Boosting catalytic degradation efficiency by incorporation of MIL-53(Fe) with Ti3C2Tx nanosheeets

Enhanced ozonation of vanillin catalyzed by highly efficient magnetic MnFe2O4/ZIF-67 catalysts: Synergistic effects and mechanism insights

In this study, we synthesized magnetic MnFe2O4/ZIF-67 composite catalysts using a straightforward method, yielding catalysts that exhibited outstanding performance in catalyzing the ozonation of vanillin. This exceptional catalytic efficiency arose from the synergistic interplay between MnFe2O4 and ZIF-67. Comprehensive characterization via x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FE-SEM), and energy dispersive spectroscopy (EDS) confirmed that the incorporation of MnFe2O4 promoted the creation of oxygen vacancies, resulting in an increased presence of l adsorbed oxygen (Oads) and the generation of additional ·OH groups on the catalyst surface. Utilizing ZIF-67 as the carrier markedly enhanced the specific surface area of the catalyst, augmenting the exposure of active sites, thus improving the degradation efficiency and reducing the energy consumption. The effects of different experimental parameters (catalyst type, initial vanillin concentration, ozone dosage, initial pH value, and catalyst dosage) were also investigated, and the optimal experimental parameters (300 mg/L1.0-MnFe2O4/ZIF-67, vanillin concentration = 250 mg/L, O3 concentration = 12 mg/min, pH = 7) were obtained. The vanillin removal efficiency of MnFe2O4/ZIF-67 was increased from 74.95% to 99.54% after 30 min of reaction, and the magnetic separation of MnFe2O4/ZIF-67 was easy to be recycled and stable, and the vanillin removal efficiency of MnFe2O4/ZIF-67 was only decreased by about 8.92% after 5 cycles. Additionally, we delved into the synergistic effects and catalytic mechanism of the catalysts through kinetic fitting, reactive oxygen quenching experiments, and electron transfer analysis. This multifaceted approach provides a comprehensive understanding of the enhanced ozonation process catalyzed by MnFe2O4/ZIF-67 composite catalysts, shedding light on their potential applications in advanced oxidation processes. PRACTITIONER POINTS: A stable and recyclable magnetic composite MnFe2O4/ZIF-67 catalyst was synthesized through a simple method. The synergistic effect and catalytic mechanism of the MnFe2O4/ZIF-67 catalyst were comprehensively analyzed and discussed. A kinetic model for the catalytic ozone oxidation of vanillin was introduced, providing valuable insights into the reaction dynamics.

Visible light enhanced persulfate activation for degradation of tetracycline via boosting adsorption of persulfate by ligand-deficient MIL-101(Fe) icosahedron

In this work, Fe-based metal-organic frameworks (Fe-MOFs) are prepared by a simple solvothermal method, in which acetic acid/N, N-dimethylformamide (HAc/DMF) mixture solvents are employed to regulate the particle morphology, exposed facets and ligand defects. At HAc/DMF = 0/50, 5/45 and 8/42 (volume ratio), the irregular particles (MIL-53(Fe)), elongated icosahedrons (5H-MIL-101(Fe)) and icosahedrons (8H-MIL-101(Fe)) are obtained, respectively. Under visible light irradiation (λ > 420 nm) and the addition of sodium persulfate (PS), 5H-MIL-101(Fe) shows the highest degradation activity for tetracycline (TC). Specifically, 80% of TC has been removed by 5H-MIL-101(Fe) within 25 min, and the degradation kinetics rate is 3.03 times higher than that over MIL-53(Fe). The improvement of catalytic activity is mainly attributed to the active facets exposed and ligand defects of 5H-MIL-101(Fe). Density functional theory (DFT) calculation further confirms that the active facets exposed and ligand defects of 5H-MIL-101(Fe) favor the adsorption and activation of PS, benefiting the generation of •SO₄^-. Besides, a probable degradation pathway of TC is proposed based on trapping experiments and liquid chromatography-mass spectrometry (LC-MS) test. Furthermore, the toxicities of intermediates are predicted by the quantitative structure-activity relationship (QSAR) mathematical model. This work demonstrates that visible light enhanced PS activation (Vis-PSA) can more effectively degrade organic pollutants, and this work also provides a simple strategy to precisely regulate ligand defects and actively exposed facets of Fe-MOFs to enhance the adsorption and activation of PS.

