Defects materials of Institut Lavoisier-125(Ti) materials enhanced photocatalytic activity for toluene and chlorobenzene mixtures degradation: Mechanism study

In situ growth of bismuth oxybromide/bismuth molybdate 2D/2D Z-scheme heterojunctions with rich interfacial oxygen vacancies for photocatalytic benzylic C(sp3)-H bond activation

The selective oxidation of toluene into valuable chemicals via photocatalytic C(sp3)-H bond activation represents a significant, yet challenging process. Here, the in situ construction of bismuth oxybromide/bismuth molybdate (BiOBr/Bi2MoO6) 2D/2D Z-scheme heterojunctions featuring interface-induced oxygen vacancies (OVs) is introduced. The optimized BiOBr/Bi2MoO6 sample has a remarkable yield rate of benzaldehyde at 2134.28 μmol g-1 h-1 under blue LED irradiation, surpassing the performance of BiOBr and Bi2MoO6 by 8.1 and 2.9 times, respectively. Insights from density functional theory (DFT) calculations, electron paramagnetic resonance (EPR), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies highlight the critical role of the Z-scheme electronic configuration and OVs in attaining the superior photocatalytic toluene conversion efficiency. This study advances the photocatalytic conversion of benzaldehyde within an OV-enhanced direct Z-scheme system, facilitating the activation of inert C(sp3)-H bonds, and contributes to the development of high-performance catalysts for sustainable chemical processes.

Insight into the Synergistic Effect of Binary Nonmetallic Codoped Co3O4 Catalysts for Efficient Ethyl Acetate Degradation under Humid Conditions

The synthesis of high-performance catalysts for volatile organic compounds (VOCs) degradation under humid conditions is essential for their practical industrial application. Herein, a codoping strategy was adopted to synthesize the N-Co3O4-C catalyst with N, C codoping for low-temperature ethyl acetate (EA) degradation under humid conditions. Results showed that N-Co3O4-C exhibited great catalytic activity (T 90 = 177 °C) and water resistance (5.0 vol% H2O, T 90 = 178 °C) for EA degradation. Characterization results suggested that the C, N codoping weakened the Co-O bond strength, increased surface Co3+ and Oads species, and improved the low-temperature redox ability and the mobility of lattice oxygen species, which boosted the catalytic performance of N-Co3O4-C for EA degradation. Meanwhile, the N-doping-induced oxygen vacancies could interact with water vapor to generate extra active oxygen species, which enhanced the water resistance. Importantly, based on a series of characterization technologies, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and theoretical calculations, the synergistic effect of C, N codoping was systematically investigated and elucidated. The C doping induced the increase of surface area and the weakening of Co-O bond strength, which improved EA adsorption and lattice oxygen species activation to dissociate and oxidize EA, forming the key intermediate, acetate acid. N doping enhanced the adsorption and activation of gaseous oxygen species to form active oxygen species, attacking and breaking the C-C bond in acetate acid to accelerate EA deep oxidation, which synergistically facilitated EA degradation.

Fabrication of Z-Scheme MIL-125/Ag/BiOBr Heterojunctions with Enhanced Photocatalytic Reduction of Cr6

Herein, first, MIL-125 samples were synthesized via a hydrothermal method. Then, Ag species were doping on the surface of MIL-125 samples via the photolysis of silver nitrate. Finally, the Z-scheme MIL-125/Ag/BiOBr composite was synthesized via a directed liquid assembly method. The structure, morphology, and optical properties of the prepared samples were investigated via X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopic mapping, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, N2 adsorption-desorption analysis, ultraviolet-visible spectroscopy, photoluminescence spectroscopy, surface photovoltage analysis, transient photocurrent response analysis, electrochemical impedance spectroscopy, and electron spin resonance analysis. Photocatalytic experiments indicated that the photocatalytic Cr6+ reduction efficiency of MIL-125/Ag/BiOBr heterojunctions was 85.7% at pH = 6, which was approximately 5.5 and 2.2 times higher than that using BiOBr and MIL-125 alone, respectively. This performance was attributed to the intimate interfacial contact between MIL-125 and BiOBr and the doping of Ag species, which increased the transfer and separation of photogenerated carriers and inhibited the recombination of electrons and holes. Furthermore, the possible photocatalytic Cr6+ reduction mechanism of the Z-scheme MIL-125/Ag/BiOBr photocatalyst was proposed.

