Reactive Center Research Articles

Coordinatively unsaturated atomically dispersed Pt+2-N4 sites on hexagonal nanosheet structure of g-C3N4 for high-performance photocatalytic H2 production

Developing active and stable metal single-atom catalysts is technically challenging. The electronic interactions between the metal site and its supports play a key role in altering electronic properties for the creation of more reactive and stable centers. The local environment of a single-atom catalyst directly affects its stability and reactivity. Herein, we describe the formation of coordinatively unsaturated atomically dispersed Pt+2 sites (Pt+2-N4) on hexagonal nanosheets of g-C3N4 (Pt1-HCN). This structure with Pt loading of 0.38 wt% exhibited a superb photocatalytic hydrogen evolution rate of 2900 µmol g−1 h−1 which was 5.6 times higher than that of the reactive Pt1 sites (Pt+4-N5) on bulk (Pt1-BCN). The comprehensive advance spectroscopic analysis combined with DFT calculations revealed that the strong electronic metal-support interactions between Pt1 and HCN effectively reduced the adsorbed Pt+4 sites into Pt+2 and create favorable uniform Pt+2-N4 moieties at low Pt loading for water adsorption, dissociation, and H2 evolution.

Constructing of Mn4+-O-PdOx sites in SmMn2O5 Mullite: Novel and Highly-Active reactive centers for Low-Temperature methane combustion

Pd-based catalysts have been widely investigated for CH4 combustion yet they still suffer from inefficiency at low temperatures. Herein, a novel strategy was implemented to create a new type of highly active and stable Mn4+-O-PdOx center by doping Pd into SmMn2O5 lattice and modifying it with acid etching. Compared with the impregnation-method, T50 of the catalyst (SMPO-OA) synthesized by this strategy was reduced by 210 °C, and TOF value increased more than 6 times at 260 °C. Importantly, it showed the superior thermal stability and water resistance. Various characterization results indicate that Pd successfully occupied the Mn3+ position in the pyramid unit and formed abundant Mn-O-Pd linkage. Acid treatment introduced the unsaturated-coordination Mn4+-O-PdOx center, which showed high-activity for the methane activation. In-situ DRIFTS and Quasi-in-situ XPS indicate that methane oxidation on the SMPO-OA surface followed MvK mechanism, and activation ability of CH bond at low temperature was markedly improved.

Directional Separation of Highly Reductive Electrons to the Reactive Center in a Magnetic S-Scheme ZnFe2O4/A-MoS2 Heterojunction for Enhanced Peroxymonosulfate Activation toward Pharmaceuticals and Personal Care Product Removal.

Pharmaceuticals and personal care products (PPCPs) are ubiquitous in sewage, adversely affecting ecosystems and human health. In this study, an S-scheme magnetic ZnFe2O4/ammoniated MoS2 (ZnFe2O4/A-MoS2) heterojunction as a visible-light-driven PMS activator for PPCP degradation was developed. ZnFe2O4/A-MoS2 achieves improved photocatalytic activity because the construction of S-scheme heterojunction promotes the separation of the highly reductive photogenerated electrons. The optimized photocatalyst (10%-ZnFe2O4/A-MoS2, 0.2 g/L) achieved 100% removal of 2 ppm carbamazepine (CBZ) within 2.5 min at a PMS dosage of 0.5 mM (initial pH 7.0). Mechanistic investigation revealed that the separated electrons to the ZnFe2O4 reactive center of the heterojunction facilitated PMS activation and generated SO4·- as the dominant reactive species for CBZ degradation. The system exhibited excellent practicability in various samples of actual sewage, where most sewage components negatively impacted CBZ degradation. Further, the chloride ions in high-salinity sewage could be activated to generate additional reactive chlorine species for PPCP degradation. The heterojunction possesses outstanding reusability and stability in treating various water conditions. This work provides mechanistic and practical perspectives in developing novel S-type heterojunctions for recalcitrant pollutant treatment.

