Deactivation of metal-based catalysts for vinyl chloride synthesis via acetylene hydrochlorination is often dictated by indispensable, catalytically-active carbon supports, but underlying mechanisms remain unclear. Carbon nitrides offer an attractive platform for studying them thanks to ordered structure and high N-content, which facilitates coking. Herein, we monitor the life and death of carbon nitride supports for Pt single atoms in acetylene hydrochlorination, demonstrating that specific N-functionalities and their restructuring cause distinct deactivation mechanisms. Varying polymerization and exfoliation degrees in pristine carbon nitrides (i.e., -NHx termination and N-vacancy concentrations), we establish graphitic and pyridinic N-atoms as C2H2 adsorption sites and pyridinic N-vacancies as coking sites through kinetic and spectroscopic analyses. Uniquely suited for probing point defects, operando electron paramagnetic spectroscopy, coupled to simulations, reveals that HCl drives depolymerization, by protonating heptazine-linking graphitic N-atoms, and generates graphitic N-vacancies, forming NH3. These reduce C2H2 adsorption and promote radical polymerization into coke, respectively, without altering Pt atoms. Design guidelines to mitigate deactivation are discussed, highlighting the importance of tracking active functionalities in carbons.

C1 coupling reactions over zeolite catalysts are central to sustainable chemical production strategies. However, questions persist regarding the involvement of CO in ketene formation, and the impact of this elusive oxygenate intermediate on reactivity patterns. Using operando photoelectron photoion coincidence spectroscopy (PEPICO), we investigate the role of CO in methyl chloride conversion to hydrocarbons (MCTH), a prospective process for methane valorization with a reaction network akin to methanol to hydrocarbons (MTH) but without oxygenate intermediates. Our findings reveal the transformative role of CO in MCTH at the low pressures, inducing ketene formation in MCTH and boosting olefin production, confirming the Koch carbonylation step in the initial stages of C1 coupling. We uncover pressure-dependent product distributions driven by CO-induced ketene formation, and its subsequent desorption from the zeolite surface, which is enhanced at low pressure. Inspired by the above results, extension of the co-feeding approach to CH3OH as another simple oxygenate showcases the additional potential for improved catalyst stability in MCTH at ambient pressure.

Layered black phosphorus (BP) is endowed with peculiar chemico-physical properties that make it a highly promising candidate in the field of electronics. Nevertheless, as other 2D materials with atomic scale thickness, it suffers from easy degradation under ambient conditions. Herein, it is shown that the functionalization of BP with preformed and in situ grown Ni NPs, affects the electronic properties of the material. In particular, Ni functionalization performed in situ leads to a narrowing of the average BP band gap from 1.15 to 0.95 eV and to a marked shift in the conduction band maximum from -0.33 V to -0.07 V, which, in turn, improve the ambient stability. Structural studies carried out by XAS can well distinguish the two nanohybrids and reveal that once Ni NPs are grown on BP nanosheets, a Ni-P coordinative bond is formed, featuring a short Ni-P distance of 2.27 Å, which is not observed when preformed Ni NPs are immobilized on BP. Comparing the XANES and EXAFS spectra of fresh and aged samples of both nanohybrids, suggests that the interaction between Ni and P atoms results in a stabilization effect exerted via a dual electronic and redox mechanism, that infers a much superior ambient stability to BP, even if the surface functionalization is far to achieve a full coverage.

