Catalytic Oxidation Research Articles

Pt nanoparticles in cooperation with Mn-P composite drive base-free selective oxidation of 5-hydroxymethylfurfural

Selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is a key approach to sustainable upgrading of furfural based biomass resources. In this work, small Pt nanoparticles (about 2.1 nm) loaded on MnPnOx composite were shown to effectively drive the base-free aerobic oxidation of HMF to FDCA in water. Regulating the P content in carrier enabled to tune HMF conversion and product distribution. The optimal Pt/MnP0.5Ox catalyst can reach 98% yield of FDCA at 110 °C under 10 bar of O2 after 24 h. It also showed the highest initial conversion rate of HMF (13 mmol molPt−1 s−1) and productivity of FDCA (4.1 mmol molPt−1 h−1) among all the Pt/MnPnOx catalysts. The carrier effect of P addition on promoting Pt oxidation catalysis was elucidated by using rigorous kinetic investigations and comprehensive characterizations. The initial conversion rate, rate constant and apparent activation energy were independently measured on oxidation of HMF and its derived intermediates. ICP-MS, XRD, TEM, H2-TPR, O2-TPD and XPS were used to acquire catalytic properties. It was demonstrated that P addition led to changes in carrier structure and metal-support interaction, which eventually promoted the formation of highly active electron-rich Pt0 sites and mobile reactive defect oxygen species. These features allowed improving the selective oxidation catalysis of supported-Pt nanoparticles for the base-free conversion of HMF to FDCA.

Nanoarchitectonics of hollow Co3O4 through tannic acid etching of ZIF-67 for catalysis of toluene oxidation

Oxide catalysts obtained by derivatization of MOFs as precursors often have excellent results in the catalysis of VOCs. In this study, the Co3O4 catalysts obtained by pyrolysis after tannic acid etching using ZIF-67 as precursor showed excellent toluene catalytic activity. Among them, Co3O4 −1–15 showed the best catalytic activity with T90 = 219 °C (the conversion temperatures of 90 %), which was 20 °C lower than that of Co3O4 -O obtained by direct pyrolysis of ZIF-67. It also exhibits excellent stability and cyclic stability. After tannic acid treatment, Co3O4 −1–15 exposed higher surface Co3+ and Olatt (surface lattice oxygen) content, which were the key factors for its most outstanding catalytic activity. Lattice oxygen mobility and oxygen vacancies were also important factors affecting catalyst activity.

A multifunctional N-GO/PtCo nanocomposite bridged carbon fiber interface for the electrochemical aptasensing of CA15-3 oncomarker

The development of integrated analytical devices is crucial for advancing next-generation point-of-care platforms. Herein, we describe a facile synthesis of a strongly catalytic and durable Nitrogen-doped graphene oxide decorated platinum cobalt (NGO-PtCo) nanocomposite that is conjugated with target-specific DNA aptamer (i-e. MUC1) and grown on carbon fiber. Benefitting from the combined features of the high electrochemical surface area of N-doped GO, high capacitance and stabilization by Co, and high kinetic performance by Pt, a robust, multifunctional, and flexible nanotransducer surface was created. The designed platform was applied for the specific detection of a blood-based oncomarker, CA15-3. The electrochemical characterization proved that nanosurface provides a highly conductive and proficient immobilization support with a strong bio-affinity towards MUC1 aptamer. The specific interaction between CA15-3 and the aptamer alters the surface properties of the aptasensor and the electroactive signal probe generated a remarkable increase in signal intensity. The sensor exhibited a wide dynamic range of 5.0 × 10−2 -200 U mL−1, a low limit of detection (LOD) of 4.1 × 10−2 U mL−1, and good reproducibility. The analysis of spiked serum samples revealed outstanding recoveries of up to 100.03 %, by the proposed aptasensor. The aptasensor design opens new revelations in the reliable detection of tumor biomarkers for timely cancer diagnosis.