Elucidating the charge redistribution in bimetallic metal–organic frameworks: High-electron-density reactive center for removal of organic micropollutants in water

For the elimination of pharmaceutical and personal care products (PPCPs) from water, various methods and materials have been designed, while the removal effect of PPCPs is still mediocre due to the limitation of trace concentration. Therefore, constructing high-electron-density reactive centers (HRCs) for effective processing is urgent due to the potential threat to human health posed by PPCPs in water. Herein, a bimetallic metal–organic framework (BMOF-Ti/Zr6%) was synthesized by a solvothermal method with enhanced adsorption and photocatalytic capacity to address the issue. The Zr doping in metal clusters elevated the adsorption capacity of 2,2′,4,4′-tetrehydroxybenzophenone (BP-2) on BMOF-Ti/Zr6% to 4032 μmol/g, and the photocatalytic rate was more than 6 times higher than that of the pristine metal–organic framework. The enhanced adsorption and photodegradation of PPCPs on BMOFs was ascribed to the charge redistribution between Ti and Zr inducing the formation of HRCs. The electrons accumulated on HRCs altered the adsorption performance of metal sites and facilitated the generation of reactive oxygen species, which was further confirmed by theoretical calculations and indirectly validated by the interface behaviors of dissolved organic matter (DOM). Moreover, the possible reaction pathway of BP-2 degradation was explored. In addition, the BMOF-Ti/Zr6% retained more than 90% of initial adsorption capacity in photocatalytic regeneration experiments, demonstrating the potential for application in natural water matrix. These findings reinforce the understanding of charge behaviors in bimetallic materials and contribute to understand the impact of DOM in water remediation processes.

Furfural adsorption on the g-C3N4 monolayer: A DFT analysis

Graphitic carbon nitride (g-C3N4) has attracted much attention in recent years as a material for catalytic processes due to its promising structural and physicochemical properties. However, the role played by the g-C3N4 during the catalytic activity is often briefly discussed. Consequently, the mechanism behind these substrate-adsorbate processes involving g-C3N4 still needs to be better understood. This study analyzed furfural (FAL) adsorption on h-g-C3N4 monolayers based on DFT, including Van der Waals (vdW) interactions. To elucidate the role of the h-g-C3N4 in catalytic systems, the adsorption of a FAL molecule was evaluated at high and low coverages. At high coverage, due to proximity effects, FAL molecules interact with neighboring FAL molecules forming a monolayer that lays over the h-g-C3N4 nanosheet. At low coverage, weak interactions govern the FAL-h-g-C3N4 interaction. In both cases, vdW interactions are the main forces that bring stability to the composites. No chemical interactions are observed. The obtained results led us to conclude that in reactions including FAL and h-g-C3N4 nanosheets, the latter will serve as a support structure that favors the adsorbate mobility to reach the reactive centers.

Identifying Fe as OER Active Sites and Ultralow-Cost Bifunctional Electrocatalysts for Overall Water Splitting.

Electrocatalysts based on Fe and other transition metals are regarded as most promising candidates for accelerating the oxygen evolution reaction (OER), whereas whether Fe is the catalytic active site for OER is still under debate. Here, unary Fe- and binary FeNi- based catalysts, FeOOH and FeNi(OH)x , are produced by self-reconstruction. The former is a dual-phased FeOOH, possessing abundant oxygen vacancies (VO ) and mixed-valence states, delivering the highest OER performance among all the unary iron oxides- and hydroxides- based powder catalysts reported to date, supporting Fe can be catalytically active for OER. As to binary catalyst, FeNi(OH)x is fabricated featuring 1) an equal molar content of Fe and Ni and 2) rich VO , both of which are found essential to enable abundant stabilized reactive centers (FeOOHNi) for high OER performance. Fe is found to be oxidized to 3.5+ during the *OOH process, thus, Fe is identified to be the active site in this new layered double hydroxide (LDH) structure with Fe:Ni = 1:1. Furthermore, the maximized catalytic centers enable FeNi(OH)x @NF (nickel foam) as low-cost bifunctional electrodes for overall water-splitting, delivering excellent performance comparable to commercial electrodes based on precious metals, which overcomes a major obstacle to the commercialization of bifunctional electrodes: prohibitive cost.

Porous Salts as Platforms for Heterogeneous Catalysis.