Practical implementation of CH2Br2 hydrodebromi-nation to CH3Br, an important step in the bromine-mediated functionalization of methane, is currently hindered by the lack of selective and stable catalysts, which typically deactivate over a few hours on stream. Despite ranking as the most active metal for this reaction, palladium has received limited attention due to the tendency of metal nanoparticles to form C2+ products and methane, alongside CH3Br. Herein, we explore metal nuclearity and host effects in nanostructured palladium-based hydrodebromi-nation catalysts. While Pd nanoparticles intrinsically exhibit similar unselective behavior irrespective of the host choice, encompassing metal oxides and carbon-based supports, stabilization of isolated Pd sites over the latter enables suppression of C-C coupling. Therein, the impact of host functionalization and structure on the metal center reactivity is investigated over amorphous activated and nitrogen-doped carbons as well as crystalline carbon nitrides. By maximizing the site architectural uniformity and integrating large N-cavities with high affinity for the metal, we show that high-valent Pd single atoms supported on a poly(triazine imide) carbon nitride unlocks full selectivity to CH3Br (99%) and stable behavior over 24 h on stream. Finally, by combining spectroscopic, kinetic, and computational analyses, we identify that the oxidation state of the metal centers, regulated by the coordination with the host, dictates their thermodynamic propensity to selectively hydrogenate the CH2Br* intermediate to CH3Br.

Binary ruthenium-phosphorus nanoparticles (NPs) with different Ru/P ratio were prepared in mild conditions using white phosphorus (P-4) as phosphorus source. Accurate study of both their morphology and structure at the atomic level by TEM and HAADF-STEM, respectively, showed that Ru2P and RuP have a narrow size distribution (ca. 3.3 nm) and are lacking an ordered ruthenium phosphide lattice. P-31 Solid State NMR highlighted the existence of three different phosphorus species consistently with the lack of a metal phosphide lattice and finally XPS revealed that the true nature of these nanoparticles can be better described as a ruthenium-phosphorus alloy. As a benchmark test, the selective hydrogenation of nitroarenes to primary aromatic amines was studied and evidenced how the P-alloying imparts a surface modification resulting in a higher catalytic activity and excellent chemoselectivity of Ru2P in comparison to Ru(0) and RuP.

This review comprehensively covers the coordination chemistry of elemental phosphorus during the years 2011-2020. The main part is dedicated to the activation of white phosphorus mediated by early and late transition metals and its subsequent reactivity once in the coordination sphere of a metal. The burgeoning interest towards early TMs has opened the way to new coordination topologies and types of reactivity. Meanwhile, the coordination chemistry of P4 towards late transition metal elements has also attracted significant attention. Numerous studies have targeted transformations of P4-derived phosphorus ligands and the subsequent release of said ligand fragments. The final part of this review focuses on the black allotrope of phosphorus, which offers a polydentate phosphorus surface able to interact with transition metals forming new functionalized 2D materials. (C) 2021 The Authors. Published by Elsevier B.V.

In the rapidly emerging field of layered two-dimensional functional materials, black phosphorus, the P-counterpart of graphene, is a potential candidate for various applications, e.g., nanoscale optoelectronics, rechargeable ion batteries, electrocatalysts, thermoelectrics, solar cells, and sensors. Black phosphorus has shown superior chemical sensing performance; in particular, it is selective for the detection of NO2, an environmental toxic gas, for which black phosphorus has highlighted high sensitivity at a ppb level. In this work, by applying a multiscale characterization approach, we demonstrated a stability and functionality improvement of nickel-decorated black phosphorus films for gas sensing prepared by a simple, reproducible, and affordable deposition technique. Furthermore, we studied the electrical behavior of these films once implemented as functional layers in gas sensors by exposing them to different gaseous compounds and under different relative humidity conditions. Finally, the influence on sensing performance of nickel nanoparticle dimensions and concentration correlated to the decoration technique and film thickness was investigated.

The chemical functionalization of 2D exfoliated black phosphorus (2D BP) continues to attract great interest, although a satisfactory structural characterization of the functionalized material has seldom been achieved. Herein, we provide the first complete structural characterization of 2D BP functionalized with rare discrete Pd2 units, obtained through a mild decomposition of the organometallic dimeric precursor [Pd(η3-C3H5)Cl]2. A multitechnique approach, including HAADF-STEM, solid-state NMR, XPS, and XAS, was used to study in detail the morphology of the palladated nanosheets (Pd2/BP) and to unravel the coordination of Pd2 units to phosphorus atoms of 2D BP. In particular, XAS, backed up by DFT modeling, revealed the existence of unprecedented interlayer Pd-Pd units, sandwiched between stacked BP layers. The preliminary application of Pd2/BP as a catalyst for the hydrogen evolution reaction (HER) in acidic medium highlighted an activity increase due to the presence of Pd2 units.

