sciences. Despite tremendous advances in total synthesis, the absolute structural determination of a myriad of natural products with very sensitive chemical functionalities remains undone. Here, we show that a metal-organic framework (MOF) with alcohol-containing arms and adsorbed water, enables selective hydrolysis of glycosyl bonds, supramolecular order with the so-formed chiral fragments and absolute determination of the organic structure by single-crystal X-ray crystallography in a single operation.

Bio-metal-organic frameworks for molecular recognition and sorbent extraction of hydrophilic vitamins followed by their determination using HPLC-UV.

A bio-metal-organic framework (bio-MOF) derived from the amino acid L-serine has been prepared in bulk form and evaluated as sorbent for the molecular recognition and extraction of B-vitamins. The functional pores of bio-MOF exhibit high amounts of hydroxyl groups jointly directing other supramolecular host-guest interactions thus providing the recognition of B-vitamins in fruit juices and energy drinks. Single-crystal X-ray diffraction studies reveal the specific B-vitamin binding sites and the existence of multiple hydrogen bonds between these target molecules and the framework.

Metal-Organic Frameworks as Chemical Nanoreactors: Synthesis and Stabilization of Catalytically Active Metal Species in Confined Spaces.

Since the advent of the first metal-organic frameworks (MOFs), we have witnessed an explosion of captivating architectures with exciting physicochemical properties and applications in a wide range of fields. This, in part, can be understood under the light of their rich host-guest chemistry and the possibility to use single-crystal X-ray diffraction (SC-XRD) as a basic characterization tool. Moreover, chemistry on preformed MOFs, applying recent developments in template-directed synthesis and postsynthetic methodologies (PSMs), has shown to be a powerful synthetic tool to (i) tailor MOFs channels of known topology via single-crystal to single-crystal (SC-SC) processes, (ii) impart higher degrees of complexity and heterogeneity within them, and most importantly, (iii) improve their capabilities toward applications with respect to the parent MOFs.

Metal-Organic Frameworks as Playgrounds for Reticulate Single-Molecule Magnets.

Achieving fine control on the structure of metal-organic frameworks (MOFs) is mandatory to obtain target physical properties. Herein, we present how the combination of a metalloligand approach and a postsynthetic method is a suitable and highly useful synthetic strategy to success on this extremely difficult task. First, a novel oxamato-based tetranuclear cobalt(III) compound with a tetrahedron-shaped geometry is used, for the first time, as the metalloligand toward calcium(II) metal ions to lead to a diamagnetic Ca-Co three-dimensional (3D) MOF ().

Multivariate Metal-Organic Frameworks for the Simultaneous Capture of Organic and Inorganic Contaminants from Water.

We report a new water-stable multivariate (MTV) metal-organic framework (MOF) prepared by combining two different oxamide-based metalloligands derived from the natural amino acids l-serine and l-methionine. This unique material features hexagonal channels decorated with two types of flexible and functional "arms" (-CHOH and -CHCHSCH) capable of enabling, synergistically, the simultaneous and efficient removal of both inorganic (heavy metals such as Hg, Pb, and Tl) and organic (dyes such as Pyronin Y, Auramine O, Brilliant green, and Methylene blue) contaminants, and, in addition, this MTV-MOF is completely reusable. Single-crystal X-ray diffraction measurements allowed solving the crystal structure of a host-guest adsorbate, containing both HgCl and Methylene blue, and offered unprecedented snapshots of this unique dual capture process.

Self-Assembly of Catalytically Active Supramolecular Coordination Compounds within Metal-Organic Frameworks.

Supramolecular coordination compounds (SCCs) represent the power of coordination chemistry methodologies to self-assemble discrete architectures with targeted properties. SCCs are generally synthesized in solution, with isolated fully coordinated metal atoms as structural nodes, thus severely limited as metal-based catalysts. Metal-organic frameworks (MOFs) show unique features to act as chemical nanoreactors for the in situ synthesis and stabilization of otherwise not accessible functional species.

Confined Pt Water Clusters in a MOF Catalyze the Low-Temperature Water-Gas Shift Reaction with both CO Oxygen Atoms Coming from Water.