The preparation of a new class of reactive porous solids, prepared via straightforward salt metathesis reactions, is described here. Reaction of the dimethylammonium salt of a magnesium-based porous coordination cage with the chloride salt of [CrII Cl(Me4 cyclam)]+ affords a porous solid with concomitant removal of dimethylammonium chloride. The salt consists of the ions combined in the expected ratio based on their charge as confirmed by UV-vis and X-ray photoelectron spectroscopies, ion chromatography (IC), and inductively coupled plasma mass spectrometry (ICP-MS). The porous salt boasts a Brunauer-Emmett-Teller (BET) surface area of 213m2 g-1 . Single crystal X-ray diffraction reveals the chromium(II) cations in the structure reside in the interstitial space between porous cages. Importantly, the chromium(II) centers, previously shown to react with O2 to afford reactive chromium(III)-superoxide adducts, are still accessible in the solid state as confirmed by UV-vis spectroscopy. The site-isolated reactive centers have competence toward hydrogen atom abstraction chemistry and display significantly increased stability and reactivity as compared to dissolved ions.

Pathomorphological changes in the organs of the peripheral immune system in mycobacteriosis of cattle

Conducting routine allergy tests of cattle with a simultaneous sample in TB-prone farms is necessary to confirm the stage of the epizootic process. The purpose of the research – to explore the pathomorphological changes in cows upon detection of para allergic reactions during diagnostic testing for tuberculosis. The diagnosis of tuberculosis in animals was performed comprehensively using all methods for tuberculosis control provided for in the guidelines – epidemiological, clinical, allergic, pathological, histomorphological, bacteriological and biological. It allowed establishing that the reactions to tuberculin in cows were of a paraallergic nature, caused by nontuberculous mycobacteria or so-called atypical mycobacteria. It was determined that cows that reacted positively to tuberculin and an atypical mycobacterial allergen and were sent for slaughter for diagnostic purposes did not demonstrate pathological changes characteristic of tuberculosis. However, pathological changes (granulomatous foci, atrophy of lymphoid and epithelioid tissue, hyperplasia of varying intensity and nature, dotted haemorrhages in the cortical zone) were observed in many lymph nodes, including mediastinal, mesenteric, pharyngeal and mandibular lymph nodes, indicating an active infectious process in the body of animals caused by nontuberculous mycobacteria. Therewith, several changes were observed in the lymph nodes during histomorphological examination: development of primary nodules of lymphocytes and reticular tissue in reactive centres, degradation and necrosis of lymphocytes, the establishment of cellular detritus in the centre of the nodules and capsules of epithelioid elements around the nodules, etc., which can be used to confirm the patterns of pathology development and, indirectly, the mechanism of sensitisation of the cow’s body, and therefore the nature of paraallergic reactions in animals. The obtained results are important for the timely detection and identification at the histomorphological level of a complex of changes in the organs and tissues of cows due to the penetration of nontuberculous mycobacteria, which is the key to the successful diagnosis of primary foci of mycobacteriosis and their effective prevention

Insights into atomically dispersed reactive centers on g-C3N4 photocatalysts for water splitting

Co-catalysts decorations provide unique opportunities in promoting the photocatalytic water splitting performance of graphite carbon nitride (g-C 3 N 4 ) system, while mechanistic understanding of this complex catalytic network remains elusive. Here, taking the single-atom-based photocatalysts (M 1 -g-C 3 N 4 ) as an unprecedented simplified model system, we theoretically tracked the photocatalytic kinetics for a comprehensive understanding of the photocatalytic process and affords the descriptor α S1-T1/ α T1-S0 (ratio of the extent of S 1 -T 1 and T 1 -S 0 state mixing) and Δ G H* (hydrogen adsorption free energy) for rational screening of photocatalysts. The targeted Fe 1 -g-C 3 N 4 yielded an excellent H 2 evolution rate (ca. 3.2 mmol g cat −1 h −1 under full arc), two order of magnitude improvement relative to pristine g-C 3 N 4 counterpart and also outperforms other representative 3 d -transition-metal-based photocatalysts. This work presents a comprehensive understanding of the essential role of isolated atomic sites in the photocatalytic course and sheds light on the design of photocatalysts from both photophysical/photochemical aspects. This work presents a comprehensive understanding of the essential role of isolated atomic sites in the photocatalytic process based on a combination of theoretical with experimental studies. The photophysical, photochemical descriptors of α S1-T1/ α T1-S0 (ratio of the extent of S 1 -T 1 and T 1 -S 0 state mixing) and Δ G H* (hydrogen adsorption free energy) are proposed for rational screening of photocatalysts. • The photocatalytic courses of a prototype single-atom-based photocatalysts (M 1 -g-C 3 N 4 ) were tracked based on a combination of DFT calculations with experimental studies. • General descriptors α S1-T1/ α T1-S0 (ratio of the extent of S 1 -T 1 and T 1 -S 0 state mixing) and Δ G H* (hydrogen adsorption free energy) were proposed for rational screening of photocatalysts. • The targeted Fe 1 -g-C 3 N 4 yielded excellent H 2 evolution rate (ca. 3.2 mmol g cat −1 h −1 under full arc), two order of magnitude improvement relative to pristine g-C 3 N 4 and also outperforms other representative 3 d -transition-metal-based photocatalysts.

