O2 Species Research Articles

Single-Atom Zinc Sites with Synergetic Multiple Coordination Shells for Electrochemical H2 O2 Production.

Precise manipulation of the coordination environment of single-atom catalysts (SACs), particularly the simultaneous engineering of multiple coordination shells, is crucial to maximize their catalytic performance but remains challenging. Herein, we present a general two-step strategy to fabricate a series of hollow carbon-based SACs featuring asymmetric Zn-N2 O2 moieties simultaneously modulated with S atoms in higher coordination shells of Zn centers (n≥2; designated as Zn-N2 O2 -S). Systematic analyses demonstrate that the synergetic effects between the N2 O2 species in the first coordination shell and the S atoms in higher coordination shells lead to robust discrete Zn sites with the optimal electronic structure for selective O2 reduction to H2 O2 . Remarkably, the Zn-N2 O2 moiety with S atoms in the second coordination shell possesses a nearly ideal Gibbs free energy for the key OOH* intermediate, which favors the formation and desorption of OOH* on Zn sites for H2 O2 generation. Consequently, the Zn-N2 O2 -S SAC exhibits impressive electrochemical H2 O2 production performance with high selectivity of 96 %. Even at a high current density of 80 mA cm-2 in the flow cell, it shows a high H2 O2 production rate of 6.924 mol gcat -1 h-1 with an average Faradaic efficiency of 93.1 %, and excellent durability over 65 h.

Porous Molybdenum Nitride Nanosphere as Carrier-Free and Efficient Nitric Oxide Donor for Synergistic Nitric Oxide and Chemo/Sonodynamic Therapy.

Given its abundant physiological functions, nitric oxide (NO) has attracted much attention as a cancer therapy. The sensitive release and great supply capacity are significant indicators of NO donors and their performance. Here, a transition metal nitride (TMN) MoN@PEG is adopted as an efficient NO donor. The release process starts with H+-triggered denitrogen owing to the high electronegativity of the N atom and weak Mo-N bond. Then, these active NHx are oxidized by O2 and other reactive oxygen species (ROS) to form NO, endowing specific release to the tumor microenvironment (TME). With a porous nanosphere structure (80 nm), MoN@PEG does not require an extra carrier for NO delivery, contributing to ultrahigh atomic utilization for outstanding release ability (94.1 ± 5.6 μM). In addition, it can also serve as a peroxidase and sonosensitizer for anticancer treatment. To further improve the charge separation, MoN-Pt@PEG was prepared to enhance the sonodynamic therapy (SDT) effect. Accordingly, ultrasound (US) further promotes NO generation due to more ROS generation, facilitating in situ peroxynitrite (·ONOO-) generation with great cytotoxicity. At the same time, the nanostructure also degrades gradually, leading to high elimination (94.6%) via feces and urine within 14-day. The synergistic NO and chemo-/sono-dynamic therapy brings prominent antitumor efficiency and further activates the immune response to inhibit metastasis and recurrence. This work develops a family of NO donors that would further widen the application of NO therapy in other fields.

Water-Promoted Carbon-Carbon Bond Cleavage Employing a Reusable Fe Single-Atom Catalyst.

The development of methods for selective cleavage reactions of thermodynamically stable C-C/C=C bonds in a green manner is a challenging research field which is largely unexplored. Herein, we present a heterogeneous Fe-N-C catalyst with highly dispersed iron centers that allows for the oxidative C-C/C=C bond cleavage of amines, secondary alcohols, ketones, and olefins in the presence of air (O2 ) and water (H2 O). Mechanistic studies reveal the presence of water to be essential for the performance of the Fe-N-C system, boosting the product yield from <1 % to >90 %. Combined spectroscopic characterizations and control experiments suggest the singlet 1 O2 and hydroxide species generated from O2 and H2 O, respectively, take selectively part in the C-C bond cleavage. The broad applicability (>40 examples) even for complex drugs as well as high activity, selectivity, and durability under comparably mild conditions highlight this unique catalytic system.