Tuning the metal-support interactions in titanium dioxide-supported palladium photocatalysts against toluene in air

The activity of supported noble metal (e.g., palladium (Pd)) catalysts is often governed by the combined effects of multiple factors (e.g., electronic and geometric properties of the support, surface chemistry of metal nanoparticles (NPs), and metal-support interactions). Pd/titanium dioxide (TiO2) catalyst has been developed as a highly efficient photocatalytic degradation (PCD) system against gaseous toluene based on high-temperature pretreatment (300 and 450 °C) in a mixed stream of hydrogen (H2) and (N2). The interaction of Pd NPs with TiO2 synergistically improves the PCD efficiency of toluene through the efficient adsorption and activation of toluene as well as molecular oxygen (O2) and water (H2O) for the facile generation of reactive oxygen species (ROS (e.g., superoxide anion (•O2-) and hydroxyl (•OH) radicals)). The PCD efficiency of the prepared sample against 5 ppm toluene (at 20% relative humidity (RH)) is 79.6% with the values of maximum reaction rate, quantum yield, space-time yield, and clean air delivery rate as 9.9 μmol g-1 h-1, 1.68E-03 molecules photon-1, 1.68E-02 molecules photon-1 g-1, and 4.8 L h-1, respectively. Based on this research, the PCD mechanism of gaseous toluene has been explored along with the dynamic behavior of O2 and H2O for ROS generation and their relative contribution to the PCD of toluene. As such, this research offers a perspective for designing advanced photocatalysts through surface defect engineering.

Efficient VOCs photodegradation through local ion substitution in TiO2-C composites derived from MIL-125(Ti)

Volatile organic compounds (VOCs) are the main cause of environmental pollution and numerous respiratory diseases. Most VOCs molecules can be entirely converted into H2O and CO2 by photocatalytic technology without the demand for additional oxidants, making it an ideal choice for air purification. However, for conventional photocatalysts, a smaller specific surface area is not conducive to enriching VOCs molecules on the surface of catalyst. To address this, a functionalized porous C-TiO2 composite was synthesized by a self-sacrificing template method. The resulting porous carbon layer can serve as an adsorption medium to enrich VOCs molecules, while the photocatalytic reaction occurs on the TiO2 surface. On the basis of the experimental results, the remarkable properties of the catalysts can be attributed to the doping of carbon atoms into oxygen vacancies (OVs) and the formation of Ti@C bonds. Additionally, the study confirmed that C-TiO2 possesses abundant surface defects and Ti-OH groups, which can facilitate the rapid generation of •OH groups on the catalyst surface, thus aiding in the catalytic oxidation process of VOCs molecules.

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 2445 µmol g-1 h-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.

MIL-88-NH2(Fe) conjugated pectin through a post-modification Ugi four-component reaction: A robust bio-based catalyst for the synthesis of cyclic carbonate via CO2 fixation reaction

The functionalization of materials via multicomponent reactions (MCRs) led to a recent surge in the interest of researchers, owing to the creation of exceptional properties in materials. Herein, a novel robust porous catalyst was prepared via the conjugation of MIL-88-NH2(Fe) and pectin (DAP/MIL-88-NH2(Fe)) through the post-modification Ugi four-component reaction (Ugi-4CR) for the first time. To achieve this aim, pectin was oxidized using sodium periodate as an oxidant agent to produce dialdehyde pectin (DAP). Next, the generated carbonyl functional groups participated in the Ugi-4CR of MIL-88-NH2(Fe), 4-methyl carboxylic acid, and cyclohexyl (c-hex) isocyanide to produce DAP/MIL-88-NH2(Fe) catalyst. The catalytic activity of the prepared bio-based catalyst was examined in producing cyclic carbonates through the chemical fixation of CO2 with epoxides in the presence of TBAB as a co-catalyst. Interestingly, catalytic experiments revealed that the prepared bio-based catalyst could be remarkably active regarding the CO2 fixation reaction and performed it in the shortest reaction time (1 h) via high CO2 adsorbent capacity. The outstanding benefits of the prepared bio-based catalyst include its non-hazardous nature, inexpensive, green and gentle reaction conditions, and ability to be reusable in several runs with slight loss of catalytic activity due to a more durable framework with high chemical and thermal stability.