Bimetal-organic layer-derived ultrathin lateral heterojunction with continuous semi-coherent interfaces for boosting photocatalytic CO2 reduction

Current heterojunction photocatalysts suffer from sluggish charge transfer due to the discontinuous interfaces at an atomic level. Herein, we report a NiO–Co3O4 ultrathin lateral heterojunction using NiCo-based bimetal–organic layers as precursors. The atomic-resolution images display a unique continuous semi-coherent interface between NiO and Co3O4. The experimental results confirm that the continuous semi-coherent interfaces effectively expedite the electron transfer from NiO to Co3O4. Concomitantly, the electron transfer raises d-band center of Co3O4 in NiO–Co3O4 toward Fermi level, as revealed by the density functional theory calculations. As a result, the *COOH intermediate can be strongly bound on cobalt reactive centers. The successful modulation of charge transfer and intermediate binding by continuous semi-coherent interfaces leads to a remarkable gas yield of 22.67 mmol h−1 from photocatalytic CO2 reduction over NiO–Co3O4. This work highlights the crucial roles of interface engineering in regulating carrier kinetics and surface reactions.

Self-Assembled p–n Homojunction in SnS2 Nanosheets for Enhanced Visible Light-Driven Photocatalysis

Defect engineering and hetero-interfacial bending are standard approaches for enhancing carrier separation and increasing visible light absorption in a semiconductor photocatalyst. Here, we demonstrate the evolution of sulfur vacancies (VS) and the self-assembly of a p–n homojunction through prolonged aqueous washing of SnS2 nanosheets. The experimental studies have validated increased hydrophilicity, layer thinning, VS generation, and extended photocarrier lifetime in washed SnS2 nanosheets. Density functional theory has revealed the changes in the local electronic structure of SnS2 in the presence of structural defects. An electrochemical impedance spectroscopy study has shown that VS actuates the self-assembly of a pseudo-p-type SnS layer over n-type SnS2 to generate the p–n homojunction. The p-type carrier densities are increased twice as the number of washings is increased from 3 to 10 times. The photocatalytic efficacy of the SnS2 homojunction is evaluated in the study of the degradation of several water contaminants under white light and monochromatic excitations. The proposed mechanism shows that the built-in electric field at the p–n junction promotes the separation of the photogenerated electrons and holes. Meanwhile, VS traps the electrons and transfers them to the catalytically reactive centers to participate in photocatalysis. Our findings demonstrate that a simple approach that involves prolonged aqueous washing of as-produced SnS2 promotes the formation of VS and the self-assembly of a p–n homojunction in SnS2 nanosheets with improved visible light photocatalytic performances.

Heme Scavenging and Delivery: The Role of Human Serum Albumin

Heme is the reactive center of several metal-based proteins that are involved in multiple biological processes. However, free heme, defined as the labile heme pool, has toxic properties that are derived from its hydrophobic nature and the Fe-atom. Therefore, the heme concentration must be tightly controlled to maintain cellular homeostasis and to avoid pathological conditions. Therefore, different systems have been developed to scavenge either Hb (i.e., haptoglobin (Hp)) or the free heme (i.e., high-density lipoproteins (HDL), low-density lipoproteins (LDL), hemopexin (Hx), and human serum albumin (HSA)). In the first seconds after heme appearance in the plasma, more than 80% of the heme binds to HDL and LDL, and only the remaining 20% binds to Hx and HSA. Then, HSA slowly removes most of the heme from HDL and LDL, and finally, heme transits to Hx, which releases it into hepatic parenchymal cells. The Hx:heme or HSA:heme complexes are internalized via endocytosis mediated by the CD91 and CD71 receptors, respectively. As heme constitutes a major iron source for pathogens, bacteria have evolved hemophores that can extract and uptake heme from host proteins, including HSA:heme. Here, the molecular mechanisms underlying heme scavenging and delivery from HSA are reviewed. Moreover, the relevance of HSA in disease states associated with increased heme plasma concentrations are discussed.