Promotional effect of Sr modification on the catalytic oxidation of hydrogen chloride to chlorine over Cu/Y zeolite catalyst

Copper-based catalysts are regarded as highly promising catalysts for the oxidation of hydrogen chloride (HCl) to chlorine. This study involved the preparation of a range of copper-based catalysts via impregnation. The aim was to investigate the impact of Sr loading on the conversion rate of HCl in Cu/Y zeolite catalysts, through experimental analysis. The physicochemical properties of the catalyst were investigated using a series of characterization techniques. The experiment validated that the addition of Sr could improve the catalytic activity of Cu/Y zeolite catalyst and reduce the catalytic reaction temperature. The HCl conversion rate exceeded 89 %, with a spatial–temporal yield of approximately 2.75 gCl2gcat-1h-1 when the Sr loading amount was 1.5 %. The characterization results indicated that the addition of Sr further increased the proportion of highly dispersed copper. Additionally, molecular simulation techniques were employed to investigate the interaction between the reactants and the catalyst. Monte Carlo simulation showed that the adsorption capacity of zeolite for HCl was further enhanced by the addition of Sr. Molecular dynamics simulation showed that the addition of Sr reduced the diffusion of reactants in the catalyst support channel and promoted the catalytic reaction.

Electrocatalytic Anaerobic Oxidation of Benzylic Amines Enabled by Ferrocene-Based Redox Mediators.

The generation and functionalization of carbon- or nitrogen-centered radicals are of great interest for their potential synthetic utility. Here, we report the anaerobic electrocatalytic oxidation of two primary benzylic amines, benzylamine and 2-picolylamine, in the presence of a catalytic quantity of an electron deficient ferrocene derivative as a single-electron redox mediator. The use of the appropriate redox mediator prevented fouling of the electrode surface and significantly decreased the potential at which the catalytic oxidation reaction occurred. Simulation of the electrochemical results revealed an ErCi' catalytic process between the redox mediator and both substrates and significant difference in the electron transfer rate between the two substrates and electrochemically oxidized mediator. Through anaerobic controlled-potential electrolysis, we demonstrated a method with a Faradaic efficiency of 90% forming the desired coupled imine product of benzylamine oxidation while avoiding an excess of problematic overoxidation, hydrolysis, and other side reactions. Based on the electrochemical data along with the product analyses using IR and 1H and 13C NMR spectroscopies, the proposed mechanistic steps for the redox mediated electrocatalytic process were laid out.

Deep mineralization of bisphenol A via Cu–Mn spinel oxide nanospheres anchored N-doped carbon activated peroxymonosulfate

Fenton-like technology can efficiently remove recalcitrant pollutants, but developing catalytic oxidation system for deep mineralization of pollutants remains a challenge. Therefore, Cu–Mn spinel oxide nanospheres anchored N-doped carbon (CMO/NC) was prepared by a one-step calcination method and used to activate peroxymonosulfate (PMS) for efficient mineralization of bisphenol A (BPA). With the use of 0.5 g/L CMO/NC and 0.2 g/L PMS, the added BPA (50 mg/L) was completely degraded and deeply mineralized (nearly 95.2 %) in 9 min. The apparent first-order degradation rate constant k was 0.557 min−1, which was 61.9, 6.2 and 2.5 times than those in the systems of N-C/PMS (0.009 min−1), CuO/NC/PMS (0.09 min−1) and Mn3O4/NC/PMS (0.22 min−1). A comparison between the catalytic performances of CMO/NC catalysts prepared by changing the dosage of urea confirmed the catalysis synergism between Cu–Mn spinel oxides and N-C. A further comparison between the catalytic performances of CMO/NC catalysts prepared by varying the Cu/Mn molar ratio of the precursors showed that the synergy between Cu and Mn sites promoted the catalytic activity, with a synergistic effect factor of 1.8. XPS and H2-TPR characterizations proved that strong Cu-Mn interaction caused Mn species easier to donate electrons to PMS and Cu species easier to accept electrons from PMS. The degradation pathway and intermediate toxicity suggested that the system did not produce secondary pollution. Based on the results of EPR and capture experiments confirming that 1O2 was the major active species, a mechanism on PMS activation was proposed. Through investigations of continuous flow BPA wastewater removal, the influence of coexisting anions and catalyst cycling stability, it was clearly demonstrated that the present system had broad application prospects.

