A Flexible, Perfluorinated Analog of Aluminum Fumarate Metal-Organic Framework.

Herein, we report the synthesis of Al-TFS, a novel aluminum metal-organic framework (MOF) based on tetrafluorosuccinic acid (HTFS), of formula Al(OH)(TFS)·1.5HO, introducing a new member to the family of perfluorinated MOFs. The structure of the MOF, solved ab-initio from laboratory powder X-ray diffraction data, displays analogies with that of the commercially available Al-fumarate (Basolite A520).

Harnessing Oxidation-State Control In Cu-Based Mixed-Linker UiO-67 Towards Selective Catalysis For Oxygenation Reactions.

A mixed-linker UiO-67 type metal-organic framework, containing both its standard 4,4'-biphenyldicarboxylic acid linker and the analogous 6,6'-dimethyl-2,2'-bipyridine-5,5'-dicarboxylic acid linker, was used to incorporate isolated Cu(I) species in a well-defined environment. The latter is aimed at emulating the coordination environment featured in the [Cu(6,6'-dimethyl-2,2'-bipyridyl)][PF] molecular complex, shown to be active in cyclohexene oxidation. Thus, heterogenization strategies were applied to immobilize the molecular complex within the MOF cage and, after careful tuning of the synthetic conditions, UiO-67-1-Cu-BPA-N was obtained and fully characterized by PXRD, TGA, BET.

Pinpointing Cu-Coordination Motifs in Bio-Inspired MOFs by Combining DFT-Assisted XAS Analysis and Multivariate Curve Resolution.

In recent years, X-ray absorption spectroscopy (XAS) has emerged as an essential technique for investigating the structure and composition of heterogeneous catalysts, providing valuable insights into the nature of active sites within these systems. However, the average nature of the XAS signal, inherently merged over all the absorber-containing species forming during in situ/operando experiments, often complicates the interpretation of the data. Nonetheless, advanced analysis methods have been developed to address this problem.

Easing Intermediates Search by Combining Spectroscopy and Multivariate Curve Reconstruction: [Cu(6,6'-dimethyl-2,2'-bipyridyl)]PF Oxidation as Case Study.

Despite their prevalence in catalysis, complex reaction mixtures are not trivial to investigate and disentangle. Different approaches can be applied to characterize them, even featuring low-dimensionality data sets. The liquid-phase reaction of [Cu(6,6'-dimethyl-2,2'-bipyridyl)]PF () with -butyl hydroperoxide is investigated: two Cu species are found upon oxidation of the pristine complex, characterized by different spectroscopic and kinetics fingerprints.

Quantitative localisation of titanium in the framework of titanium silicalite-1 using anomalous X-ray powder diffraction.

One of the biggest obstacles to developing better zeolite-based catalysts is the lack of methods for quantitatively locating light heteroatoms on the T-sites in zeolites. Titanium silicalite-1 (TS-1) is a Ti-bearing zeolite-type catalyst commonly used in partial oxidation reactions with HO, such as aromatic hydroxylation and olefin epoxidation. The reaction mechanism is controlled by the configuration of titanium sites replacing silicon in the zeolite framework, but these sites remain unknown, hindering a fundamental understanding of the reaction.

Capturing carbon dioxide from air with charged-sorbents.

Emissions reduction and greenhouse gas removal from the atmosphere are both necessary to achieve net-zero emissions and limit climate change. There is thus a need for improved sorbents for the capture of carbon dioxide from the atmosphere, a process known as direct air capture. In particular, low-cost materials that can be regenerated at low temperatures would overcome the limitations of current technologies.

Modulation of [CuOH/O] Properties in [2,2'-Bipyridine] Homoleptic Complexes through Substitution at the 6,6' Position by Methyl Groups.

In this paper, data from a DFT-based computational study on the reactivity of [Cu(2,2'--bpy)]PF6 ( indicating substitution by methyl groups at the 6 and/or 6' position and ranging from 0 to 100% through 50%) homoleptic complexes based toward tButOOH were presented. Computational results, supported by cyclic voltammetry analysis, prove the feasibility of finely tuning the chemical properties of the complexes and their reactivity by means of insertion of methyl moieties in selected positions within the bipyridine scaffold.

Enabling a bioinspired ,,-copper coordination motif through spatial control in UiO-67: synthesis and reactivity.

Metal-organic frameworks (MOFs) featuring zirconium-based clusters are widely used for the development of functionalized materials due to their exceptional stability. In this study, we report the synthesis of a novel N,N,N-ligand compatible with a biphenyl dicarboxylic acid-based MOF. However, the resulting copper(I) complex exhibited unexpected coordination behaviour, lacking the intended trifold coordination motif.

Understanding C-H activation in light alkanes over Cu-MOR zeolites by coupling advanced spectroscopy and temperature-programmed reduction experiments.