Robust TiO2/CuS@TiO2 composites loaded on Ti mesh with outstanding stability and photothermal effects for the enhanced photo-degradation of organic pollutions in a flowing device

A scalable strategy with commercial feasibility was developed to in situ generate TiO2 nanowires/amorphous CuS@TiO2 nanolayer (TiO2/CuS@TiO2) composites on the surface of titanium mesh through a sequent hydrothermal method, successive ionic layer adsorption and reaction (SILAR), and atomic layer deposition (ALD) techniques. The TiO2/CuS@TiO2 composites could respectively harness the incident light with different spectra at the photothermal center (CuS, visible and near-infrared light) and photocatalytic center (TiO2, UV and visible light), which leads to the effective utilization of the solar energy. Benefiting from the CuS photothermal-induced local heating effect of CuS, the adjacent micro-zone temperature could be elevated and the activation energy barrier could be reduced by 10.5 kJ mol−1, which promotes the activation of surface lattice oxygen and dissolved oxygen in the photocatalytic process. Meanwhile, the ALD generated TiO2 nanolayer could both serve as reactive centers but also protecting armor for the CuS, which prohibited the peeling and oxidation of the thermal centers, leading to a high stability of the photocatalyst, which exhibits no obvious fading after 20-cycle reuse. A flow reactor was conceived and made by 3D print and the Ti-mesh based photocatalyst was integrated, which demonstrates high photocatlytic performances, manifesting its great potential for large-scale water treatment.

Polypropylene film surface modification for improving its hydrophilicity for innovative applications

Organic polymeric materials, especially polyolefins, contain mainly C and H atoms and thus present serious surface problems due to low surface energy and reactive inertness. Using method developed in this work it is possible to convert the H atoms of the polypropylene (PP) film surface into polar groups by treatment with a mixture of chromic, sulphuric, and phosphoric acids in a short time at elevated temperature. Hydroxyl and carboxyl groups on the surface of materials not only determine their chemical and physical properties, but also provide reactive centers for various applications. Optical microscopy (OM) and atomic force microscopy (AFM) analyses have shown that induced surface modification of the PP film causes mainly physical changes, creating microcraters and surface roughness and hence increasing surface tension, while X-ray diffraction (XRD) analysis has confirmed the absence of phase changes. The attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy analysis has confirmed the grafting of polar groups, such as hydroxyl, carboxyl, and carbonyl onto the surface of the PP. This indicates that used mixture destroyed or at least broke down to some extent the covalent bonds of the main carbon skeletons, which were present on PP substrate surfaces and improved surface wettability and zeta potential. The simultaneous thermal analysis (thermogravimetry (TG) and differential scanning calorimetry (DSC)) results have shown that the presence of polar groups in the PP-[O] film samples affects the melting and decomposition temperatures; they are higher than those of PP film. The change in the enthalpy of melting indicated a change in the surface energy. The band gap (Eg) determined from diffuse reflectance spectra in the UV-visible region by the Kubelka-Munk method has decreased for modified PP films, and they have become more suitable for optoelectronics.

Methods of synthesis of 1,2,4-triazole derivatives with methoxyphenyl and study the spectrum of their pharmacological activity