Characterization of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particles (PM2.5) in the North China Plain using positive-ion atmospheric pressure photoionization (APPI) coupled with fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS)

Many aromatic compounds, including 16 types of U.S. EPA priority PAHs, exist in substituted or unsubstituted forms and have high toxicities. Aromatic compounds in aerosols collected in the North China Plain (NCP) were characterized by GC-MS and atmospheric pressure photoionization (APPI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). The concentrations of the 16 types of PAHs in the collected samples ranged from 277.0 to 876.8 ng/m3, which were higher than those collected in other regions and countries. Previous studies reported that only 27 wt% of aromatic compounds could be eluted using the GC system and demonstrated that APPI FT-ICR MS is a useful method for identifying large-molecular aromatics. In this study, two samples collected from the NCP were successfully characterized by APPI FT-ICR MS. In the APPI + mode, 231 and 228 CH formulas (containing only C and H and having a double bond equivalent (DBE) of 4 or greater) were identified, accounting for 10% of the numerical fraction and more than 40% of the intensity fraction. The FT-ICR data revealed that condensed PAHs with 6–8 aromatic rings had relatively high abundances and that a series of PAH homologs (alkylated PAHs) with identical DBE values ranging from 4 to 30 were present. Furthermore, heteroatom groups were also identified as significant components of the aromatic fractions. The O1, O2, N1, NO2, and S1 class species with DBE values of 3–34 and carbon numbers of 11–42 were identified by APPI FT-ICR MS. The heteroatom PAHs had DBE values and carbon number distributions similar to regular PAHs. The aromatic fractions determined in this work provide useful data for future quantitative analyses of aromatic compounds with high toxicities and our findings will help improve the current understanding of PAH compositions in the northern China. However, further research is needed to determine the abundances and toxicities of various apparent or substituted PAHs outside of the 16 types identified by the U.S. EPA as priority PAH compounds, which have been extensively researched.

Climate, Oxygen, and the Future of Marine Biodiversity.

The ocean enabled the diversification of life on Earth by adding O2 to the atmosphere, yet marine species remain most subject to O2 limitation. Human industrialization is intensifying the aerobic challenges to marine ecosystems by depleting the ocean's O2 inventory through the global addition of heat and local addition of nutrients. Historical observations reveal an ∼2% decline in upper-ocean O2 and accelerating reports of coastal mass mortality events. The dynamic balance of O2 supply and demand provides a unifying framework for understanding these phenomena across scales from the global ocean to individual organisms. Using this framework, we synthesize recent advances in forecasting O2 loss and its impacts on marine biogeography, biodiversity, and biogeochemistry. We also highlight three outstanding uncertainties: how long-term global climate change intensifies ocean weather events in which simultaneous heat and hypoxia create metabolic storms, how differential species O2 sensitivities alter the structure of ecological communities, and how global O2 loss intersects with coastal eutrophication. Projecting these interacting impacts on future marine ecosystems requires integration of climate dynamics, biogeochemistry, physiology, and ecology, evaluated with an eye on Earth history. Reducing global and local impacts of warming and O2 loss will be essential if humankind is to preserve the health and biodiversity of the future ocean.

Structural and Functional Diversity of the Peroxiredoxin 6 Enzyme Family.

Significance: Peroxiredoxins (Prdxs) with a single peroxidative cysteine (CP) in a conserved motif PXXX(T/S)XXCP within its thioredoxin fold, have been classified as the peroxiredoxin 6 (Prdx6 ) family. All Prdxs can reduce H2O2 and short chain hydroperoxides while Prdx6 in addition, can reduce phospholipid hydroperoxides (PLOOH) due to its ability to interact with peroxidized phospholipid substrate. The single CP of Prdx6 uses various external electron donors including glutathione thioredoxin, and ascorbic acid for resolution of its peroxidized state and, therefore, its peroxidase activity. Prdx6 proteins also exhibit Ca2+-independent phospholipase A2 (PLA2), lysophosphatidylcholine acyltransferase (LPCAT), and chaperone activities that depend on cellular localization and the oxidation and oligomerisation states of the protein. Thus, Prdx6 is a "moonlighting" enzyme. Recent Advance: Physiologically, Prdx6s have been reported to play an important role in protection against oxidative stress, repair of peroxidized cell membranes, mammalian lung surfactant turnover, activation of some NADPH oxidases, the regulation of seed germination in plants, as an indicator of cellular levels of reactive O2 species through Nrf-Klf9 activation, and possibly in male fertility, regulation of cell death through ferroptosis, cancer metastasis, and oxidative stress-related signalling pathways. Critical Issues: This review outlines Prdx6 enzyme unique structural features and explores its wide range of physiological functions. Yet, existing structural data falls short of fully revealing all of human Prdx6 multifunctional roles. Further endeavour is required to bridge this gap in its understanding. Although there are wide variations in both the structure and function of Prdx6 family members in various organisms, all Prdx6 proteins show the unique a long C-terminal extension that is also seen in Prdx1, but not in other Prdxs. Future Directions: As research data continues to accumulate, the potential for detailed insights into the role of C-terminal of Prdx6 in its oligomerisation and activities. There is a need for thorough exploration of structural characteristics of the various biological functions. Additionally, uncovering the interacting partners of Prdx6 and understanding its involvement in signalling pathways will significantly contribute to a more profound comprehension of its role.