The synthesis and reactivity of single metal atoms in a low-valence state bound to just water, rather than to organic ligands or surfaces, is a major experimental challenge. Herein, we show a gram-scale wet synthesis of Pt stabilized in a confined space by a crystallographically well-defined first water sphere, and with a second coordination sphere linked to a metal-organic framework (MOF) through electrostatic and H-bonding interactions. The role of the water cluster is not only isolating and stabilizing the Pt atoms, but also regulating the charge of the metal and the adsorption of reactants.

Lanthanide Discrimination with Hydroxyl-Decorated Flexible Metal-Organic Frameworks.

We report two new highly crystalline metal-organic frameworks (MOFs), derived from the natural amino acids serine (1) and threonine (2), featuring hexagonal channels densely decorated with hydroxyl groups belonging to the amino acid residues. Both 1 and 2 are capable of discriminating, via solid-phase extraction, a mixture of selected chloride salts of lanthanides on the basis of their size, chemical affinity, and/or the flexibility of the network. In addition, this discrimination follows a completely different trend for 1 and 2 because of the different locations of the hydroxyl groups in each compound, which is evocative of steric complementarity between the substrate and receptor.

Efficient Capture of Organic Dyes and Crystallographic Snapshots by a Highly Crystalline Amino-Acid-Derived Metal-Organic Framework.

The presence of residual organic dyes in water resources or wastewater treatment systems, derived mainly from effluents of different industries, is a major environmental problem with no easy solution. Herein, an ecofriendly, water-stable metal-organic framework was prepared from a derivative of the natural amino acid l-serine. Its functional channels are densely decorated with highly flexible l-serine residues bearing hydroxyl groups.

A post-synthetic approach triggers selective and reversible sulphur dioxide adsorption on a metal-organic framework.

We report the application of a post-synthetic solid-state cation-exchange process to afford a novel 3D MOF with hydrated barium cations hosted at pores able to trigger selective and reversible SO adsorption. Computational modelling supports the full reversibility of the adsorption process on the basis of weak supramolecular interactions between SO and coordinated water molecules.

Isolated Fe(III)-O Sites Catalyze the Hydrogenation of Acetylene in Ethylene Flows under Front-End Industrial Conditions.

The search for simple, earth-abundant, cheap, and nontoxic metal catalysts able to perform industrial hydrogenations is a topic of interest, transversal to many catalytic processes. Here, we show that isolated Fe-O sites on solids are able to dissociate and chemoselectively transfer H to acetylene in an industrial process. For that, a novel, robust, and highly crystalline metal-organic framework (MOF), embedding Fe-OH single sites within its pores, was prepared in multigram scale and used as an efficient catalyst for the hydrogenation of 1% acetylene in ethylene streams under front-end conditions.

Synthesis of Densely Packaged, Ultrasmall Pt Clusters within a Thioether-Functionalized MOF: Catalytic Activity in Industrial Reactions at Low Temperature.

The gram-scale synthesis, stabilization, and characterization of well-defined ultrasmall subnanometric catalytic clusters on solids is a challenge. The chemical synthesis and X-ray snapshots of Pt clusters, homogenously distributed and densely packaged within the channels of a metal-organic framework, is presented. This hybrid material catalyzes efficiently, and even more importantly from an economic and environmental viewpoint, at low temperature (25 to 140 °C), energetically costly industrial reactions in the gas phase such as HCN production, CO methanation, and alkene hydrogenations.

A novel oxalate-based three-dimensional coordination polymer showing magnetic ordering and high proton conductivity.

A novel three-dimensional (3D) coordination polymer with the formula (CNH)[MnCr(ox)]·5HO (2), where ox = oxalate and CNH = imidazolium cation, is reported. Single crystal X-ray diffraction reveals that this porous coordination polymer adopts a chiral three-dimensional quartz-like architecture, with the guest imidazolium cations and water molecules being hosted in its pores. This novel multifunctional material exhibits both a ferromagnetic ordering at T = 3.

The MOF-driven synthesis of supported palladium clusters with catalytic activity for carbene-mediated chemistry.

The development of catalysts able to assist industrially important chemical processes is a topic of high importance. In view of the catalytic capabilities of small metal clusters, research efforts are being focused on the synthesis of novel catalysts bearing such active sites. Here we report a heterogeneous catalyst consisting of Pd clusters with mixed-valence 0/+1 oxidation states, stabilized and homogeneously organized within the walls of a metal-organic framework (MOF).