In today’s society, the work of a pharmaceutical worker is very respectful, because it is difficult to imagine the treatment of people without the use of drugs. As time passes, the number of diseases with their own characteristics only increases, so the creation of drugs of synthetic origin remains an actual task for scientists around the world. There are a large number of heterocyclic systems, the derivatives of which exhibit a wide range of pharmacological activities, namely, furan, pyrrole, pyrazole, pyridine, pyrimidine, purine, and many others. Particular attention is drawn to structures that have low toxicity. Undoubtedly, the initial heterocyclic substance must have several reactive centers in order to build the most effective pharmacophores. Studies by scientists from around the world point to the prospect of using derivatives of the 1,2,4-triazole heterocyclic system as models for new biologically active substances. The aim of the work was to summarize data on modern methods for the synthesis of 1,2,4-triazole derivatives, to determine the effect of a methoxyphenyl substituent on reactivity and changing the spectrum of pharmacological activity. Materials and methods. In the work, we used such methods as analytical, information search, descriptive, generalization. The materials of the research were information from the professional literature on the methods of synthesis and study of the biological activity of 1,2,4-triazole derivatives with methoxyphenyl. Results. A search, analysis, and generalization of information on the methods of synthesis and study of the biological activity of 1,2,4-triazole derivatives with methoxyphenyl were carried out. As a result of the studying available sources and implementation of scientific research, it was found that studies of 1,2,4-triazole derivatives with methoxyphenyl occupy an important place in the Ukrainian pharmaceutical industry, as they have a wide range of pharmacological activity. Also they show low rates of acute toxicity and are perspective to create new APIs on their base Conclusions. Processing, analysis, systematization, comparison, and generalization of modern sources of information indicate a wide synthetic variability, a fairly wide range of biological activity, and low rates of acute toxicity of 1,2,4-triazole derivatives, with methoxyphenyl at the 5th position of the nucleus of this heterocycle and a wide range of their applications.

Молекулярное моделирование и экспериментальное подтверждение поиска средств коррекции токсического воздействия сероводорода

Mathematical modeling is a promising method enabling in silico calculations with subsequent suggestion of cell membrane protective agents used to reduce the consequences of exposure to hydrogen sulfide-containing gas in emergency situations. This study aimed to investigate the nature of interaction of hydrogen sulfide (H2S) and N-Acetyl-L-Cycteine (NAC) with the components of cell membranes. We built a mathematical model of interatomic interactions of cell membrane components with H2S and NAC (two separate models), then made the quantum-chemical calculations using our proprietary technique and set up GAMESS Z-matrices reflecting type and position of atoms in the molecules. The structure of the molecules was optimized with the help of MOPAC package built into ChemOffice. Lecithin-based liposomes in a sulfide solution (with Na2S being the donor of H and HS ions) were used as an experimental model of the biological membrane. Redox potential in mV was the comparison parameter in assessment of interaction of the H2S system components and NAC with phospholipid. The results include patterns showing the phospholipid reactive centers blocked by NAC under toxic exposure to H2S. Liposomal models of cell membranes were formed and redox parameters measured. Biological experiment confirmed the acceptable accuracy of the designed method of calculation of intermolecular interactions when used as a basis for further selection of agents capable of adjusting toxic doses of hydrogen sulfide. Membrane models of H2S interaction with protein and lecithin were visualized in silico and in vitro. The possibility of using NAC as an H2S inhibitor has been confirmed.

Construction of F–F@FeVO4/ZnCo2O4 photocatalysts with heterojunction interfacial enhancement and surface oxygen vacancies for the removal of tetracycline, sulfamethoxazole, ciprofloxacin and Cr(VI)

For the purpose of promoting application of green and sustainable photocatalytic materials in real-world composite wastewater remediation, developing stable, efficient and pollution-free treatment devices is necessary and actually urgent. We grew vertical nanosheets consisting of FeVO4/ZnCo2O4 directly on the surface of iron foam (F–F), which intertwined to form F–F@FeVO4/ZnCo2O4 p-n heterojunction catalysts with a three-dimensional framework structure. The F–F@FeVO4/ZnCo2O4 photocatalyst showed excellent photocatalytic performance achieving 96.32%, 92.85%, 95.92% and 97.17% removal efficiencies in the presence of tetracycline (TC), sulfamethoxazole (SMX), ciprofloxacin (CIP) and Cr(VI), respectively. In addition, the photocatalyst was assembled into a simulated photoreactor, enabling the continuous treatment of composite wastewater. The reactor achieved removal efficiencies of 94.81%, 90.02%, 94.17% and 97.15% for TC, SMX, CIP and Cr(VI), respectively, in a 100 min reaction. Furthermore, only after ten photocatalytic cycles under visible light does the catalytic efficiency of the reactor decrease slightly. The excellent performance may be attributed to unique structures that reduce visible light reflection and provide highly reactive reaction centers, as well as surface oxygen vacancies and heterojunctions to accelerate photocarrier separation and free radical generation. The high porosity of F–F also reduces the obstruction of visible light between branches. Moreover, the method of growing FeVO4/ZnCo2O4 active components on F–F overcomes a number of problems (increased interfacial charge transfer impedance, poor structural stability and nonuniform distribution, etc.) associated with conventional methods of combining nanomaterials with recyclable substrates (loading, introduction of adhesives and hybridization, etc.). Density functional theory (DFT) calculations explain the mechanism of interface enhancement.

