Oxidative Cleavage Research Articles

Comprehensive assessment of sludge wet air oxidation and its combination with anaerobic digestion

Wet air oxidation (WAO) is a promising sludge treatment technology but has yet to be used widely. This study evaluates a new integrated pathway of AD plus WAO, juxtaposing against the standalone AD and WAO, from the aspects of carbon emissions, energy efficiency, and cost-benefits. The assessment unit is 1 t dewatered sludge with a water content of 80%, and the greenhouse gases are converted to equivalent CO2. WAO can recover the thermal heat released from organic oxidation, resulting in the lowest carbon emissions, 10.92 to −36.86 kg CO2-eq/t. AD plus WAO also performs well with 32.21 to −48.16 kg CO2-eq/t. All three ways can produce renewable energy through biogas utilization or thermal recovery. WAO has the highest energy efficiency of 35%–42% due to efficient thermal energy recovery, and AD plus WAO has a second-ranked efficiency of 15%–30%. However, WAO needs expensive facilities and external electricity, resulting in a higher expenditure than AD. The integrated systems also require a high investment, but can simplify digested sludge treatment. According to the normalized scores in the three aspects, WAO is recommended chiefly, especially for treating low-organic-content sludge. AD plus WAO ranked second and can be used for high-organic-content sludge.

Surface- and substrate-coated catalytic membrane for mitigating interference of water matrix species in intensified micropollutant confinement oxidation

The integration of advanced oxidation processes (AOPs) with membrane technology offers benefits for catalyst recovery and reducing membrane fouling. However, the application of the hybrid process could be hampered by the background species in water matrix. This study addresses this challenge by developing catalytic ceramic membranes (CCMs) with dual mechanisms to intensify acetaminophen (ACT) removal in water. The CCMs effectively activated peroxymonosulfate (PMS), achieving ACT degradation of 85% and 93% in real water matrices (reverse osmosis retentate and settled water, respectively) and 99% in MQ water. The CCMs demonstrated consistent performance across multiple operational cycles, even in the presence of humic acid (HA) (96% ACT reduction). The CCM design features Co3O4 catalytic layer on CCM surface, facilitating surface oxidation, reducing fouling, and TiO2 intermediate rejection layers serving as barrier for bulk organic pollutants, achieving 50% HA removal through rejection and 70% with 1.5mM PMS. This design facilitates catalytic degradation at the membrane surface, allowing retention and degradation of bulk organic pollutants and intermediates, while ACT permeates into CCM substrate. The surface oxidation and rejection enhanced confinement oxidation within the Co3O4-coated macropores, minimizing interference from background species. LC-QTOF analysis identified multiple degradation pathways, including hydroxylation, acetyl-amino group cleavage, side chain oxidation and benzene ring cleavage, with intermediates showing reduced toxicity. Reactive oxygen species involved in the system were identified and PMS activation mechanism was proposed. This research highlights the potential of the hybrid process, enhancing micropollutant removal by mitigating interference from background species, providing practical implications in water treatment applications.

Synthetic studies on fusicoccin A: Enantioselective synthesis of the C-ring fragment

The enantioselective synthesis of the C-ring fragment of fusicoccin A is described. The TBS ether of hydroxyketone prepared by baker’s yeast reduction was converted to the α-ethylidene ketone by aldol condensation with propionaldehyde, followed by Michael reaction with divinylcopper reagent and conversion to enol triflate to afford a single diastereomer. X-ray crystallographic analysis of the crystalline derivative of the single diastereomer showed that the asymmetric carbon formed by the Michael reaction was consistent with the configuration of the C15 asymmetric carbon of fusicoccin A. The vinyl group of the enol triflate was converted to a hydroxymethyl group by selective dihydroxylation with a bulky ligand, oxidative cleavage of the resultant 1,2-diol with lead tetraacetate, and DIBAL-H reduction. The hydroxymethyl group was subsequently converted to TBS ether, followed by the hydrogenolysis of the benzyl group and Dess–Martin oxidation, accomplishing the enantioselective synthesis of the desired C-ring fragment of fusicoccin A.