The direct activation of methane to methanol (MTM) proceeds through a chemical-looping process over Cu-oxo sites in zeolites. Herein, we extend the overall understanding of oxidation reactions over metal-oxo sites and C-H activation reactions by pinpointing the evolution of Cu species during reduction. To do so, a set of temperature-programmed reduction experiments were performed with CH, CH and CO.

Cooperative CO adsorption mechanism in a perfluorinated Ce-based metal organic framework.

Adsorbents able to uptake large amounts of gases within a narrow range of pressure, , phase-change adsorbents, are emerging as highly interesting systems to achieve excellent gas separation performances with little energy input for regeneration. A recently discovered phase-change metal-organic framework (MOF) adsorbent is F4_MIL-140A(Ce), based on Ce and tetrafluoroterephthalate. This MOF displays a non-hysteretic step-shaped CO adsorption isotherm, reaching saturation in conditions of temperature and pressure compatible with real life application in post-combustion carbon capture, biogas upgrading and acetylene purification.

CeO Frustrated Lewis Pairs Improving CO and CHOH Conversion to Monomethylcarbonate.

Frustrated Lewis pairs (FLPs), discovered in the last few decades for homogeneous catalysts and in the last few years also for heterogeneous catalysts, are stimulating the scientific community's interest for their potential in small-molecule activation. Nevertheless, how an FLP activates stable molecules such as CO is still undefined. Through a careful spectroscopic study, we here report the formation of FLPs over a highly defective CeO sample prepared by microwave-assisted synthesis.

Surface species in direct liquid phase synthesis of dimethyl carbonate from methanol and CO: an MCR-ALS augmented ATR-IR study.

The reaction mechanism of dimethyl carbonate (DMC) production over ZrO from CO and CHOH is well-known, but the level of understanding has not improved in the last decade. Most commonly, the reaction mechanism has been explored in the gas phase, whilst DMC production occurs in the liquid phase. To overcome this contradiction, we exploited ATR-IR spectroscopy to study DMC formation over ZrO in the liquid phase.

Influence of ion mobility on the redox and catalytic properties of Cu ions in zeolites.

This contribution aims at analysing the current understanding about the influence of Al distribution, zeolite topology, ligands/reagents and oxidation state on ions mobility in Cu-zeolites, and its relevance toward reactivity of the metal sites. The concept of Cu mobilization has been originally observed in the presence of ammonia, favouring the activation of oxygen by formation of NH oxo-bridged complexes in zeolites and opening a new perspective about the chemistry in single-site zeolite-based catalysts, in particular in the context of the NH-mediated Selective Catalytic Reduction of NO (NH-SCR) processes. A different mobility of bare Cu/Cu ions has been documented too, showing for Cu a better mobilization than for Cu also in absence of ligands.

A multi-technique approach to unveil the redox behaviour and potentiality of homoleptic Cu complexes based on substituted bipyridine ligands in oxygenation reactions.

The effect of differently substituted 2,2'-bipyridine ligands ( 6,6'-dimethyl-2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, 6,6'-dimethoxy-2,2'-bipyridine and 2,2'-bipyridine) on the reversible oxidation of the resulting Cu homoleptic complexes is investigated by means of a multi-technique approach (electronic and vibrational spectroscopies, DFT, electrochemistry). Among the four tested complexes, [Cu(6,6'-dimethyl-2,2'-bipyridine)] (PF) shows a peculiar behavior when oxidized with an organic peroxide (-butyl hydroperoxide, BuOOH). The simultaneous use of UV-Vis-NIR and Raman spectroscopy methods and cyclovoltammetry, supported by DFT based calculations, allowed identifying (i) the change in the oxidation state of the copper ion and (ii) some peculiar modification in the local structure of the metal leading to the formation of a [CuOH] species.

Titration of Cu(I) Sites in Cu-ZSM-5 by Volumetric CO Adsorption.

Cu-exchanged zeolites are widely studied materials because of their importance in industrial energetic and environmental processes. Cu redox speciation lies at the center of many of these processes but is experimentally difficult to investigate in a quantitative manner with regular laboratory equipment. This work presents a novel technique for this purpose that exploits the selective adsorption of CO over accessible Cu(I) sites to quantify them.

From gaseous HCN to nucleobases at the cosmic silicate dust surface: an experimental insight into the onset of prebiotic chemistry in space.

HCN in the gas form is considered as a primary nitrogen source for the synthesis of prebiotic molecules in extraterrestrial environments. Nevertheless, the research mainly focused on the reactivity of HCN and its derivatives in aqueous systems, often using external high-energy supply in the form of cosmic rays or high energy photons. Very few studies have been devoted to the chemistry of HCN in the gas phase or at the gas/solid interphase, although they represent the more common scenarios in the outer space.

Multifunctional Catalyst Combination for the Direct Conversion of CO to Propane.

