CO fixation: cycloaddition of CO to epoxides using practical metal-free recyclable catalysts.

The conversion of CO into valuable chemicals is a crucial field of research. Cyclic organic carbonates have attracted great interest because they can be prepared under mild conditions and because of their structural versatility which enables a large variety of applications. Therefore, there is a need for potent and yet practical catalysts for the cycloaddition of CO to cyclic carbonates that are able to combine availability, low cost and an adequate performance.

Catalytic Strategies for the Cycloaddition of CO to Epoxides in Aqueous Media to Enhance the Activity and Recyclability of Molecular Organocatalysts.

The cycloaddition of CO to epoxides to afford versatile and useful cyclic carbonate compounds is a highly investigated method for the nonreductive upcycling of CO. One of the main focuses of the current research in this area is the discovery of readily available, sustainable, and inexpensive catalysts, and of catalytic methodologies that allow their seamless solvent-free recycling. Water, often regarded as an undesirable pollutant in the cycloaddition process, is progressively emerging as a helpful reaction component.

Revisiting the Potential of Group VI Inorganic Precatalysts for the Ethenolysis of Fatty Acids through a Mechanochemical Approach.

The utilization of biobased feedstocks to prepare useful compounds is a pivotal trend in current chemical research. Among a varied portfolio of naturally available starting materials, fatty acids are abundant, versatile substrates with multiple applications. In this context, the ethenolysis of unsaturated fatty acid esters such as methyl oleate is an atom-economical way to prepare functional C10 olefins with a biobased footprint.

Catalysts Prepared from Atomically Dispersed Ce(III) on MgO Rival Bulk Ceria for CO Oxidation.

Atomically dispersed cerium catalysts on an inert, crystalline MgO powder support were prepared by using both Ce(III) and Ce(IV) precursors. The materials were used as catalysts for CO oxidation in a once-through flow reactor and characterized by atomic-resolution scanning transmission electron microscopy, X-ray absorption near-edge structure spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed reduction, among other techniques, before and after catalysis. The most active catalysts, formed from the precursor incorporating Ce(III), displayed performance similar to that reported for bulk ceria under comparable conditions.

Heavy-element production in a compact object merger observed by JWST.

The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs), sources of high-frequency gravitational waves (GWs) and likely production sites for heavy-element nucleosynthesis by means of rapid neutron capture (the r-process). Here we present observations of the exceptionally bright GRB 230307A. We show that GRB 230307A belongs to the class of long-duration GRBs associated with compact object mergers and contains a kilonova similar to AT2017gfo, associated with the GW merger GW170817 (refs.

Samarium- and Ytterbium-Grafted Periodic Mesoporous Silica for Carbon Dioxide Capture and Conversion.

Immobilized coordination compounds of Lewis acidic metals are powerful catalytic components of systems for the cycloaddition of CO to epoxides that do not require sophisticated coordination frameworks to harness the metal center and modulate its activity. Surface organometallic chemistry (SOMC) is a valuable methodology to prepare well-defined and site-isolated surface complexes and coordination compounds on metal oxides, with ligand environments easily adjustable to a targeted catalytic reaction. In this work, the SOMC methodology is applied to prepare Sm, Yb, and Sm alkoxide surface complexes on periodic mesoporous (organo)silica of distinct pore symmetry/size for application in the CO cycloaddition reaction.

Organocatalytic Polymers from Affordable and Readily Available Building Blocks for the Cycloaddition of CO to Epoxides.

The catalytic cycloaddition of CO to epoxides to afford cyclic carbonates as useful monomers, intermediates, solvents, and additives is a continuously growing field of investigation as a way to carry out the atom-economic conversion of CO to value-added products. Metal-free organocatalytic compounds are attractive systems among various catalysts for such transformations because they are inexpensive, nontoxic, and readily available. Herein, we highlight and discuss key advances in the development of polymer-based organocatalytic materials that match these requirements of affordability and availability by considering their synthetic routes, the monomers, and the supports employed.

A very luminous jet from the disruption of a star by a massive black hole.

Tidal disruption events (TDEs) are bursts of electromagnetic energy that are released when supermassive black holes at the centres of galaxies violently disrupt a star that passes too close. TDEs provide a window through which to study accretion onto supermassive black holes; in some rare cases, this accretion leads to launching of a relativistic jet, but the necessary conditions are not fully understood. The best-studied jetted TDE so far is Swift J1644+57, which was discovered in γ-rays, but was too obscured by dust to be seen at optical wavelengths.

Hydrophobically-enhanced "on water" cycloaddition of CO to long-chain terminal epoxides.

Long-chain cyclic carbonates (LC-CC) are attractive building blocks and non-ionic surfactants. We demonstrate a convenient methodology to prepare LC-CC in miniemulsions of epoxide droplets in water. The pre-organization and confinement of the reagents from H-bond and hydrophobic interactions allow the target process to proceed at mild temperatures under atmospheric CO.