Enhancement of Selective Catalytic Oxidation of Lignin β‐O‐4 Bond via Orbital Modulation and Surface Lattice Reconstruction

The orbital modulation and surface lattice reconstruction represent an effective strategy to regulate the interaction between catalyst interface sites and intermediates, thereby enhancing catalytic activity and selectivity. In this study, the crystal surface of Au‐K/CeO2 catalyst can undergo reversible transformation by tuning the coordination environment of Ce, which enables the activation of the Cβ‐H bond and the oxidative cleavage of the Cβ‐O and Cα‐Cβ bonds, leading to the cleavage of 2‐phenoxy‐1‐phenylethanol. The t2g orbitals of Au 5d hybridize with the 2p orbitals of lattice oxygen in CeO2 via π‐coordination, modulating the coordination environment of Ce 4f and reconstructing the lattice oxygen in the CeO2 framework, as well as increasing the oxygen vacancies. The interface sites formed by the synergy between Au clusters in the reconstructed Ce‐OL1‐Au structure and doped K play dual roles. On the one hand, it activates the Cβ‐H bond, facilitating the enolization of the pre‐oxidized 2‐phenoxy‐1‐phenylethanone. On the other hand, through single‐electron transfer involving Ce3+ 4f1 and the adsorption by oxygen vacancies, it enhances the oxidative cleavage of the Cβ‐O and Cα‐Cβ bonds. This study elucidates the complex mechanistic roles of the structure and properties of Au‐K/CeO2 catalyst in the selective catalytic oxidation of lignin β‐O‐4 bond.

Tissue-specific alternative splicing and the functional differentiation of LmLPMO15-1 in Locusta migratoria.

Insect lytic polysaccharide monooxygenases (LPMO15s) are newly discovered copper-dependent enzymes that promote chitin degradation in insect through oxidative cleavage of glycosidic bonds. They are potential pesticide targets due to their critical role for chitin turnover in the integument, trachea, and peritrophic matrix of the midgut during insect molting. However, the knowledge about whether and how LPMO15s participate in chitin turnover in other tissues is still insufficient. Here, using the orthopteran pest Locusta migratoria as a model, a novel alternative splicing site of LmLPMO15-1 was discovered and it produces 2 variants, LmLPMO15-1a and LmLPMO15-1b. The transcripts of LmLPMO15-1a and LmLPMO15-1b were specifically expressed in the trachea and foregut, respectively. RNA interference targeting LmLPMO15-1 (a common fragment shared by both LmLPMO15-1a and LmLPMO15-1b), a specific region of LmLPMO15-1a or LmLPMO15-1b all significantly reduced survival rate of nymphs and induced lethal phenotypes with developmental stasis or molt failure. Ultrastructure analysis demonstrated that LmLPMO15-1b was specifically involved in foregut old cuticle degradation, while LmLPMO15-1a was exclusively responsible for the degradation of the tracheal old cuticle. This study revealed LmLPMO15-1 achieved tissue-specific functional differentiation through alternative splicing, and proved the significance of the spliced variants during insect growth and development. It provides new strategies for pest control targeting LPMO15-1.

The Anti-Cancer Stem Cell Properties of Copper(II)-Terpyridine Complexes with Attached Salicylaldehyde Moieties.

We report the synthesis, characterisation, and anti-breast cancer stem cell (CSC) properties of two copper(II)-terpyridine complexes with bidentate salicylaldehyde moieties (2-hydroxybenzaldehyde for 1 and 2-hydroxy-1-naphthaldehyde for 2). The copper(II)-terpyridine complexes 1 and 2 are stable in biologically relevant aqueous solutions and display micromolar potency towards breast CSCs. The most effective complex 1 is 5-fold and 6.6-fold more potent towards breast CSCs than salinomycin and cisplatin, respectively. The copper(II)-terpyridine complexes 1 and 2 also decrease the formation and viability of three-dimensionally cultured mammospheres within the micromolar range. Notably complex 1 is up to 7-fold more potent towards mammospheres than salinomycin or cisplatin. Mechanistic studies suggest that the copper(II)-terpyridine complexes 1 and 2 are able to readily enter breast CSCs, elevate intracellular reactive oxygen species levels, induce DNA damage (presumably by oxidative DNA cleavage), and evoke apoptosis that is independent of caspases. This study shows that the copper(II)-terpyridine motif is a useful building block for the design of anti-breast CSC agents and reinforces the therapeutic potential of copper coordination complexes.