Rational design of ZnO-zeolite imidazole hybrid nanoparticles with reduced charge recombination for enhanced photocatalysis

Semiconducting zinc oxide nanoparticles (ZnO NPs) hold great potential as photocatalysts in wastewater treatment because of their favorable bandgap and cost-effectiveness. Unfortunately, ZnO NPs usually show rapid charge recombination that limits their photocatalytic efficacy significantly. Herein, we report a facile way of modifying ZnO NPs with zeolite imidazole framework-8 (ZIF8). A synergy between the two components may tackle the drawback of fast charge recombination for pristine ZnO NPs. Improved performance of photocatalytic degradation of methylene blue (MB) is confirmed by comparing with pristine ZnO and ZIF8 as the catalysts. The ZIF8 in the composite serves as a trap for photogenerated electrons, thus reducing the rate of charge recombination to enhance the photocatalysis rate. In addition, the hybridization process suppresses the aggregation of ZnO NPs, providing a large surface area and a greater number of active sites. Moreover, a small shift in the absorption band of ZnO@ZIF8 (10) NPs towards higher wavelength, also witnessed a little contribution towards enhanced photocatalytic properties. Mechanistic studies of the photocatalytic process of MB using ZnO@ZIF8 NPs catalyst reveal that hydroxyl radicals are the major reactive oxygen species. The facile hybridization of ZnO with ZIF8 provides a strategy for developing new photocatalysts with wide application potential.

Vertically grown CeO2 and TiO2 nanoparticles over the MIL53Fe MOF as proper band alignments for efficient H2 generation and 2,4-DCP degradation

The design of highly efficient photoca talysts for clean energy production and environmental remediation are the grand challenges of scientific research. Herein, TiO₂@MIL53Fe and CeO₂@MIL53Fe composite photocatalysts are synthesized via solvothermal technique. The SEM and TEM micrographs reveal that TiO₂ and CeO₂ nanoparticles are vertically grown onto the surface of MIL53Fe MOF. Further, HRTEM micrograph confirmed the formation of heterojunction. It has been investigated that the resultant TiO₂@MIL53Fe and CeO₂@MIL53Fe photocatalysts exhibit remarkably improved visible light activities for H₂ production and 2,4-dichlorophenol (2,4-DCP) degradation in comparison to the bare MIL53Fe photocatalyst. The enhanced photoactivities of the fabricated TiO₂@MIL53Fe and CeO₂@MIL53Fe photocatalysts are attributed to significantly promoted charge separation as confirmed via the surface photo voltage (SPV) and photoluminescence (PL) results. Further, the photocatalysts exhibit high stability and reusability as confirmed via the recyclable tests. This work will promote the design of MOF-based efficient photocatalysts for clean energy production and environment purification.

Degradation of tetracycline by FeNi-LDH/Ti3C2 photo-Fenton system in water: From performance to mechanism

Recently, photo-Fenton technology has been widely used to degrade tetracycline (TC) because of its great efficiency and wide application range. Herein, Fe-Ni layered double hydroxides (FeNi-LDH)/Ti₃C₂ photo-Fenton system was constructed in this study. The results showed the introduction of Ti₃C₂ solved some problems of FeNi-LDH such as poor conductivity, easy aggregation, and high recombination rate of photoelectron. Benefiting from these advantages, FeNi-LDH/Ti₃C₂ exhibited excellent TC removal rate of 94.7% while pure FeNi-LDH was only 54%. Besides, FeNi-LDH/Ti₃C₂ possessed strong pH tolerance (2-11) and the removal efficiency was still up to 82% after the four-cycle experiment. Furthermore, the quenching experiments revealed the reaction mechanism, where ∙OH and ·O₂^- were the primary active radicals for degrading TC. Last, the results of the simulated wastewater treatment and the inorganic ion interference tests showed that FeNi-LDH/Ti₃C₂ possessed practical application potential. In brief, this study shows that FeNi-LDH/Ti₃C₂ can offer a certain theoretical basis for the actual development of hydrotalcite in heterogeneous photo-Fenton systems.