How Ligand Geometry Affects the Reactivity of Co(II) Cyclam Complexes

AbstractCobalt complexes are extensively studied as bioinspired models for non‐heme oxygenases as they facilitate both the stabilization and characterization of metal‐oxygen intermediates. As an analog to the well‐known Co(cyclam) complex Co{N4} (cyclam=1,4,8,11‐tetraazacyclotetradecane), the CoII complex Co{i‐N4} with the isomeric isocyclam ligand (isocyclam=1,4,7,11‐tetraazacyclotetradecane) was synthesized and characterized. Despite the identical N4 donor set of both complexes, Co{i‐N4} enables the 2e−/2H+ reduction of O2 with a lower overpotential (ηeff of 385 mV vs. 540 mV for Co{N4}), albeit with a diminished turnover frequency. Characterization of the intermediates formed upon O2 activation of Co{i‐N4} reveals a structurally identified stable μ‐peroxo CoIII dimer as the main product. A superoxo CoIII species is also formed as a minor product, as indicated by EPR spectroscopy. In further reactivity studies, the electrophilicity of these in situ generated Co−O2 species was demonstrated by the oxidation of the O−H bond of TEMPO−H (2,2,6,6‐tetramethylpiperidin‐1‐ol) via a H atom abstraction process. Unlike the known Co(cyclam), Co{i‐N4} can be employed in oxygen atom transfer reactions oxidizing triphenylphosphine to the corresponding phosphine oxide highlighting the impact of geometrical modifications of the ligand while preserving the ring size and donor atom set on the reactivity of biomimetic oxygen activating complexes.

SIRT6 deficiency in endothelial cells exacerbates oxidative stress by enhancing HIF1α accumulation and H3K9 acetylation at the Ero1α promoter.

SIRT6, an important NAD+ -dependent protein, protects endothelial cells from inflammatory and oxidative stress injuries. However, the role of SIRT6 in cardiac microvascular endothelial cells (CMECs) under ischemia-reperfusion injury (IRI) remains unclear. The HUVECs model of oxygen-glucose deprivation/reperfusion (OGD/R) was established to simulate the endothelial IRI in vitro. Endoplasmic reticulum oxidase 1 alpha (Ero1α) mRNA and protein levels in SIRT6-overexpressing or SIRT6-knockdown cells were measured by qPCR and Western blotting. The levels of H2 O2 and mitochondrial reactive oxygen species (ROS) were detected to evaluate the status of oxidative stress. The effects of SIRT6 deficiency and Ero1α knockdown on cellular endoplasmic reticulum stress (ERS), inflammation, apoptosis and barrier function were detected by a series of molecular biological experiments and functional experiments in vitro. Chromatin immunoprecipitation, Western blotting, qPCR, and site-specific mutation experiments were used to examine the underlying molecular mechanisms. Furthermore, endothelial cell-specific Sirt6 knockout (ecSirt6-/- ) mice were subjected to cardiac ischemia-reperfusion surgery to investigate the effects of SIRT6 in CMECs in vivo. The expression of Ero1α was significantly upregulated in SIRT6-knockdown endothelial cells, and high Ero1α expression correlated with the accumulation of H2 O2 and mitochondrial ROS. In addition, SIRT6 deficiency increased ERS, inflammation, apoptosis and endothelial permeability, and these effects could be significantly attenuated by Ero1α knockdown. The deacetylase catalytic activity of SIRT6 was important in regulating Ero1α expression and these biological processes. Mechanistically, SIRT6 inhibited the enrichment of HIF1α and p300 at the Ero1α promoter through deacetylating H3K9, thereby antagonizing HIF1α/p300-mediated Ero1α expression. Compared with SIRT6-wild-type (SIRT6-WT) cells, cells expressing the SIRT6-H133Y-mutant and SIRT6-R65A-mutant exhibited increased Ero1α expression. Furthermore, ecSirt6-/- mice subjected to ischemia-reperfusion surgery exhibited increased Ero1α expression and ERS in CMECs and worsened injuries to microvascular barrier function and cardiac function. Our results revealed an epigenetic mechanism associated with SIRT6 and Ero1α expression and highlighted the therapeutic potential of targeting the SIRT6-HIF1α/p300-Ero1α axis.