The promotional mechanism of Ce substituted A-site cation over YMn2O5 for toluene oxidation

Mullite-type YMn2O5 oxides have considerable potential for the removal of VOCs due to the abundance of lattice oxygen and the stability. The present study investigated the promotional mechanism of toluene oxidation by A-site cations of YMn2O5 with Ce. Y1-xCexMn2O5 was synthetized by sol-gel method and characterized with various techniques. The results revealed that samples doping with Ce could notably enhanced the toluene oxidation performance, and the toluene conversion of Y0.97Ce0.03Mn2O5 was 32% higher than that of YMn2O5 at 300 ℃. Detailed characterizations demonstrated that the modification of Ce produced an interface between YMn2O5 and YMnO3, the strong interactions at the interface improved the content of Mn3+ and oxygen vacancies, which promoted the toluene oxidation performance. Furthermore, the intermediate of toluene oxidation on Y0.97Ce0.03Mn2O5 was performed by in-situ DRIFTS. Toluene was sequentially oxidized to benzaldehyde, benzoic acid and maleic anhydride, ultimately produced H2O and CO2. This work offered a material science basis for the development of manganese-based mullite in thermal catalytic oxidation of toluene.

Electrochemical Conversion of Low-Cost Glycerol to Valuable Products

Over the last years, biodiesel production, a renewable fuel derived from biomass, has significantly increased, reaching an output of 40 million tons annually. This surge in production has resulted in excessive glycerol production, as a byproduct, accounting for 10 wt.% of biodiesel production. By 2025, it is predicted that glycerol production will amount to 6.3 million tons.1 However, the low demand for glycerol not only causes high disposal costs for this waste byproduct but also poses a threat to the ecosystem. Consequently, the valorization of glycerol is crucial for enhancing the biodiesel industry's economic viability and environmental sustainability.Among all the techniques for the valorization of glycerol, such as catalytic oxidation, dehydration, and hydrogenolysis, the electrochemical oxidation of glycerol stands out for its cost-effectiveness, simplicity, and eco-friendliness. The glycerol electrooxidation reaction (GOR) can yield a wide range of valuable chemicals, such as C3 products (glyceraldehyde, lactic acid, glyceric acid, tartronic acid), C2 products (glycolic acid, oxalic acid, acetic acid), and C1 products (formic acid). Among all the products, C3 products have notably higher economic value compared to others. In particular, glyceric acid stood out by having a price of over 200 folds of glycerol and having the highest worldwide demand among all the GOR products.2 However, a significant technical challenge lies in developing a highly selective catalyst for C3 products showing high activity, and stability. Thus far, most of the catalyst developed for GOR includes noble metals or their alloys, which limits their usage in realistic systems due to their high cost and scarcity.3 Therefore, developing a cost-effective catalyst with high selectivity, activity, and stability is necessary to make the valorization of glycerol economically viable.In this work, we demonstrate a bimetallic catalyst that, despite its low noble metal content, achieves high selectivity towards glyceric acid, along with notable catalytic activity and stability. Our analysis focuses on the impact of noble metal amount on activity and stability, and parametric analysis to improve the selectivity of C3 products. Furthermore, we outline the reasons for the discrepancies in the quantification of GOR products, especially in applying H-NMR analysis, and discuss the methods to improve the precision in GOR product analysis.

Customized Ultrathin Oxygen Vacancy-Rich Bi2W0.2Mo0.8O6 Nanosheets Enabling a Stepwise Charge Separation Relay and Exposure of Lewis Acid Sites toward Broad-Spectrum Photothermal Catalysis.

Designing robust photocatalysts with broad light absorption, effective charge separation, and sufficient reactive sites is critical for achieving efficient solar energy conversion. However, realizing these aims simultaneously through a single material modulation approach poses a challenge. Here, a 2D ultrathin oxygen vacancy (Ov)-rich Bi2W0.2Mo0.8O6 solid solution photocatalyst is designed and fabricated to tackle the dilemma through component and structure optimization. Specifically, the construction of a solid solution with ultrathin structure initially facilitates the separation of photoinduced electron-hole pairs, while the introduction of Ov strengthens such separation. In the meantime, the presence of Ov extends light absorption to the NIR region, triggering a photothermal effect that further enhances the charge separation and accelerates the redox reaction. As such, photoinduced charge carriers in the Ov-Bi2W0.2Mo0.8O6 are separated step by step via the synergistic action of 2D solid solution, OV, and solar heating. Furthermore, the introduction of OV exposes surface metal sites that serve as reactive Lewis acid sites, promoting the adsorption and activation of toluene. Consequently, the designed Ov-Bi2W0.2Mo0.8O6 reveals an enhanced photothermal catalytic toluene oxidation rate of 2445µmolg-1h-1 under a wide spectrum without extra heat input. The performance is 9.0 and 3.9 times that of Bi2WO6 and Bi2MoO6 nanosheets, respectively.