Recent Advances in Rechargeable Zn-Air Batteries

Rechargeable Zn-air batteries are considered to be an effective energy storage device due to their high energy density, environmental friendliness, and long operating life. Further progress on rechargeable Zn-air batteries with high energy density/power density is greatly needed to satisfy the increasing energy conversion and storage demands. This review summarizes the strategies proposed so far to pursue high-efficiency Zn-air batteries, including the aspects of the electrocatalysts (from noble metals to non-noble metals), the electrode chemistry (from the oxygen evolution reaction to the organic oxidation reaction), electrode engineering (from powdery to free-standing), aqueous electrolytes (from alkaline to non-alkaline) and the battery configuration (from liquid to flexible). An essential evaluation of electrochemistry is highlighted to solve the challenges in boosting the efficiency of rechargeable metal-air batteries. In the end, the perspective on current challenges and future research directions to promote the industrial application of rechargeable Zn-air batteries is provided.

Cover Feature: Oxidative Cleavage of α‐O‐4, β‐O‐4, and 4‐O‐5 Linkages in Lignin Model Compounds Over P, N Co‐Doped Carbon Catalyst: A Metal‐Free Approach (ChemSusChem 21/2024)

Cover Feature: Oxidative Cleavage of α‐O‐4, β‐O‐4, and 4‐O‐5 Linkages in Lignin Model Compounds Over P, N Co‐Doped Carbon Catalyst: A Metal‐Free Approach (ChemSusChem 21/2024)

Oxidative Cleavage of Aromatic C-O Linkages by Oxoammonium Salts.

Oxidative cleavage of aromatic C(sp2)-O bond is important to the conversion of biomass and plastic wastes into value-added chemicals. Here we put forward the oxidative cleavage of para-C-O bonds in phenolic compounds in use of oxoammonium salts as oxidant and water as the oxygen source. The mechanism is that oxoammonium cation activates water to form hydroxy-oxoammonium adduct and thus realizes the ipso-substitution of 4-alkoxyphenol, which is proved by substituent effect, isotope labelling experiments, and kinetic analysis. Furthermore, this protocol is successfully applied into the depolymerization of both lignin model compounds with α-O-5 and 4-O-5 linkages and polyphenylene oxide (PPO).

Electrochemical degradation of aromatic organophosphate esters: Mechanisms, toxicity changes, and ecological risk assessment

Aromatic organophosphate esters (AOPEs), including triphenyl phosphate (TPHP), tricresyl phosphate (TCP), and 2-ethylhexyl diphenyl phosphate (EHDPP), pose significant health and ecological risks. Electrochemical advanced oxidation process (EAOP) is effective in removing refractory pollutants. In this study, the degradation performance and detoxication ability of AOPEs by EAOP were investigated. Hydroxylation, oxidation, and bond cleavage products were identified as major degradation products (DPs) due to the reaction with ·OH and O₂·-. Toxicity assessments using ecological structure activity relationship (ECOSAR) model and flow cytometry (FCM) revealed the cytotoxicity and aquatic toxicity for DPs were significantly decreased. 16S rRNA gene sequencing of sediment exposure to AOPEs and DPs were applied to assess ecological toxicity, and results showed reduced bacterial richness and diversity with EHDPP and TCP, while TPHP slightly enhanced richness. AOPEs and DPs altered bacterial genera involved in carbon, nitrogen, sulfur cycling and organic compound degradation. Bacterial community assembly suggested elevated stochastic processes and reduced ecotoxicity, confirming AOPEs can be effectively detoxified by 10-min EAOP treatment. Molecular ecological network analysis indicated increased complexity and stability of bacterial communities with DPs. These findings comprehensively revealed the toxicity of AOPEs and their DPs and provided the first evidence of effective degradation and detoxification by EAOP from ecotoxicological perspective.