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.

Crystal-Defect-Induced Longer Lifetime of Excited States in a Metal-Organic Framework Photocatalyst to Enhance Visible-Light-Mediated CO2 Reduction

We report the structural defects in Zr-metal-organic framework (MOFs) for achieving highly efficient CO2 reduction under visible light irradiation. A series of defective Zr-MOF-X (X = 160, 240, 320, or 400) are synthesized by acid-regulated defect engineering. Compared to pristine defect-free Zr-MOF (NNU-28), N2 uptake increases for Zr-MOF-X synthesized with the HAc modulator, producing a larger pore space and Brunauer-Emmett-Teller surface area. The pore size distribution demonstrates that defective Zr-MOF-X exhibits mesoporous structures. Electrochemistry tests show that defective Zr-MOF-X possesses a more negative reduction potential and a higher photocurrent responsive signal than that of pristine NNU-28. Consequently, the defective samples exhibit a significantly higher efficiency in the photoreduction of CO2 to formate. Transient absorption spectroscopies manifest that structural defects modulate the excited-state behivior of Zr-MOF-X and improve the photogenerated charge separation of Zr-MOF-X. Furthermore, electron paramagnetic resonance and in-suit X-ray photoelectron spectroscopy provide additional evidence of the high photocatalytic performance exhibited by defective Zr-MOF-X. Results demonstrate that structural defects in Zr-MOF-X also improve the charge transfer, producing abundant Zr(III) catalytically active sites, exhibiting a slower decay process than defect-free Zr-MOF. The long-lifetime Zr(III) species in defective Zr-MOF-X are fully exposed to a high-concentration CO2 atmosphere, thereby enhancing the photocatalytic efficiency of CO2 reduction.

Mesoporous cobalt-manganese layered double hydroxides promote the activation of calcium sulfite for degradation and detoxification of metronidazole

Metronidazole (MNZ), a commonly used antibiotic, poses risks to water bodies and human health due to its potential carcinogenic, mutagenic, and genotoxic effects. In this study, mesoporous cobalt-manganese layered double hydroxides (CoxMny-LDH) with abundant oxygen vacancies (Ov) were successfully synthesized using the co-precipitation method and used to activate calcium sulfite (CaSO3) with slight soluble in water for MNZ degradation. The characterization results revealed that Co2Mn-LDH had higher specific areas and exhibited good crystallinity. Co2Mn-LDH/CaSO3 exhibited the best catalytic performance under optimal conditions, achieving a remarkable MNZ degradation efficiency of up to 98.1 % in only 8 min. Quenching experiments and electron paramagnetic resonance (EPR) tests showed that SO4•- and 1O2 played pivotal roles in the MNZ degradation process by activated CaSO3, while the redox cycles of Co2+/Co3+ and Mn3+/Mn4+ on the catalyst surface accelerated electron transfer, promoting radical generation. Three MNZ degradation routes were put forward based on the density functional theory (DFT) and liquid chromatography-mass spectrometer (LC-MS) analysis. Meanwhile, the toxicity analysis result demonstrated that the toxicity of intermediates post-catalytic reaction was decreased. Furthermore, the Co2Mn-LDH/CaSO3 system displayed excellent stability, reusability, and anti-interference capability, and achieved a comparably high removal efficiency across various organic pollutant water bodies. This study provides valuable insights into the development and optimization of effective heterogeneous catalysts for treating antibiotic-contaminated wastewater.