Emerging architecture titanium carbide (Ti3C2Tx) MXene based photocatalyst toward degradation of hazardous pollutants: Recent progress and perspectives

MXenes family has aroused marvelous consideration as a frontier photoactive candidate for solar energy transformation and environmental remediation. 2D Ti₃C₂ exhibit a unique layered microstructure, large surface functional groups (-F, -OH, -O), substantial sorption selectivity, superior reduction efficiency, and electrical conductivity. Electronically conductive Ti₃C₂T_x with tunable energy band gap (0.92-1.75eV) makes it one of the most potential photoactive materials for photodegradation. The present review paper aims to design cost-effective heterojunctions and Schottky junctions of Ti₃C₂ with transition metal oxides, sulfides, g-C₃N₄, and other organic frameworks. The discussion mainly involves different aspects related to its tunable electronic structure, stability problems, and surface morphology control. In addition, the advantages of Ti₃C₂ in fabricating highly efficient Ti₃C₂ based catalytic junctions exhibiting suppressed charge carrier recombination are discussed with particular emphasis on their adsorption and redox properties for the removal of toxic dyes, heavy metal ions, and various pharmaceuticals. Finally, current challenges and research directions are outlined and prospected for the future development of Ti₃C₂ based photocatalytic systems.

Iron Carbon Catalyst Initiated the Generation of Active Free Radicals without Oxidants for Decontamination of Methylene Blue from Waters

In conventional oxidation technologies for treatment of contaminated waters, secondary pollution of the aqueous environment often occurs because of the additional oxidants generated during the process. To avoid this problem, Fe/NG catalyst composites without additives were developed in this study for decontamination of methylene blue (MB) from waters. The Fe/NG catalyst, composed of carbon nitride and iron chloride (FeCl3·6H2O), was prepared by high temperature pyrolysis. It is an exceptionally efficient, recoverable, and sustainable catalyst for degradation of organic matter. The morphological characteristics, chemical structure, and surface properties of the catalyst composites were investigated. The catalyst exhibited high MB removal efficiency (100%) within 30 min under ambient temperature and dark conditions. The experiments indicated that an MB degradation effect was also applicable under most acid–base conditions (pH = 2–10). The characterization results using electron spin resonance and analysis of intermediate products demonstrated that free radicals such as ·OH and ·O2− were produced from the Fe/NG composites in the heterogeneous system, which resulted in the high MB degradation efficiency. Moreover, the catalysis reaction generated reducing substances, triggering iron carbon micro-electrolysis to spontaneously develop a microcurrent, which assisted the degradation of MB. This study demonstrates the feasibility of Fe/NG catalysts that spontaneously generate active species for degrading pollutants in an aqueous environment at normal temperature, providing an attractive approach for treating organic-contaminated waters.

Boron nitride nanosheets decorated MIL-53(Fe) for efficient synergistic ibuprofen photocatalytic degradation by persulfate activation

In this study, based on one-step hydrothermal method, boron nitride nanosheets (BNNs) and MIL-53(Fe) composites (BNFe-X) were successfully prepared and the catalytic performance of BNFe-X on persulfate (PS) activation for ibuprofen (IBP) photodegradation was investigated. The introduction of BNNs changed the morphology of MIL-53(Fe) to be a unique prism-like structure and enhanced the degradation efficiency of IBP, which followed the pseudo-first-order rate kinetics. Among the prepared composites, BNFe-3 (3% BNNs) exhibited the highest IBP degradation activity and possessed strong stability after four cycles. Over 99% IBP removal was achieved at the irradiation time of 60 min. The promoted decomposition rate of IBP could be ascribed to be the activation of PS and the enhanced electrons transfer efficiency between BNNs and MIL-53(Fe). The scavenger studies and electron spin-resonance spectroscopy (ESR) demonstrated the generation of SO₂^-, OH and O₂^-, and all these radicals had the different contributions in IBP degradation. Based on the LC-MS-MS and TOC results, the possible decomposition pathways of IBP in BNFe-3/PS system were proposed. This work suggested that the BNNs/Fe-based MOFs composites and PS system had great potential in organic pollutants degradation in aqueous solution.