Radiolytic support for oxidative metabolism in an ancient subsurface brine system

Abstract Long-isolated subsurface brine environments (Ma-Ga residence times) may be habitable if they sustainably provide substrates, e.g. through water-rock reaction, that support microbial catabolic energy yields exceeding maintenance costs. The relative inaccessibility and low biomass of such systems has led to limited understanding of microbial taxonomic distribution, metabolism, and survival under abiotic stress exposure in these extreme environments. In this study, taxonomic and metabolic annotations of 95 single cell amplified genomes (SAGs) were obtained for one low biomass (103–104 cells/mL), hypersaline (246 g/L), radiolytically enriched brine obtained from 3.1 km depth in South Africa’s Moab Khotsong mine. The majority of SAGs belonged to three halophilic families (Halomondaceae (58%), Microbacteriaceae (24%), and Idiomarinaceae (8%)) and did not overlap with any family-level identifications from service water or a less saline dolomite aquifer sampled in the same mine. Functional annotation revealed complete metabolic modules for aerobic heterotrophy (organic acids and xenobiotics oxidation), fermentation, denitrification and thiosulfate oxidation, suggesting metabolic support in a microoxic environment. SAGs also contained complete modules for degradation of complex organics, amino acid and nucleotide synthesis, and motility. This work highlights a long-isolated subsurface fluid system with microbial metabolism fueled by radiolytically generated substrates, including O2, and suggests subsurface brines with high radionuclide concentrations as putatively habitable and redox-sustainable environments over long (ka-Ga) timescales.

Heteropolyacids promoted NiMo/MOF catalyst for catalytic oxidation of lignin dimers in oxygen atmosphere

Lignin, as an important biomass resource, has significant research value in its oxidative cleavage process. Nickel-based metal catalysts could selectively depolymerize lignin. A series of heteropolyacid doped nickel based bimetallic catalysts Ni4Mo1-MOF-x（x represented heteropolyacid）were prepared by hydrothermal method, which were calcined to catalyze the oxidative cleavage of lignin model compound (2-phenoxy-1-acetophenone). The catalyst Ni4Mo1-MOF-SiWA-0.1(500) showed the best catalytic performance in methanol solvent under conditions of 160 °C, 4 h, 0.5 MPa oxygen pressure, where the conversion rate was nearly 100 % and the yields of phenol and benzoic acid were 54.5 % and 23.3 %, respectively. The catalysts were well characterized to explore the catalytic performance during the oxidation of lignin dimer. This study could provide some interesting and useful information for the catalytic oxidation of lignin to biomass-derived chemicals.

Optimization of Antiproliferative Properties of Triimine Copper(II) Complexes.

Cu(II) complexes with 2,2':6',2″-terpyridines (terpy) and 2,6-bis(thiazol-2-yl)pyridines (dtpy) with 1- or 2-naphtyl and methoxy-naphtyl were synthesized to elucidate the impact of the triimine core, naphtyl linking mode, and presence of methoxy groups on the antiproliferative activity of [CuCl2(Ln)]. Their antiproliferative effect was analyzed in ovarian (A2780) and colorectal (HCT116) carcinomas and colorectal carcinoma resistant to doxorubicin (HCT116-DoxR) cell lines and in normal human fibroblasts. Among all complexes, the 1- and 2-naphtyl substituted terpy Cu(II) complexes (Cu1a and Cu1b) showed the strongest cytotoxicity, namely, in HCT116-DoxR 2Dcells and were also capable of inducing the loss of cell viability in 3D HCT116-DoxR spheroids. Their intracellular localization, capability to increase reactive oxygen species (ROS), and interaction with DNA (nonintercalative mode) trigger oxidative DNA cleavage leading to cell death by apoptosis and autophagy. Cu1a and Cu1b do not show in vivo toxicity in a chicken embryo and can interact with bovine serum albumin (BSA).

Photoinduced Bartoli Indole Synthesis by the Oxidative Cleavage of Alkenes with Nitro(hetero)arenes

Given the unique charm of dipole chemistry, intercepting N‐O=C dipoles precisely generated by designed processes to develop novel reactivity has become a seminal challenge. The polar fragmentation of 1,3,2‐dioxazolidine species generated through the radical addition of excited nitro(hetero)arenes to alkenes represents a significantly underappreciated mechanism for generating N‐O=C dipoles. Herein, we present a photoinduced Bartoli indole synthesis by the oxidative cleavage of alkenes with nitro(hetero)arenes. Various indoles and azaindoles are constructed through the multi‐step spontaneous rearrangement of carbonyl imine intermediates generated by the polar fragmentation of 1,3,2‐dioxazolidine species. Mechanism studies and DFT calculations support that the reaction involves radical cycloaddition, ozonolysis‐type cycloreversion, intramolecular H‐shift of carbonyl imines, and 3,3‐sigmatropic shift of O‐Alkenyl hydroxylamines, etc. The implementation of continuous‐ flow photochemistry, in particular, significantly enhances efficiency, thereby overcoming obstacles to the commercialization process.