Expert Insights: Phase III Clinical Trials in Non-Transfusion-Dependent (ENERGIZE) and Transfusion-Dependent (ENERGIZE-T) α- and β-Thalassaemia

The thalassaemias are a heterogeneous group of inherited chronic blood disorders associated with impaired haemoglobin (Hb) synthesis, resulting in ineffective erythropoiesis, haemolysis, and the development of lifelong anaemia. The pathophysiology of thalassaemia is due, in part, to increased energy demand to clear globin aggregates and reactive O2 species, and maintain overall red blood cell (RBC) health, coupled with insufficient adenosine triphosphate (ATP) production. For this article, interviews were conducted by EMJ in December 2022 with two key opinion leaders. Kevin Kuo is a Clinician-Investigator and Staff Haematologist at the University Health Network, Toronto, Canada, and Associate Professor in the Division of Hematology, Department of Medicine, University of Toronto, Canada. Maria Cappellini is Professor of Medicine in the Department of Clinical Sciences and Community, University of Milan, Italy. Both haematologists have over 50 years of expertise and clinical experience between them in treating patients with thalassaemia. The two experts provided insights into two ongoing Phase III clinical trials for both α- and β-thalassaemia. These trials are investigating the effect of mitapivat, a first-in-class, small molecule pyruvate kinase activator, in patients across the full range of thalassaemia subtypes. The ENERGIZE trial is investigating mitapivat in patients with non–transfusion-dependent thalassaemia (NTDT), and the ENERGIZE-T trial is investigating mitapivat in patients with transfusion-dependent thalassaemia (TDT).

Hydrogen Therapy and Its Future Prospects for Ameliorating COVID-19: Clinical Applications, Efficacy, and Modality.

Molecular hydrogen is renowned as an odorless and colorless gas. The recommendations developed by China suggest that the inhalation of hydrogen molecules is currently advised in COVID-19 pneumonia treatment. The therapeutic effects of molecular hydrogens have been confirmed after numerous clinical trials and animal-model-based experiments, which have expounded that the low molecular weight of hydrogen enables it to easily diffuse and permeate through the cell membranes to produce a variety of biological impacts. A wide range of both chronic and acute inflammatory diseases, which may include sepsis, pancreatitis, respiratory disorders, autoimmune diseases, ischemia-reperfusion damages, etc. may be treated and prevented by using it. H2 can primarily be inoculated through inhalation, by drinking water (which already contains H2), or by administrating the injection of saline H2 in the body. It may play a pivotal role as an antioxidant, in regulating the immune system, in anti-inflammatory activities (mitochondrial energy metabolism), and cell death (apoptosis, pyroptosis, and autophagy) by reducing the formation of excessive reactive O2 species and modifying the transcription factors in the nuclei of the cells. However, the fundamental process of molecular hydrogen is still not entirely understood. Molecular hydrogen H2 has a promising future in therapeutics based on its safety and possible usefulness. The current review emphasizes the antioxidative, anti-apoptotic, and anti-inflammatory effects of hydrogen molecules along with the underlying principle and fundamental mechanism involved, with a prime focus on the coronavirus disease of 2019 (COVID-19). This review will also provide strategies and recommendations for the therapeutic and medicinal applications of the hydrogen molecule.