Kinetics of Oxygen Catalyst Based on Pyrochlore Oxide Nano-Particles for Low Temperature Water Electrolysis

Alkaline water electrolysis is carried out at 60 to 80 oC using nickel-based electrode materials and highly concentrated KOH solutions, which make highly corrosive environment against the electrodes, the separator, the current collector, and the others of the cell. Reduction in operating temperature would be preferable to suppress corrosion, although it would also make the catalytic activity for OER and HER down, making the cell voltage up. Since oxygen evolution is known as a high overpotential reaction which is more than 400 mV with nickel-based oxides at 60 oC or more, and alternative materials with lower overpotential and higher stability for OER in AWE have been needed. This paper presents a novel oxygen catalyst nano-particles based on bismuth ruthenium oxide, in which ruthenium at the B site in the pyrochlore structure is partly replaced with manganese1).Mn-doped bismuth ruthenium oxide (MBRO) was prepared by precipitation of metal hydroxide precursor, which had been obtained by addition of NaOH solution into the metal salt solution containing Bi(III) and Ru(III) with Mn(II), followed by calcination at 600 oC. XRD, EDX, EXAFS, ICP-AES, and RBS were used for structural and compositional analyses of MBRO. The obtained oxide was added into distilled water and the solution was treated by ultrasonic vibration to make a suspension, which was then dropped on a titanium disk (4 mm diam.) and dried at RT for 24 h, resulting in oxide particles-coated titanium disk, in which no binders or ionomers were used in the process. The disk was mounted in a commercial rotating disk electrode and was used as the working electrode with a platinum counter electrode, an Hg/HgO reference electrode, and 0.1 mol/L KOH solution. Polarization curves were measured by LSV for OER, of which the results were analyzed to obtain the onset potential, Tafel slope, exchange current density. All measurements were performed at RT (25 oC).EDX and EXAFS studies of MBRO showed that Ru(IV) was replaced with Mn(IV) at the B-site of pyrochlore structure, and this doping made a single phase of pyrochlore structure oxide without sub-product up to 30 at% replacement . Linear sweep voltammetry revealed the overpotential of MBRO for OER was less than 200 mV and the Tafel slope analysis of the LSV curve gave 40 mV/dec or less. The onset potential and the Tafel slope were almost the same when Ru:Mn atomic ratio of MBRO was changed from 100:0 to 70:30 at%. Further analysis of the polarization curve indicated the exchange current density slightly decreased with increasing Mn ratio. These results suggest that Ru is the active site for OER but Mn is as well. The Tafel slope of OER catalysts reported in literatures is mostly 60 mV/dec or more, including more than 200 mV/dec of nickel-based oxides2,3). Therefore, MBRO is a hyper catalytic oxide for OER in alkaline media and can significantly reduce the overpotential of the anode in AWE even at ambient temperature.Ref.1) M. Morimitsu, Patent US.2022085387.A1.2) T. Shinagawa, A. T. Garcia-Esparza, K. Takanabe, Scientific Reports, Vol. 5, Article No.13801 (2015).3) S. Yagi, et al., Nature Communications, Vol. 6, Article No. 8249 (2015).

Enzyme Engineering to Produce SWCNT Nanosensors as a Generalizable Platform for Biochemical Imaging and Sensing