Simple Halogen-Free, Biobased Organic Salts Convert Glycidol to Glycerol Carbonate under Atmospheric CO Pressure.

Glycerol carbonate (GC) has emerged as an attractive synthetic target due to various promising technological applications. Among several viable strategies to produce GC from CO and glycerol and its derivatives, the cycloaddition of CO to glycidol represents an atom-economic an efficient strategy that can proceed via a halide-free manifold through a proton-shuttling mechanism. Here, it was shown that the synthesis of GC can be promoted by bio-based and readily available organic salts leading to quantitative GC formation under atmospheric CO pressure and moderate temperatures.

Microwave-Assisted Non-aqueous and Low-Temperature Synthesis of Titania and Niobium-Doped Titania Nanocrystals and Their Application in Halide Perovskite Solar Cells as Electron Transport Layers.

Undoped and Nb-doped TiO nanocrystals are prepared by a microwave-assisted non-aqueous sol-gel method based on a slow alkyl chloride elimination reaction between metal chlorides and benzyl alcohol. Sub-4 nm nanoparticles are grown under microwave irradiation at 80 °C in only 3 h with precise control of growth parameters and yield. The obtained nanocrystals could be conveniently used to cast compact TiO or Nb-doped TiO electron transport layers for application in formamidinium lead iodide-based photovoltaic devices.

Enhancing the Catalytic Performance of Group I, II Metal Halides in the Cycloaddition of CO to Epoxides under Atmospheric Conditions by Cooperation with Homogeneous and Heterogeneous Highly Nucleophilic Aminopyridines: Experimental and Theoretical Study.

Compared to metal-organic complexes and transition-metal halides, group I metal halides are attractive catalysts for the crucial cycloaddition reaction of CO to epoxides as they are ubiquitously available and inexpensive, have a low molecular weight, and are not based on (potentially) endangered metals, especially for the case of sodium and potassium. Nevertheless, given their low intrinsic catalytic efficiency, they require the assistance of additional catalytic moieties. In this work, we show that by exploiting the high nucleophilicity of opportunely designed aminopyridines, catalytic systems based on alkaline metals can be formed, which allow the cycloaddition of CO to epoxides to proceed under atmospheric pressure at moderate temperatures.

Dataset for the synthesis and application of single-component heterogeneous catalysts based on zinc and tin for the cycloaddition of pure, diluted, and impure CO to epoxides under mild conditions.

The cycloaddition of CO to epoxides under mild conditions is a growing field of research and a viable strategy to recycle CO in the form of cyclic carbonates as useful intermediates, solvents, and additives. This target requires readily accessible and recyclable catalysts whose synthesis does not involve expensive monomers, multistep procedures, coupling reagents, etc. Additionally, the catalysts should be active under atmospheric pressure and tolerate impurities such as methane and HS.

The Comparison between Single Atom Catalysis and Surface Organometallic Catalysis.

Single atom catalysis (SAC) is a recent discipline of heterogeneous catalysis for which a single atom on a surface is able to carry out various catalytic reactions. A kind of revolution in heterogeneous catalysis by metals for which it was assumed that specific sites or defects of a nanoparticle were necessary to activate substrates in catalytic reactions. In another extreme of the spectrum, surface organometallic chemistry (SOMC), and, by extension, surface organometallic catalysis (SOMCat), have demonstrated that single atoms on a surface, but this time with specific ligands, could lead to a more predictive approach in heterogeneous catalysis.

Polymers Based on Cyclic Carbonates as Trait d'Union Between Polymer Chemistry and Sustainable CO Utilization.

Given the large amount of anthropogenic CO emissions, it is advantageous to use CO as feedstock for the fabrication of everyday products, such as fuels and materials. An attractive way to use CO in the synthesis of polymers is by the formation of five-membered cyclic organic carbonate monomers (5CCs). The sustainability of this synthetic approach is increased by using scaffolds prepared from renewable resources.

Surface organometallic chemistry in heterogeneous catalysis.

The broad challenges of energy and environment have become a main focus of research efforts to develop more active and selective catalytic systems for key chemical transformations. Surface organometallic chemistry (SOMC) is an established concept, associated with specific tools, for the design, preparation and characterization of well-defined single-site catalysts. The objective is to enter a catalytic cycle through a presumed catalytic intermediate prepared from organometallic or coordination compounds to generate well defined surface organometallic fragments (SOMFs) or surface coordination fragments (SCFs).

Current advances in the catalytic conversion of carbon dioxide by molecular catalysts: an update.

Due to the high emissions of CO2 and the related environmental impact, the chemical transformation of CO2 to useful industrially relevant products or their precursor is of significant interest. Recycling CO2 as a building block for the synthesis of chemicals may not only reduce further emission by at least replacing oil-derived feedstocks, but also provide the advantages of CO2 as an inexpensive, non-toxic and easily available substrate. The catalytic conversion of CO2 into small, useful molecules such as carbonates, methyl amines, methanol, formic acid, etc.