Mechanistic study of visible light driven photocatalytic degradation of clofibric acid using Fe-based metal organic frameworks (MOFs)

Although a series of past studies proved the potential usage of Fe-based metal-organic frameworks (MOFs) as photocatalysts, there remains a knowledge gap of the photocatalytic mechanism stemming from the challenge to separate the simultaneous sorption and photocatalytic degradation. Thus, this article aimed to suggest a novel approach by desorbing target molecules during photocatalysis to excavate the underlying mechanisms of sorption and photocatalytic degradation. In this study, two Fe-based MOFs, MIL-101(Fe) and MIL-101(Fe)-NH2, were selected to remove clofibric acid under visible light irradiation. Prior to photocatalysis, sorption mechanism was uncovered based on the sorption kinetic, isotherm, thermodynamic interpretation, and of its dependence on solution pH. The results inferred that the primary sorption mechanism was through the π-π interaction between the benzene ring of clofibric acid and the organic ligand of Fe-based MOFs. Based on these results, photocatalytic mechanism could be independently or jointly assessed during the photocatalytic degradation of clofibric acid. Subsequently, the application of the Tauc method and XPS spectra revealed that the bandgap structure of Fe-based MOFs had the potential to oxidize clofibric acid by producing ROS through the electron excitation upon visible-light illumination. On top of that, the amine functionalization of Fe-based MOF altered the structural moiety that led to an additional strong acid-base interaction with clofibric acid but a decrease in the bandgap limiting the ROS production during photocatalytic activity.

Fluorination modification enhanced the water resistance of Universitetet i Oslo-67 for multiple volatile organic compounds adsorption under high humidity conditions: Mechanism study

The construction of metal-organic frameworks (MOFs) with highly efficient capture for volatile organic compounds (VOCs) adsorption under humid conditions is a significant yet formidable task. Herein, series of fluorinated UiO-67 modified with trifluoroacetic acid (TFA) and 4-fluorobenzoic acid were successfully synthesized for VOCs adsorption under high humidity conditions. Experiments results showed that UiO-67 modified with 4-fluorobenzoic acid (67-F) presented excellent adsorption capacity of 345 mg/g for toluene adsorption and exhibited great water resistance (10.0 vol% H2O, 374 mg/g toluene adsorption capacity). Characterization results indicated that the introduction of 4-fluorobenzoic acid induced the competitive coordination between 4-fluorobenzoic acid and 4,4-biphenyl dicarboxylic acid (BPDC) with Zr4+, causing the formation of abundant defects to provide extra adsorption sites. Meanwhile, the benzene ring in 4-fluorobenzoic acid enhanced the π-π conjugation, causing the further promotion of VOCs adsorption capacity. More importantly, the water resistance mechanism was investigated and elucidated that the introduction of F decreased the surface energy of 67-F and its affinity with water. Meanwhile, the metal complex induced by the fluorinated modification produced an electron-dense pore environment, which greatly improved its chemical and water stability. This work provided a strategy for preparing an adsorbent with high water resistance for real-world VOCs adsorption at high humidity conditions.

Derivatives of Br-doped metal-organic framework for improved acetaldehyde adsorption-photocatalytic oxidation

Different Br-doped metal-organic frameworks (MOFs) derived (Brx@UiO-66) have been prepared by heat treatment using UiO-66 as the precursor. The experimental results showed that Br0.2@UiO-66 exhibited the best photocatalytic oxidation and adsorption performances toward acetaldehyde. In the dynamic system, the acetaldehyde removal rate and adsorption capacity of Br0.2@UiO-66 were 93.2 % and 230.59 mg/g, respectively. The improvement of the photocatalytic performance can be attributed to the presence of Br ions and CBr bonds, which facilitated the rapid separation of electrons and holes and the production of •O2-. In addition, Br0.2@UiO-66 had a better adsorption performance than 300UiO-66, mainly because of the increased Lewis acidity of the metal active sites due to Br doping. Radical capture experiments indicated that •O2- and e- were the primary active substances in acetaldehyde oxidation, and allowed establishing the possible mechanism of acetaldehyde oxidation. This work shows that MOFs can have high catalytic oxidation performances toward volatile organic compounds (VOCs) while retaining their adsorption capacity, and can be used for practical applications in the adsorption-catalytic integrated degradation of VOCs.