Improving the efficiency of metal ions doped Fe2O3 nanoparticles: Photocatalyst for removal of organic dye from aqueous media

The metal ion-based nanocomposite photocatalysts were accepted to exhibit a wide range of photocatalytic and biological applications. In this paper, we synthesize bare Fe2O3, 1 wt% metal (Ag, Co, and Cu) doped Fe2O3 nanoparticles (NPs) using a simple hydrothermal process and wet impregnation method. The as-prepared nanomaterials crystalline structure, shape, optical characteristics, and elemental composition were determined by using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), Energy-dispersive X-ray (EDS) and Transmission electron microscopy (TEM) techniques. Furthermore, the synthesized nanocomposites were utilized as a photosensitizer for the degradation of reactive red (RR120) and orange II (O-II) dyes under sunlight irradiation. The synthesized 1 wt% Ag–Fe2O3 (AgF) NPs samples exhibit a more exceptional catalytic performance of RR120 and O-II dyes (98.32%) within 120 min than the existing Fe2O3, 1 wt% Co–Fe2O3, and Cu–Fe2O3 NPs. The effect of parameters such as exciton formation under solar irradiation, charge recombination rate, and surface charge availability. The metal oxide-doped nanocomposite economic relevance is revealed by their long-term durability and recyclability in photodegradation reactions. The photocatalytic investigations show that the active species O2∙−, HO∙ and h+ play an important role in the dye degradation process. This research might pave the opportunity for the sustainable development of greater photocatalysts for photodegradation and a wide range of environmental applications.

Strontium iron molybdenum oxide as electrocatalyst for nitrous oxide reduction in solid oxide fuel cells

Nitrous oxide (N2O) is an environmentally damaging gas and alternative methods for its abatement are needed. In this work, we developed an electrochemical route using the mixed ionic electronic conductor Sr2Fe1·5Mo0·5O6-δ (SFMO) as electrocatalyst for N2O reduction in the temperature range of 600–800 °C, at ambient pressure, for application in Solid Oxide Fuel Cells (SOFCs). The electrode mechanism, studied by electrochemical impedance spectroscopy (EIS), is discussed to involve a competition between both O2 and N2O species, particularly at lower temperatures, where N2O thermal decomposition is lower. In terms of electrocatalytic properties, galvanostatic transients were used to assess N2O electroreduction on the SFMO electrode. The results showed that, after cathodic polarization, the N2O conversion increases. In particular, a highest Faradaic efficiency (|Λ|) of 3.94 was obtained at 600 °C. The reversibility of the mechanism was also assessed, and the results showed that the reaction rate returns to its open circuit value upon current interruption. This work indicates, therefore, that the electrochemical promotion of N2O reduction can be an attractive tool to be implemented for the reduction of this environmentally damaging gas in SOFC systems.

P269 Proposed plan for oxygen therapy as an adjuvant to antibiotics in cystic fibrosis

Although the use of modulator treatments targeting the basal defect in the Cystic Fibrosis transmembrane conductance regulator improves lung function and is associated with reduced burden of lung infections, we have not seen bacterial eradication, thus antibiotic treatments remain crucial for targeting chronic Pseudomonas aeruginosa infection. Recent investigations have shown large zones of oxygen (O2) depletion in the infected part of CF lungs due to consumption of O2 by the surrounding neutrophils, where bacterial aerobic respiration is prevented. The restriction of O2 causes reduced uptake of antibiotics, down-regulation of antibiotic targets and inhibited induction of bactericidal amounts of reactive O2 species as seen for P. aeruginosa. By enhancing the aerobic physiology of the bacteria through adjuvant O2 treatment with normobaric O2 treatment (NBOT), the bacteria can be sensitized, and even clones, protected by the O2 depletion, can be treated. We hypothesize that adjuvant intermittent normobaric oxygenation (100% O2) has a beneficiary clinical impact on chronic P. aeruginosa lung infection.