Physico-chemical investigation of ZnS thin-film deposited from ligand-free nanocrystals synthesized by non-hydrolytic thio-sol-gel.

Ultra-small and monodispersed zinc sulfide nanocrystals (NCs) (d ≤ 3 nm) have been prepared without the use of any surfactants by a synthetic route using benzyl mercaptan as a source of sulfur. The prepared NCs are dispersible in highly polar solvents and display the capability to closely pack-up in a bulky film. The NCs were characterized by TEM, XRD and UV-vis optical absorption as well as by steady-state and time-resolved photoluminescence (PL) spectroscopies.

SOMC grafting of vanadium oxytriisopropoxide (VO(O Pr)) on dehydroxylated silica; analysis of surface complexes and thermal restructuring mechanism.

Vanadium oxytriisopropoxide (VO(O Pr)), 1, was grafted on highly dehydroxylated silica (SiO: aerosil silica treated at 700 °C under high vacuum) to generate compound 2 following the concepts and methodology of surface organometallic chemistry (SOMC). The resulting compound was analyzed by elemental analysis, FT-IR, H, C and V solid state (SS) NMR, Raman and EPR spectroscopies. The grafting reaction of 1 to generate 2 was found to lead to the formation of a monopodal surface complex [([triple bond, length as m-dash]Si-O-)V(O)(O Pr)], 2m, as well as bipodal [([triple bond, length as m-dash]Si-O-)V(O)(O Pr)], 2b, formed along with ([triple bond, length as m-dash]Si-O- Pr) moieties as an effect of the classical rearrangement of 2m with strained siloxane bridges.

Clean chlorination of silica surfaces by a single-site substitution approach.

A chlorination method for the selective substitution of well-defined isolated silanol groups of the silica surface has been developed using the catalytic Appel reaction. Spectroscopic analysis, complemented by elemental microanalysis studies, reveals that a quantitative chlorination could be achieved with highly dehydroxylated silica materials that exclusively possess non-hydrogen bonded silanol groups. The employed method did not leave any carbon or phosphorus residue on the silica surface and can be regarded as a promising tool for the future functionalization of metal oxide surfaces.

SOMC-Designed Silica Supported Tungsten Oxo Imidazolin-2-iminato Methyl Precatalyst for Olefin Metathesis Reactions.

Synthesis, structure, and olefin metathesis activity of a surface complex [(≡Si-O-)W(═O)(CH)-ImN] (4) (Im = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-iminato) supported on silica by a surface organometallic chemistry (SOMC) approach are reported. The reaction of N-silylated 2-iminoimidazoline with tungsten(VI) oxytetrachloride generated the tungsten oxo imidazolin-2-iminato chloride complex [ImNW(═O)Cl] (2). This was grafted on partially dehydroxylated silica pretreated at 700 °C (SiO) to afford a well-defined monopodal surface complex [(≡Si-O-)W(═O)Cl-ImN] (3).

Binding of molecular oxygen by an artificial heme analogue: investigation on the formation of an Fe-tetracarbene superoxo complex.

The dioxygen reactivity of a cyclic iron(ii) tetra-NHC-complex (NHC: N-heterocyclic carbene) is investigated. Divergent oxidation behavior is observed depending on the choice of the solvent (acetonitrile or acetone). In the first case, exposure to molecular oxygen leads to an oxygen free Fe(iii) whereas in the latter case an oxide bridged Fe(iii) dimer is formed.

Controlling the hydrogenolysis of silica-supported tungsten pentamethyl leads to a class of highly electron deficient partially alkylated metal hydrides.

The well-defined single-site silica-supported tungsten complex [([triple bond, length as m-dash]Si-O-)W(Me)], , is an excellent precatalyst for alkane metathesis. The unique structure of allows the synthesis of unprecedented tungsten hydrido methyl surface complexes a controlled hydrogenolysis. Specifically, in the presence of molecular hydrogen, is quickly transformed at -78 °C into a partially alkylated tungsten hydride, , as characterized by H solid-state NMR and IR spectroscopies.

Cooperative Effect of Monopodal Silica-Supported Niobium Complex Pairs Enhancing Catalytic Cyclic Carbonate Production.

Recent discoveries highlighted the activity and the intriguing mechanistic features of NbCl5 as a molecular catalyst for the cycloaddition of CO2 and epoxides under ambient conditions. This has inspired the preparation of novel silica-supported Nb species by reacting a molecular niobium precursor, [NbCl5·OEt2], with silica dehydroxylated at 700 °C (SiO(2-700)) or at 200 °C (SiO(2-200)) to generate diverse surface complexes. The product of the reaction between SiO(2-700) and [NbCl5·OEt2] was identified as a monopodal supported surface species, [≡SiONbCl4·OEt2] (1a).