Visible Light-Driven Selective Oxidative Transformation of Vicinal Diols Using ZnS-Based Photocatalyst in the Presence of Molecular Oxygen

The heterogeneous photocatalysis for the oxidative cleavage of C-C bond is significant to the transformation of biomass feedstock. In this work, a heterojunction photocatalyst based on the conductor ZnS and g-C3N4 (CN) material is prepared and employed in the aerobic oxidative cleavage reaction of vicinal diol under visible light irradiations. As a result, it is found that 3ZnS/CN catalyst obtained by a mechanical grinding method shows a high photocatalytic activity. In the photocatalytic oxidative cleavage process of 1-phenyl-1, 2-glycol, more than 98.7% conversion of substrate with a 96.2% selectivity of benzaldehyde was attained using O2 as oxidant. In addition, the photocatalyst recycling experiments exhibited that the 3ZnS/CN catalyst still kept a good activity and stability even after being recycled for 5 times. Finally, the active reaction intermediates are investigated by the control experiments and the relative EPR detection. According to the obtained results and photocatalytic principle, the mechanism for the selective oxidative transformatioin of 1-phenyl-1, 2-glycol has been proposed. It gives a promising approach for the catalytic utilization of biomass-based lignin and cellulose.

Kinetic Insights into Solar-Assisted Fabrication and Photocatalytic Performance of CoWO4/NCW Heterostructure

This work studies the kinetic model for the solar-driven fabrication of CoWO4/NCW heterostructure photocatalysts and investigates their enhanced photocatalytic degradation activity. The synthesis of CoWO4/NCW, its characterization, and the kinetic aspects of photocatalytic degradation under solar light. New nanocomposite prepared from Nano cellulose (NCW) by hydrolysis cotton waste (CW) by nitric acid and cobalt tungstate (CoWO4) prepared from sodium tungstate and cobalt chloride by wet chemical method and characterized through XRD, FTIR, EDX, and FE-SEM analyses. The composite's performance in organic oxidation from refinery wastewater (RWW) was evaluated under solar light. The high removal ratio was 97.4% for organic pollutants (OP) in refinery wastewater. The results indicate that the heterostructure exhibits improved photocatalytic performance compared to individual components, which kinetics model was the best to represent the photocatalytic degradation of organic pollutants from oily wastewater over the heterostructure CoWO4/NCW catalyst. Add future applications of this finding in the relevant industries. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Templated synthesis of holy MIL-125(Ti) for the boosted photocatalytic performance in volatile organic compound oxidation and water treatment

This study presents the synthesis of hierarchically porous holy MIL-125(Ti) (H-MIL-125(Ti)) photocatalyst via a polystyrene (PS)-directed templating approach combined with solvent evaporation self-assembly (SESA). Sacrificial PS microsphere templates facilitated the formation of a macroporous structure, acting as temporary placeholders during metal–organic frameworks (MOF) crystallization. Removal of the templates created a complementary porous network within MIL-125(Ti), yielding a hierarchical pore architecture comprising inherent micropores and templated macropores. Characterization techniques revealed a high surface area (1204 m2 L−1) and optimal band gap (3.2 eV). Photoelectrochemical studies demonstrated efficient charge carrier generation and separation, with high average photocurrent density (4.5 mA cm−2) and low charge transfer resistance (27.5 Ω cm2). H-MIL-125(Ti) exhibited excellent photocatalytic activity for degrading various (volatile)organic pollutants under visible light, highlighting the importance of rational design and synthesis strategies in optimizing the performance of advanced porous materials.