Single-walled carbon nanotubes (SWCNT) stand out as attractive candidates for near-infrared (nIR) fluorescent imaging and chemical sensing. However, to render SWCNT chemically-selective, rational design of the surface corona is required to achieve sufficient sensitivity and selectivity to the target analyte. Recently, we reported on a facile sonication-based generation of glucose oxidase (GOx)-SWCNT conjugate for glucose detection [1]. Notably, we found that the analyte response mechanism does not involve catalytic oxidation of glucose, which motivated us to develop nanosensors using catalytically inactive GOx for enhanced reversibility and biocompatibility. In this study, we study the generalizability of our approach in producing SWCNT-based nanosensors based on 1- facile direct probe tip sonication, and 2- with engineered enzymes, showing the potential applicability of the sonication-based approach as a generalizable strategy for generating rationally designed nanosensors capable of detecting and imaging various analytically-relevant biomolecules.In this work, to test the generalizability of generating enzyme-SWCNT nanosensors, we generated conjugates by facile direct sonication of SWCNT with following enzymes: GOx, choline oxidase (ChOx), horseradish peroxidase (HRP), acetylcholineesterase, tyrosinase, cholesterol oxidase (CholOx), lactate oxidase, alcohol oxidase, xanthine oxidase, and galactose oxidase. Remarkably, six out of nine enzymes yielded stable suspensions of enzyme-SWCNT conjugates following probe-tip sonication, all of which successfully worked as nanosensors to detect their corresponding analytes. These nanosensors, in particular HRP-SWCNT and CholOx-SWCNT, exhibited excellent responses to their targets, with a maximum ΔF/F 0 of up to 300 % and 100 %, respectively. H2O2 is known to quench SWCNT fluorescence, and H2O2 nanosensors previously developed with SWCNT exhibited a negative fluorescence modulation as the sensor output with some challenges towards nanosensor selectivity. We highlight that our approach enables HRP-SWCNT nanosensor generation, which provides a strong ΔF/F 0 = 300 % and instantaneous turn-on response towards H2O2 within 2 s. Next, we sought to show that enzyme inactivation can produce SWCNT-based nanosensors that detect analytes without analyte consumption. To do so, we use ChOx as a model system to show that recombinant enzymes can be used as a generalizable approach to generating catalytically-inactive nanosensors. As expected, nanosensors prepared with mutant-ChOx exhibited responses comparable to those prepared with native ChOx, but without consuming the analyte or producing toxic byproducts such as H2O2. Thus, sonication-based physisorption of engineered enzymes to SWCNTs holds the potential to facilitate rapid nanosensor generation capable of detecting various biologically relevant molecules with reversibility and biocompatibility, thereby motivating their use in in vivo applications.[1] Nishitani, S., Tran, T., Puglise, A., Yang, S. & Landry, M. Engineered Glucose Oxidase-Carbon Nanotube Conjugates for Tissue-Translatable Glucose Nanosensors. Angew. Chem. Int. Ed Engl. e202311476 (2023)

Earth-Abundant Metal Oxides as Oxygen Evolution Electrocatalysts in 1 M H2SO4

Water splitting is a very hot research topic as a preferred source for green hydrogen, as a key vector to facilitate a transition into an environmentally friendly and sustainable energy economy in the mid-term. But it is still far from being economically competitive with respect to current hydrogen production technologies based on fossil fuels. One of the major economic hurdles to reduce electrolysis costs is the lack of low-cost catalysts for hydrogen evolution and, more importantly, for oxygen evolution. The water oxidation process is considered the main bottleneck in the advancement of water splitting devices, since it is the rate limiting process, and the main cause of poor long-term performance.Most recent advances in the field of water oxidation catalysis are based on transition metal oxides, operating exclusively in alkaline electrolysis conditions. Unfortunately, these excellent oxygen evolution catalysts in basic pH ( > 13) rapidly lose their activity when the pH is lowered, and are far away from the performance exhibited by noble metals in acid solution. McCrory et al. established in 2013 1a benchmarking protocol to identify the potential of new OER electrocatalysts (and extended in 2015 2 to HER) comparing the initial activity and stability of the materials as a function of pH and showed how no other known catalysts at that time came close to the performance of IrOx-based materials.A simple processing technique using a partially hydrophobic binder has been proved to stabilize Co oxide, resulting in electrodes able to reach high current densities (> 10 mA cm-2) at competitive overpotentials and with long term stability for acidic OER catalysis3. Following this strategy, we have been able to conduct an extensive survey of the activity and stability of monometallic, binary and ternary earth-abundant transition metal oxides during electrocatalytic OER in 1 M H2SO4. Our results confirm the general validity of the strategy in using a partially hydrophobic electrode to confer high stability to common metal oxides under these harsh conditions.[1] C.C.L. McCrory, S. Jung, J.C. Peters, T.F. Jaramillo, Benchmarking heterogeneous electrocatalysts for the oxygen evolution reaction, J. Am. Chem. Soc. 135 (2013) 16977–16987.[2] C.C.L. McCrory, S. Jung, I.M. Ferrer, S.M. Chatman, J.C. Peters, T.F. Jaramillo, Benchmarking Hydrogen Evolving Reaction and Oxygen Evolving Reaction Electrocatalysts for Solar Water Splitting Devices, J. Am. Chem. Soc. 137 (2015) 4347–4357.[3] J. Yu, F.A. Garcés-Pineda, J. González-Cobos, M. Peña-Díaz, C. Rogero, S. Giménez, M.C. Spadaro, J. Arbiol, S. Barja, J.R. Galán-Mascarós, Sustainable oxygen evolution electrocatalysis in aqueous 1 M H2SO4 with earth abundant nanostructured Co3O4, Nat. Commun. 13 (2022) 4341. Figure 1