Selective Photocatalytic Conversion of Methane Induced by Lewis Acid–Base Pair on the Surface of In2O3/TiO2 Heterojunction Photocatalyst

The efficient catalytic conversion of light-driven methane (CH4) is still very challenging. Here, the surface-reconstructed In2O3/TiO2 heterojunction photocatalyst is successfully prepared by a two-step operation of ion exchange and calcination, and the efficient selective photocatalytic conversion of CH4 is achieved. In the absence of O2, the formation rates of ethane (C2H6) and hydrogen (H2) are 68.9 and 78.6 μmol h–1 g–1, respectively, which corresponds to the stoichiometric ratio. However, in the presence of O2 or water (H2O) as the oxidant, CH4 is converted to CO, and the CO formation rates are 113.2 and 94.4 μmol h–1 g–1, respectively. Our results show that the In3–O2– Lewis acid–base pair on the In2O3/TiO2 surface can realize the adsorption and activation of CH4. Moreover, the photogenerated hole-induced reactive oxygen centers (Ti4+O·–Ti4+OH– and Ti4+O2–Ti4+O·–) on the surface of In2O3/TiO2 are identified as the active species for inducing the dissociation of CH4 into ·CH3 radicals, which in turn are coupled into C2H6 by ·CH3. In contrast, in the presence of O2, the surface superoxide anion (O2–), surface ·O– radicals, and O22– anions are identified as the active species for inducing the oxidation of CH4 into CO.

Exploring the Parameters Controlling Product Selectivity in Electrochemical CO2 Reduction in Competition with Hydrogen Evolution Employing Manganese Bipyridine Complexes.

Selective reduction of CO2 is an efficient solution for producing nonfossil-based chemical feedstocks and simultaneously alleviating the increasing atmospheric concentration of this greenhouse gas. With this aim, molecular electrocatalysts are being extensively studied, although selectivity remains an issue. In this work, a combined experimental-computational study explores how the molecular structure of Mn-based complexes determines the dominant product in the reduction of CO2 to HCOOH, CO, and H2. In contrast to previous Mn(bpy-R)(CO)3Br catalysts containing alkyl amines in the vicinity of the Br ligand, here, we report that bpy-based macrocycles locking these amines at the side opposite to the Br ligand change the product selectivity from HCOOH to H2. Ab initio molecular dynamics simulations of the active species showed that free rotation of the Mn(CO)3 moiety allows for the approach of the protonated amine to the reactive center yielding a Mn-hydride intermediate, which is the key in the formation of H2 and HCOOH. Additional studies with DFT methods showed that the macrocyclic moiety hinders the insertion of CO2 to the metal hydride favoring the formation of H2 over HCOOH. Further, our results suggest that the minor CO product observed experimentally is formed when CO2 adds to Mn on the side opposite to the amine ligand before protonation. These results show how product selectivity can be modulated by ligand design in Mn-based catalysts, providing atomistic details that can be leveraged in the development of a fully selective system.

Directed Photochemically Mediated Nickel-Catalyzed (Hetero)arylation of Aliphatic C-H Bonds.

Site-selective functionalization of unactivated C(sp3)-H centers is challenging because of the ubiquity and strength of alkyl C-H bonds. Herein, we disclose a position-selective C(sp3)-C(sp2) cross-coupling reaction. This process engages C(sp3)-H bonds and aryl bromides, utilizing catalytic quantities of a photoredox-capable molecule and a nickel precatalyst. Using this technology, selective C-H functionalization arises owing to a 1,6-hydrogen atom transfer (HAT) process that is guided by a pendant alcohol-anchored sulfamate ester. These transformations proceed directly from N-H bonds, in contrast to previous directed, radical-mediated, C-H arylation processes, which have relied on prior oxidation of the reactive nitrogen center in reactions with nucleophilic arenes. Moreover, these conditions promote arylation at secondary centers in good yields with excellent selectivity.