Ex Situ Electro‐Organic Synthesis – A Method for Unrestricted Reaction Control and New Options for Paired Electrolysis

AbstractClassic in situ electro‐organic synthesis with substrates in an electrolyzer must compromise process conditions to balance electro‐ and thermochemical steps at both electrodes. This often restricts efficiency and product selectivity, since requirements may deviate for electrochemical (catalyst activation) and chemical (organic synthesis) steps, as well as for paired anode‐ and cathode reactions. Breaking this barrier, we report ex situ electro‐organic synthesis as a versatile method that enables unique product selectivity and unusual product pairs. We exemplify the concept for pairing H2 evolution (HER) with anodic alcohol oxidation. The two‐step method accomplishes this by separating cathode reactions from organic substrate oxidation, and anodic electrocatalyst activation from chemical conversion of organic substrates in time and space. First, the electro‐oxidation of Ni(OH)2 anodes to NiOOH is paired with H2 production by alkaline water electrolysis. Then, “charged” NiOOH electrodes are removed from the electrolyzer and used in external vessels to oxidize model substrate benzyl alcohol under regeneration of Ni(OH)2. Free choice of reaction media outside the electrolyzer allows to selectively obtain benzoic acid (in water) or benzaldehyde (in n‐hexane), whereas classic in situ electrosynthesis only produces the acid together with H2. Perspectively, the method enables electrosynthesis of previously inaccessible products paired to H2 generation.

Evaluation of Active Oxygen Species Derived from Water Splitting for Electrocatalytic Organic Oxidation

AbstractActive oxygen species (OH*/O*) derived from water electrolysis are essential for the electrooxidation of organic compounds into high‐value chemicals, which can determine activity and selectivity, whereas the relationship between them remains unclear. Herein, using glycerol (GLY) electrooxidation as a model reaction, we systematically investigated the relationship between GLY oxidation activity and the formation energy of OH* (ΔGOH*). We first identified that OH* on Au demonstrates the highest activity for GLY electrooxidation among various pure metals, based on experiments and density functional theory, and revealed that ΔGOH* on Au‐based alloys is influenced by the metallic composition of OH* coordination sites. Moreover, we observed a linear correlation between the adsorption energy of GLY (Eads) and the d‐band center of Au‐based alloys. Comprehensive microkinetic analysis further reveals a volcano relationship between GLY oxidation activity, the ΔGOH* and the adsorption free energy of GLY (ΔGads). Notably, Au3Pd and Au3Ag alloys, positioned near the peak of the volcano plot, show excellent activity, attributed to their moderate ΔGOH* and ΔGads, striking a balance that is neither too high nor too low. This research provides theoretical insights into modulating active oxygen species from water electrolysis to enhance organic electrooxidation reactions.

Anthropogenic Extremely Low Volatility Organics (ELVOCs) Govern the Growth of Molecular Clusters Over the Southern Great Plains During the Springtime

AbstractNew particle formation (NPF) often drives cloud condensation nuclei concentrations and the processes governing nucleation of molecular clusters vary substantially in different regions. The growth of these clusters from ∼2 to >10 nm diameters is often driven by the availability of extremely low volatility organic vapors (ELVOCs). Although the pathways to ELVOC formation from the oxidation of biogenic terpenes are better understood, the mechanistic pathways for ELVOC formation from oxidation of anthropogenic organics are less well understood. We integrate measurements and detailed regional model simulations to understand the processes governing NPF and secondary organic aerosol formation at the Southern Great Plain (SGP) observatory in Oklahoma and compare these with a site within the Bankhead National Forest (BNF) in Alabama, southeast USA. During our two simulated NPF event days, nucleation rates are predicted to be at least an order of magnitude higher at SGP compared to BNF largely due to lower sulfuric acid (H2SO4) concentrations at BNF. Among the different nucleation mechanisms in WRF‐Chem, we find that the dimethylamine (DMA) + H2SO4 nucleation mechanism dominates at SGP. We find that anthropogenic ELVOCs are critical for explaining the growth of particles observed at SGP. Treating organic particles as semisolid, with strong diffusion limitations for organic vapor uptake in the particle phase, brings model predictions into closer agreement with observations. We also simulate two non‐NPF event days observed at the SGP site and show that low‐level clouds reduce photochemical activity with corresponding reductions in H2SO4 and anthropogenic ELVOC concentrations, thereby explaining the lack of NPF.