Among the novel class of mono-elemental two-dimensional (2D) materials, termed Xenes, phosphorene is emerging as a great promise for its peculiar chemical and physical properties. This review collects a selection of the recent breakthroughs that are related to the application of phosphorene in catalysis and electrocatalysis. Noteworthy, thanks to its intrinsic Lewis basic character, pristine phosphorene turned out to be more efficient and more selective than other non-metal catalysts, in chemical processes as the electroreduction of nitrogen to ammonia or the alkylation of nucleophiles with esters. Once functionalized with transition metals nanoparticles (Co, Ni, Pd, Pt, Ag, Au), its catalytic activity has been evaluated in several processes, mainly hydrogen and oxygen evolution reactions. Under visible light irradiation, it has shown a great improvement of the activity, demonstrating high potential as a photocatalyst.

This work aims at characterizing for the first time the 31P spin interactions determining the nuclear magnetic resonance (NMR) properties of solid black phosphorus (bP) and of its few-layer exfoliated form (fl-bP). Indeed, the knowledge of these properties is still very poor, despite the great interest received by this layered phosphorus allotrope and its exfoliated 2D form, phosphorene. By combining density functional theory (DFT) calculations and solid-state NMR experiments on suspensions of fl-bP nanoflakes and on solid bP, it has been possible to characterize the 31P homonuclear dipolar and chemical shift interactions, identifying the network of 31P nuclei more strongly dipolarly coupled and highlighting two kinds of magnetically nonequivalent 31P nuclei. These results add an important missing piece of information to the fundamental chemico-physical knowledge of bP and support future extensive applications of NMR spectroscopy to the characterization of phosphorene-based materials.

The burgeoning interest in two-dimensional (2D) black phosphorus (bP) contributes to the expansion of its applications in numerous fields. In the present study, 2D bP is used as a support for homogeneously dispersed palladium nanoparticles directly grown on it by a wet chemical process. Electron energy loss spectroscopy–scanning transmission electron microscopy analysis evidences a strong interaction between palladium and P atoms of the bP nanosheets. A quantitative evaluation of this interaction comes from the X-ray absorption spectroscopy measurements that show a very short Pd–P distance of 2.26 Å, proving for the first time the existence of an unprecedented Pd–P coordination bond of a covalent nature. Additionally, the average Pd–P coordination number of about 1.7 reveals that bP acts as a polydentate phosphine ligand toward the surface of the Pd atoms of the nanoparticles, thus preventing their agglomeration and inferring with structural stability. These unique properties result in a superior performance in the catalytic hydrogenation of chloronitroarenes to chloroanilines, where a higher chemoselectivity in comparison to other heterogeneous catalyst based on palladium has been observed.

Phosphorene, the 2D material derived from black phosphorus, has recently attracted a lot of interest for its properties, suitable for applications in materials science. The physical features and the prominent chemical reactivity on its surface render this nanolayered substrate particularly promising for electrical and optoelectronic applications. In addition, being a new potential ligand for metals, it opens the way for a new role of the inorganic chemistry in the 2D world, with special reference to the field of catalysis. The aim of this review is to summarize the state of the art in this subject and to present our most recent results in the preparation, functionalization, and use of phosphorene and its decorated derivatives. We discuss several key points, which are currently under investigation: the synthesis, the characterization by theoretical calculations, the high pressure behavior of black phosphorus, as well as its decoration with nanoparticles and encapsulation in polymers. Finally, device fabrication and electrical transport measurements are overviewed on the basis of recent literature and the new results collected in our laboratories.