Size and Electronic Effects on Redox Potentials and Electrocatalytic Processes Performed by Corrole-Chelated Metal Complexes

The future of our planet critically depends on the introduction of new or improved strategies for developing non-polluting energy production. Leading approaches are the electrocatalytic production of hydrogen gas, development of fuel cells relying on efficient reduction of oxygen and either gaseous or liquid fuels, as well as efficient reduction of carbon dioxide. Metal complexes chelated by N4 macrocycles serve as excellent catalysts in many of these processes, performed at both homogeneous and heterogeneous conditions. Our contributions to those aspect focused on introducing metallocorroles as catalysts for reduction of protons, oxygen and carbon dioxide, as well as for water oxidation [1-5]. The common motif in these and other publications was to take advantage of the relatively easy functionalization of the macrocyclic periphery for the tuning of properties and reactivity. A significant game changer was the recently reported synthetic access to corroles with meso-CF3 substituents and even to the parent corrole with no substituents whatsoever [6]. These developments allow for a focus on the size effect, which according to both hypothesis and fast accumulating results has a very strong effect (“smaller is better”) on the performance of electrodes modified by the corresponding metal complexes [7-9].References Sinha, N. Fridman, Y. Diskin-Posner, L. J. W. Shimon and Z. Gross “Superstructured Metallocorroles for Electrochemical CO2 Reduction”, Chem. Commun. 2019, 55, 11912-11915.Sinha, A. Mahammed, N. Fridman and Z. Gross “Water Oxidation Catalysis by Mono- and Binuclear Iron Corroles” ACS Catal. 2020, 10,3764-3772.Sudhakar, A. Mahammed, Q.-C. Chen, N. Fridman, B. Tumanskii and Z. Gross “Copper Complexes of CF3‐Substituted Corroles for Affecting Redox Potentials and Electrocatalysis” ACS Appl. Energy Mater. 2020, 3, 2828-2836.Yadav, I. Nigel-Etinger, A. Kumar, A. Mizrahi, A. Mahammed, N. Fridman, S. Lipstman,I. Goldberg, and Z. Gross “Hydrogen Evolution Catalysis, by Terminal Molybdenum-Oxo Complexes”, Iscience 2021, 24, 102924.-C. Chen, S. Fite, N. Fridman, B. Tumanskii, A. Mahammed, and Z. Gross “Hydrogen Evolution Catalyzed by Corrole-Chelated Nickel Complexes, Characterized in all Catalysis-relevant Oxidation States”, ACS Catalysis 2022, 12, 4310−4317.Kumar, P. Yadav, M. Majdoub, I. Saltsman, N. Fridman, S. Kumar, A. Kumar,A. Mahammed and Z. Gross “Corroles: The Hitherto Elusive Parent Macrocycle and its Metal Complexes” Angew. Chem. 2021, 60, 25097-25103. Mahammed and Z. Gross “Milestones and Most Recent Advances in Corrole’s Science and Technology”, J. Am. Chem. Soc. 2023, 145, 12429–12445Raslin, J. Douglin, A. Kumar, M. Fernandez-Dela-Mora, D. Dekel and Z. Gross “Size and electronic effects on the performance of (corrolato)cobalt-modified electrodes for ORR catalysis”. Inorg. Chem. 2023, 62, 14147–14151.Kumar, S. Fite, A. Raslin, S. Kumar, A. Mizrahi, A. Mahammed, and Z. Gross “Beneficial Effects on the Cobalt-Catalyzed Hydrogen Evolution Reaction Induced by Corrole Chelation”. ACS Catal. 2023, 13, 13344-13353. Figure 1

Highly efficient Cu(II) coordination polymer catalyst for the conversion of hazardous volatile organic compounds