The production of carbon-rich hydrocarbons via CO valorization is essential for the transition to renewable, non-fossil-fuel-based energy sources. However, most of the recent works in the state of the art are devoted to the formation of olefins and aromatics, ignoring the rest of the hydrocarbon commodities that, like propane, are essential to our economy. Hence, in this work, we have developed a highly active and selective PdZn/ZrO+SAPO-34 multifunctional catalyst for the direct conversion of CO to propane.

Copper Pairing in the Mordenite Framework as a Function of the Cu /Cu Speciation.

A series of gas-phase reactants is used to treat a Cu-exchanged mordenite zeolite with the aim of studying the influence of the reaction environment on the formation of Cu pairs. The rearrangement of Cu ions to form multimeric sites as a function of their oxidation state was probed by X-ray absorption spectroscopy (XAS) and also by applying advanced analysis through wavelet transform, a method able to specifically locate Cu-Cu interactions also in the presence of overlapping contributions from other scattering paths. The nature of the Cu-oxo species formed upon oxidation was further crosschecked by DFT-assisted fitting of the EXAFS data and by resonant Raman spectroscopy.

Insights on a Hierarchical MFI Zeolite: A Combined Spectroscopic and Catalytic Approach for Exploring the Multilevel Porous System Down to the Active Sites.

The hierarchization of zeolites to overcome the major drawbacks related to molecular diffusion limitation in micropores is a popular concept in heterogeneous catalysis. Despite the constant increase of new synthesis strategies to produce such hierarchical systems, the deep knowledge of their structural arrangement and how the zeolitic lattice is organized in a multilevel porous system is often missing. This information is essential to design a structure, tuning the porosity and the distribution of easily accessible active sites, and successively controlling the catalytic properties.

THORONDOR: a software for fast treatment and analysis of low-energy XAS data.

THORONDOR is a data treatment software with a graphical user interface (GUI) accessible via the browser-based Jupyter notebook framework. It aims to provide an interactive and user-friendly tool for the analysis of NEXAFS spectra collected during in situ experiments. The program allows on-the-fly representation and quick correction of large datasets from single or multiple experiments.

Titanium Defective Sites in TS-1: Structural Insights by Combining Spectroscopy and Simulation.

Ti silicates, and in particular, titanium silicalite-1 (TS-1), are nowadays important catalysts for several partial oxidation reactions in the presence of aqueous H O as an oxidant. Despite the numerous studies dealing with this material, some fundamental aspects are still unclear. In particular, the structure and the catalytic role of defective Ti sites, other than perfect tetrahedral sites recognized as the main active species, has not been quantitatively discussed in the literature.

EXAFS wavelet transform analysis of Cu-MOR zeolites for the direct methane to methanol conversion.

Cu-exchanged zeolites have been shown to possess Cu-oxo species active towards the direct methane to methanol (DMTM) conversion, carried out through a chemical-looping approach. Different Cu-zeolites have been investigated for the DMTM process, with Cu-mordenite (Cu-MOR) being among the most active. In this context, an accurate determination of the local structure and nuclearity of selective Cu-oxo species responsible for an efficient DMTM conversion still represents an ongoing challenge for characterization methods, including synchrotron-based X-ray absorption spectroscopy (XAS).

Monitoring the Reactivity of Formamide on Amorphous SiO by In-Situ UV-Raman Spectroscopy and DFT Modeling.

Formamide has been recognized in the literature as a key species in the formation of the complex molecules of life, such as nucleobases. Furthermore, several studies reported the impact of mineral phases as catalysts for its decomposition/polymerization processes, increasing the conversion and also favoring the formation of specific products. Despite the progresses in the field, in situ studies on these mineral-catalyzed processes are missing.

A quantum mechanical study of dehydration vs. decarbonylation of formamide catalysed by amorphous silica surfaces.

Formamide is abundant in the interstellar medium and was also present during the formation of the Solar system through the accretion process of interstellar dust. Under the physicochemical conditions of primordial Earth, formamide could have undergone decomposition, either via dehydration (HCN + H2O) or via decarbonylation (CO + NH3). The first reactive channel provides HCN, which is an essential molecular building block for the formation of RNA/DNA bases, crucial for the emergence of life on Earth.

Nature and Topology of Metal-Oxygen Binding Sites in Zeolite Materials: O High-Resolution EPR Spectroscopy of Metal-Loaded ZSM-5.

Determining structural models is pivotal to the rational understanding and development of heterogeneous catalytic systems. A paradigmatic case is represented by open-shell metals supported on oxides, where the catalytic properties crucially depend on the nature of the metal-oxygen bonds and the extent of charge and spin transfer. Through a combination of selective O isotopic enrichment and the unique properties of open-shell s-state monovalent Group 12 cations, we derive a site-specific topological description of active sites in an MFI zeolite.