In2S3/BiOI composites boost visible-light photocatalytic degradation of tetracycline hydrochloride

In₂S₃/BiOI composites have potential to degrade tetracycline hydrochloride under visible light due to the synergistic effect between In₂S₃ and BiOI.

Biomass-based 0D/3D N-CQD/MIL-53(Fe) photocatalyst for the simultaneous remediation of multiple hazardous pollutants in sewage

The implementation of N-CQD/MIL-53(Fe) photocatalyst in the area of photocatalytic multi-component sewage remediation.

Electrochemically-deposited PANI on iron mesh-based metal-organic framework with enhanced visible-light response towards elimination of thiamphenicol and E. coli

Metal-organic frameworks (MOFs) are emerging class of porous materials that attracted tremendous attention as eco-friendly photocatalysts. However, poor charge separation in most MOFs largely thwarts their photocatalytic performance. In this work, Materials of Institut Lavoisier-100(Fe) (MIL-100 (Fe)) based on iron mesh was successfully fabricated by in situ growth. MIL-100(Fe) doped with polyaniline, namely MIL-100(Fe)/PANI, were then fabricated by galvanostatic deposition followed by annealing. Compared to pure MIL-100(Fe), MIL-100(Fe)/PANI composites exhibited excellent photocatalytic performances towards Thiamphenicol (TAP) degradation and Escherichia coli (E. Coli.) inactivation. The apparent rate constant, k, for TAP elimination of the MIL-100(Fe)/PANI composites with H₂O₂ is approximately 3 times as high as that of pure MIL-100(Fe). The electrochemical studies showed enhanced photocatalytic performances, which can be attributed to the electronic conductivity of PANI polymers. Quenching experiments, fluorescent tests and electron paramagnetic resonance (EPR) all suggested ⋅O₂^-, e^-, ⋅OH and h⁺ as reactive oxidizing species (ROSs) involved in the photocatalytic process, where ⋅OH played the predominant ROSs. The transformation products of TAP were also isolated and characterized by high-resolution mass spectrometry, and transformation pathways of TAP under Vis/MIL-100(Fe)/PANI/H₂O₂ were tentatively clarified based on involved intermediates. Herein, MOFs conjugated conductive polymers nanocomposites look promising as efficient photocatalysts for organic pollutants degradation and bacteria inactivation. This work could offer novel strategies for the development of heterojunction composites with enhanced photocatalytic performances for better environmental remediation.

In Situ Generation of Prussian Blue by MIL-53 (Fe) for Point-of-Care Testing of Butyrylcholinesterase Activity Using a Portable High-Throughput Photothermal Device

Butyrylcholinesterase (BuChE), the primary source of serum cholinesterase activity, is an indispensable biochemical marker for clinical diagnosis of liver function and organophosphorus poisoning. The requirement for bulky and expensive instruments represents a huge hindrance for point-of-care testing (POCT) of BuChE, especially in resource-limited settings. Herein, an easy-operated, economic, and portable photothermal (PT) biosensing platform for high-throughput BuChE detection was rationally designed. BuChE could "light up" the PT signal through in situ generation of Prussian blue (PB) by MIL-53 (Fe), which allowed us to translate biological signals into temperature signals. Such temperature change signals could be monitored at high throughput (six samples for a single measurement) by a miniature self-made integrated PT device via combining separable 96-well plates, a three-dimensional (3D) printed sample bracket, 808 nm lasers, and thermometers, satisfying the requirement for rapid on-site detection in a large batch with low cost. In addition, the large specific surface area, 3D network structure, and high porosity of MIL-53 (Fe) offered a beneficial platform for its reaction with enzymatic hydrolysate, resulting in high sensing sensitivity and low detection limit (0.3 U L^-1), which was at least 20 000 times lower than the normal human serum BuChE activity. This facile, affordable, and broad applicability PT sensing platform provides a beneficial reference for the rational design of other disease diagnostic approaches suitable for POCT.