Three novel coordination polymers (CPs), namely [Cu(μ-1κO,2κN-L)2]n (1), [Zn (μ-1κO,2κN-L)2(H2O)2]n (2) and [Cd (μ-1κOO’,2κN-L)2]n (3) [where HL = 4-(pyrimidin-5-ylcarbamoyl)benzoic acid], were synthesized and characterized by elemental analysis, ATR-IR, TGA, XPS and single-crystal X-ray diffraction. Despite having the same organic ligand, the various metal cations had an impact in the subsequent frameworks. Hirshfeld surface analysis was performed to investigate the intermolecular interactions and to examine the stability of the crystal structures of the three polymers. Their catalytic performances were screened for the peroxidative oxidation of Volatile Organic Compounds (VOCs), with toluene and p-xylene selected as model substrates. Tert-butyl hydroperoxide (t-BuOOH or TBHP) (aq. 70 %) was employed as the oxidant. The catalytic oxidation of toluene yielded benzyl alcohol, benzaldehyde and benzoic acid. The copper CP 1 exhibited the highest total yield for toluene oxidation, reaching approximately 36% in an aqueous medium. For p-xylene oxidation, tolualdehyde, methylbenzyl alcohol, and toluic acid were produced as the primary products, accompanied by minor ones. The experiments were conducted under diverse conditions, manipulating key parameters such as the choice of solvent (water or acetonitrile), type of oxidant (t-BuOOH or H2O2), the concentration of the oxidant and reaction temperature. In the presence of catalyst 1, a maximum total yield of ca. 80% was achieved for p-xylene oxidation.

Oxidative and Reductive Manipulation of C1 Resources by Bio-Inspired Molecular Catalysts to Produce Value-Added Chemicals.

ConspectusTo tackle the energy and environmental concerns the world faces, much attention is given to catalytic reactions converting methane (CH4) and carbon dioxide (CO2) as abundant C1 resources into value-added chemicals with high efficiency and selectivity. In the oxidative conversion of CH4 to methanol, it is necessary to solve the requirement of strong oxidants due to the large bond-dissociation energy (BDE) of the C-H bonds in methane and achieve suppression of overoxidation due to the smaller BDE of the C-H bond in methanol as the product. On the other hand, to efficiently perform CO2 reduction, proton-coupled electron transfer (PCET) processes are required since the reduction potential of CO2 becomes positive by using proton-coupled processes; however, under the acidic conditions required for PCET, hydrogen evolution by the reduction of protons becomes competitive with CO2 reduction. Thus, it is indispensable to develop efficient catalysts for selective CO2 reduction. Recently, we have developed efficient catalytic reactions toward the alleviation of the concerns mentioned above. Concerning CH4 oxidation, inspired by metalloenzymes that oxidize hydrophobic organic substrates, a hydrophobic second coordination sphere (SCS) was introduced to an FeII complex bearing a pentadentate N-heterocyclic carbene ligand, and the FeII complex was used as a catalyst for CH4 oxidation in aqueous media. Consequently, CH4 was efficiently and selectively oxidized to methanol with 83% selectivity and a turnover number of 500. In contrast, when methanol was used as a substrate for catalytic oxidation by the FeII complex, oxidation products were obtained in a negligible yield, which was comparable to that of the control experiment without the catalyst. Therefore, the hydrophobic SCS of the FeII complex can capture only hydrophobic substrates such as CH4 and release hydrophilic products such as methanol to the aqueous medium for suppressing overoxidation ("catch-and-release" mechanism). On the other hand, for photocatalytic CO2 reduction, we have developed NiII complexes with N2S2-chelating ligands as catalysts, which have been inspired by carbon monoxide dehydrogenase, and have also introduced a binding site of Lewis-acidic metal ions to the SCS of the Ni complex. When Mg2+ was applied as a moderate Lewis acid, a Mg2+-bound Ni catalyst allowed us to achieve remarkable enhancement of the photocatalytic CO2 reduction to afford CO as the product with over 99% selectivity and a quantum yield of 11.4%. Divalent metal ions besides Mg2+ also showed similar positive impacts on photocatalytic CO2 reduction, whereas monovalent metal ions exhibited almost no effects and trivalent metal ions exclusively promoted hydrogen evolution. In this Account, we highlight our recent progress in the catalytic manipulations of CH4 and CO2 as C1 resources.