Efficient degradation of cationic dyes by ZnO and ZnO–Fe(III) quantum dots under natural sunlight and UV light

Zinc oxide (ZnO) quantum dots (QDs) are very attractive to many applications due to their optical and electronic properties and low toxicity. Among the applications, ZnO has been applied to photocatalysis for degradation or organic pollutants. However, what is still not clear is the function of organic dyes that absorb in the visible region, when they are together with semiconductors known for their best photocatalytic performance in the UV region. Herein, the degradation efficiency of two cationic dyes under natural sunlight irradiation and UV light in the presence of ZnO and ZnO:Fe(III) QDs with the dopant at 0.02, 0.04, and 0.07 mol% was investigated. The QDs were prepared via sol-gel method in ethanol and the photocatalytic assays were carried out in the same environment. Fe(III)-doped ZnO QDs with 0.04 mol% gave the highest apparent rate constants with degradation percentage equal to 84.3% and 66.9%, for methylene blue (MB) and astrazon blue FGGL 300% (AB), respectively, after 7 min under sunlight irradiation. Experiments were carried out with scavengers for hydroxyl (⋅OH) and anion superoxide (O2−⋅) radicals, tert-butanol and 1,4-benzoquinone (1,4-BQ), respectively. MB degradation course did not change in the ethanolic medium, known as ⋅OH scavenger, as well as with an extra amount of tert-butanol. However, the photocatalytic efficiency strongly decreased under the presence of 1,4-BQ. Thus, it is assumed that the MB degradation route in ethanol occurs mainly through the radical species O2−⋅. The study proved to be very sustainable and eco-friendly, being carried out in an ethanolic environment and with natural sunlight. This strategy ensured maximum surface efficiency and photocatalytic activity.

Reaction characteristics of molten carbonate cell operated in fuel cell and electrolysis modes with reactant gas addition method

This work compares the electrode reaction mechanisms of 100 cm2 class molten carbonate cells (MCCs) operated in electrolysis cell (EC) and fuel cell (FC) modes using a reactant gas addition (RA) method. The RA method reveals essential information on an electrode reaction mechanism by measuring the overpotential of an electrode resulting from adding a reactant. The hydrogen electrode (HE) is revealed to be under a gas-phase mass transfer-controlled process in both modes. In addition, the HE overpotential at an inlet composition of H2: CO2: H2O = 0.3: 0.3: 0.4 atm is caused mainly by H2 species in FC mode, while CO2 contributes the majority in EC mode due to the production of H2 and consumption of CO2 by the water–gas shift reaction. On the other hand, most of the oxygen electrode (OE) overpotential is contributed by O2 species in both modes. The overpotential induced by O2 species was larger in FC mode than EC mode because EC mode generates O2 and provides less mass transfer resistance of O2 species in the liquid phase. The addition of CO2 to the OE raised overpotential in both modes. The overpotential was especially large in FC mode due to the reduced O2 partial pressure and relatively low in EC mode because of O2 generation. Therefore, the total overpotential in EC mode is less than in FC mode.

Computational Fluid Dynamics Analysis of a Hollow Fiber Membrane Module for Binary Gas Mixture

The membrane gas separation process has gained significant attention using the computational fluid dynamics (CFD) technique. This study considered the CFD method to find gas concentration profiles in a hollow fiber membrane (HFM) module to separate the binary gas mixture. The membrane was considered with a fiber thickness where each component’s mass fluxes could be obtained based on the local partial pressures, solubility, diffusion, and the membrane’s selectivity. COMSOL Multiphysics was used to solve the numerical solution at corresponding operating conditions and results were compared to experimental data. The two different mixtures, CO2/CH4 and N2/O2, were investigated to obtain concentration gradient and mass flux profiles of CO2 and O2 species in an axial direction. This study allows assessing the feed pressure’s impact on the HFM system’s overall performance. These results demonstrate that the increment in feed pressures decreased the membrane system’s separation performance. The impact of hollow fiber length indicates that increasing the active fiber length has a higher effective mass transfer region but dilutes the permeate-side purities of O2 (46% to 28%) and CO2 (93% to 73%). The results show that increasing inlet pressure and a higher concentration gradient resulted in higher flux through the membrane.