Magnetic FNS/MILs nanofibers for highly efficient removal of norfloxacin via adsorption and Fenton-like reaction

Iron-containing MOFs have attracted extensive interest as promising Fenton-like catalysts. In this work, magnetic Fe3O4 nanofiber (FNS)/MOFs composites with stable structure, included FNS/MIL-88B, FNS/MIL-88A and FNS/MIL-100, were prepared via the in-situ solvothermal method. The surface of the obtained fibers was covered by a dense and continuous MOFs layer, which could effectively solve the agglomeration problem of MOFs powder and improved the catalytic performance. The adsorption and catalytic properties of FNS/MOFs composites were evaluated by removal of norfloxacin. FNS/MIL-88B showed the best performance with a maximum adsorption capacity up to 214.09 mg/g, and could degrade 99% of NRF in 60 min. Meanwhile, FNS/MIL-88B had a saturation magnetization of 20 emu/g, and could be rapidly separated by an applied magnetic field. The self-supported nanofibers allowed the adequate contact between MOFs and pollutants, and promoted the catalytic activity and high stability. We believe that this work provided a new idea for the design and preparation of Fenton-like catalysts especially MOFs composites.

Sulfur-containing iron carbon nanocomposites activate persulfate for combined chemical oxidation and microbial remediation of petroleum-polluted soil

In this study, sulfur-containing iron carbon nanocomposites (S@Fe-CN) were synthesized by calcining iron-loaded biomass and utilized to activate persulfate (PS) for the combined chemical oxidation and microbial remediation of petroleum-polluted soil. The highest removal efficiency of total petroleum hydrocarbons (TPHs) was achieved at 0.2% of activator, 1% of PS and 1:1 soil-water ratio. The EPR and quenching experiments demonstrated that the degradation of TPHs was caused by the combination of 1O2,·OH, SO4·-, and O2·-. In the S@Fe-CN activated PS (S@Fe-CN/PS) system, the degradation of TPHs underwent two phases: chemical oxidation (days 0 to 3) and microbial degradation (days 3 to 28), with kinetic constants consistent with the pseudo-first-order kinetics of chemical and microbial remediation, respectively. In the S@Fe-CN/PS system, soil enzyme activities decreased and then increased, indicating that microbial activities were restored after chemical oxidation under the protection of the activators. The microbial community analysis showed that the S@Fe-CN/PS group affected the abundance and structure of microorganisms, with the relative abundance of TPH-degrading bacteria increased after 28 days. Moreover, S@Fe-CN/PS enhanced the microbial interactions and mitigated microbial competition, thereby improving the ability of indigenous microorganisms to degrade TPHs.

S-scheme towards interfacial charge transfer between POMs and MOFs for efficient visible-light photocatalytic Cr (VI) reduction

The establishment of heterojunctions was considered as an exceptional strategy to obtain high-efficiency charge separation and enhanced photocatalytic performance. Herein, a series of FePMo/MIL-53(Fe) (FeM-53) heterojunctions were successfully constructed through in-situ growth of FePMo onto MIL-53(Fe) surface and their photocatalytic capacity were examined by visible-light-induced Cr(VI) reduction. Interestingly, the as-fabricated composites offered various photocatalytic activities controllably relying on the mass ratio of FePMo to MIL-53(Fe). Particularly, the one with the 10% ratio displayed the highest Cr(VI) reduction rate (100%) within 75 min, which was respectively over 4 and 2 folds higher than pure FePMo and MIL-53(Fe). The boosted photoactivity might be ascribed to the establishment of S-scheme heterojunction with suitable band alignment between FePMo and MIL-53(Fe), which broadened the light absorption range and improved charge separation. Further mechanism investigations implied both •O2- and e- were the key reactive species for Cr(VI) removal. Besides, the composite preserved excellent stability after 4 consecutive tests, and performed well in the presence of organic dyes. Such a S-scheme heterojunction may promise for highly efficient environmental mitigation.