Acid-activated α-MnO2 for photothermal co-catalytic oxidative degradation of propane: Activity and reaction mechanism

In order to further reduce the energy consumption of the conventional thermal catalytic oxidation system and improve the degradation efficiency of pollutants, photothermal synergistic catalytic oxidation (PTSCO) system was constructed in this paper with propane as simulated pollutant representing VOCs, and then the modified α-MnO2 catalysts were prepared by using the acid activation method, which were used for the catalytic oxidation of propane in PTSCO. The α-MnO2 with appropriate acid concentration possessed excellent low-temperature reducibility, abundant active oxygen species, fast oxygen migration rate and a large number of acid sites. The optimal catalyst, H0.05-MnO2, had a T90 of 204 °C in the PTSCO system, which reduced by more than 30 °C relative to the α-MnO2 (T90 of 235 °C). Moreover, H0.05-MnO2 demonstrated excellent water resistance and long-term stability (T = 45 h). It was shown that the combination of photocatalysis and thermocatalysis can improve propane degradation by examining the kinetics of propane degradation in the PTSCO system and the conformational relationship of propane degradation by catalysts. Furthermore, a multi-pathway synergistic mechanism between photocatalysis and thermocatalysis in the PTSCO system was proposed. This work provided a theoretical basis for the preparation of high-performance catalysts and the catalytic degradation of propane.

Homogeneous Tungsten Catalysis for Controllable Selective Oxidation of Anilines via the W(O)(η2-O2)2 Intermediate

Homogeneous Tungsten Catalysis for Controllable Selective Oxidation of Anilines via the W(O)(η²-O₂)₂ Intermediate

Preparation of LMO@FC catalysts and degradation of tetracycline by catalytic ozonation

Developing efficient catalysts with good stability holds great significance for better applying catalytic ozone oxidation in advanced wastewater treatment. Therefore, we designed a novel catalyst of LaMnO3-loaded foam ceramics (LMO@FCs) for catalytic ozonation of tetracycline hydrochloride (TCH) in water. The LaMnO3 (LMO) active components were uniformly loaded on the foam ceramics (FCs) to form an LMO@FC catalyst with mesoporous structure. The total organic carbon (TOC) removal rate by ozonation with LMO@FCs was 2.13 times that of ozone alone. After five repeated uses, the removal rate of TCH and TOC reached more than 99 % and 51.3 %, respectively. The conversion of ozone to reactive oxygen species (ROS) increased with the growth of initial pH. When pH reached zero point of charge (pHpzc), the ozone adsorption on the catalyst surface decreased, leading to the worst degradation efficiency. The Mn3+/Mn4+ and lattice oxygen (OL2−) and surface hydroxyl radical (·OH) were distributed on the catalyst surface. ·OH, superoxide anion (·O2−), and singlet oxygen (1O2) coexisted in the process of ozonation catalyzed by LMO@FCs. The surface ·OH of the catalyst was the catalytic active site. The electrostatic balance between Mn3+ and Mn4+ and the oxidation-reduction between O2− and O2 also played a crucial role in catalytic activity. The TCH experienced a series of reactions in the O3/LMO@FCs process, such as hydroxylation, demethylation, ring-opening oxidation and defunctionalization, and finally was mineralized into CO2, H2O, and NH4+. These results demonstrated that LMO@FCs are promising catalysts for catalytic ozonation of pharmaceutical wastewater treatment.

Kinetic Selectivity of an Electric Field-Induced Nonradical Pathway for Catalytic Oxidation of Phenolic Pollutants by Molecular Oxygen

Kinetic Selectivity of an Electric Field-Induced Nonradical Pathway for Catalytic Oxidation of Phenolic Pollutants by Molecular Oxygen

Carbonaceous structures as electronic bridges to enhance charge migration and radical reactions in composite photocatalysts: An effective way to achieve efficient mineralization of pollutants

The intrinsic correlation between photo-induced extraction of hole and free radical reactions can facilitate the mineralization of contaminants via promoting the transfer of electrons from the semiconductor to the solution. TiO2/C/g-C3N4 composite photocatalysts are prepared using thermal polycondensation and sol-gel methods in this paper. The introduction of carbon at the interface between the two phases creates charge migration channels that facilitate electron transfer at the interface of semiconductor catalyst as well as collisions of dissolved oxygen to the catalytic sites, which are able to promote catalytic oxidation reactions. Considering Rh-B as target, the removal rate is 97.2±0.2 % within 90 min. The involvement of hydroxyl radicals and superoxide radicals is confirmed by carrying out radical quenching experiments and ESR characterization, suggesting that effective electron transfer synergistically promotes the production of hydroxyl radicals. Therefore, it emphasizes the importance of the indeterminate carbon bridged 2D/3D interface for constructing charge migration channels as well as promoting the efficiency of carrier separation in the process of photocatalytic efficient degradation of dyes.