Robust chromophore-integrated MOFs as highly visible-white-light active and tunable size-selective photocatalysts towards benzothiazoles

Visible-light heterogeneous photocatalyst with high activity and selectivity is crucial for the development of organic transformations, but remains a formidable challenge. Herein, a simple and effective strategy was developed to integrate tetrazine moiety, a visible light active unit, into robust metal-organic frameworks (2D MOF-1(M), M = Co, Mn, Zn, and 3D MOF-2(Co)). MOF-1 series are isomorphous 2D porous frameworks, and MOF-2(Co) displays 3D porous framework. Interestingly, benefiting from the oxidative active species of O2•−, these MOFs all exhibit obviously highly enhanced photocatalytic activities toward the straightforward condensation of o-aminothiophenol and aromatic aldehydes at room temperature in EtOH under visible-white-light irradiation. Notably, compared to 3D MOF, the 2D layered MOF-1(Co) exhibited more excellent catalytic activity with a wide range of substrates possessing preeminent tolerance of steric hindrance. Most impressively, MOF-1(Co) can be recycled at least five times without significant loss of catalytic activity or crystallinity, exhibiting excellent stability and reusability. This study sheds light on the wide-ranging prospects of visible light active 2D MOFs as green photocatalysts for the preparation of fine chemicals

A combined approach toward enhancing 2-electron oxygen reduction through the incorporation of Pd-based complex into a carbonaceous matrix: Experimental and mechanistic-theoretical studies

The present work reports the development of a catalyst based on palladium (Pd) coordination compound covered and surrounded by Printex L6 (PL6C) carbon material and its application toward improving the selectivity and electrocatalysis involving the production of hydrogen peroxide via oxygen reduction reaction (2e–ORR). The morphology and structure of the Pd-based complex/PL6C catalyst were characterized by clusters of an average size of 2.4 µm composed of 1.3% (w/w) Pd2+ metal. Compared to the unmodified PL6C, the application of the Pd-based complex/PL6C led to a shift in the ORR onset potential by 250 mV vs Ag/AgCl 3 M to more positive potentials and 97% selectivity toward H2O2 production. This electrocatalytic effect was attributed to the π-π interactions between the dz2 orbital of the Pd2+ metal and the carbon close to the oxygenated functional groups present in the carbonaceous matrix. The mechanistic-theoretical analyses conducted showed that the oxygenated carboxyl functional group COOH is the group that favors most significantly the interaction between O2 and hydronium ions toward the formation of the OOH* species; the presence of the Pd2+ metal further contributes toward favoring this interaction. In addition, the Pd-based complex was found to influence the Laplacian of the electron density (V2ρ) for the bond between the carbon close to the COOH group and the oxygen atom of the ORR intermediates, and this facilitates the conversion of adsorbed O2 species into OOH* intermediates and increases the desorption capacity of the species from the active site, leading to H2O2 formation.

Singlet-excited dioxygen O2(a1Δg) and organic pollutants in marine waters beneath the Sun

The ground state dioxygen has a triplet spin state O2(X3Σg). The singlet excited O2(a1Δg) dioxygen possesses an excess energy of 22 kcal/mole and is highly reactive with respect to organic matter since all organic molecules have also singlet ground states with all spins paired; their reactions with O2(a1Δg) are not forbidden by spin selection. The chromophoric pollutants in sea waters under sun irradiation can generate O2(a1Δg) and other reactive oxygen species which could oxidase many wastes. This review describes mechanisms of O2(a1Δg) interaction with organic pollutants in seawater with black carbon dispersion and with corals.

Revealing the equilibrium relationship between lattice oxygen mobility and styrene removal: Sources of adsorption and activation by in situ experiments

Copper-manganese composite oxides have been extensively researched for the catalytic oxidation of volatile organic compounds (VOCs), but there is little understanding of the adsorption and activation of VOCs over these compounds. In this work, a series of amorphous Cu-Mn binary oxides with varying Cu/Mn ratios were prepared to explore their catalytic performance and the species involved in the adsorption and activation of styrene (C8H8). It was found that Cu1Mn5Ox demonstrated better catalytic activity among the four samples, better stability and water resistance due to the presence of more structural flaws, weaker Mn-O bonds and more surface lattice oxygen species. In situ designed experiments showed that the adsorbed oxygen species, O2, lattice oxygen, and copper species all played roles in the adsorption and activation of C8H8 at low temperatures. The degradation route for C8H8 was revealed by in situ DRIFTS, and benzoic acid decomposition was identified as the rate-limiting step of C8H8 degradation. This work provides a novel technique for regulating the synergistic adsorption and catalytic ability of amorphous bimetallic oxides to remove VOCs.