An Efficient Anthraquinone-Resin Hybrid Co-Catalyst for Fenton-Like Reactions: Acceleration of the Iron Cycle Using a Quinone Cycle under Visible-Light Irradiation

Self-assembled Cupric Oxide Nanoclusters for Highly efficient chemodynamic therapy

Chemodynamic therapy (CDT) based on Fenton and Fenton-like reactions induces cancer cell killing via in situ catalyzing H₂ O₂ and generating highly oxidative hydroxyl radicals (⋅OH) in tumor sites. Their application is not limited by tumor grown depth or hypoxic microenvironment. However, the reaction efficiency is still hampered due to the structure of catalytic agents and the requirement for low pH environment. Here, we design a porous CuO nanocluster (CuO NC) through self-assembly of oleylamine stabilized CuO NPs (OAm-CuO NPs), and functionalize it with folic acid (CuO NC-FA) for specific tumor cell targeting. It can catalyze H₂ O₂ with high efficiency in nearly neutral environment. Besides, the porous structure of CuO NC also helps the diffusion of H₂ O₂ to the interior of nanocluster to further improve Fenton-like reaction efficiency. The convenient synthesis of CuO NC-FA with good Fenton-like reaction efficiency at neutral environment demonstrates good chemodynamic therapy effect.

Integration of homogeneous and heterogeneous advanced oxidation processes: Confined iron dancing with cyclodextrin polymer

A novel catalyst which integrates heterogeneous and homogenous Fenton reactions is designed and fabricated by encapsulating 2,5-dihydroxy-1,4-benzoquinone (2,5-DBQ) in ECDP-Fe₃O₄, a composite of Fe₃O₄ nanoparticles immobilized on a β-cyclodextrin polymer (ECDP) with ethylene diamine tetraacetic acid (EDTA) as cross-linking agent. The 2,5-DBQ@ECDP-Fe₃O₄ has superior catalytic performance for 4-nitrophenol and 2,4-dichlorophenol degradation compared with control systems. Mechanism study revealed that although the initial active site is Fe₃O₄ loaded on ECDP, the actually catalyst is the iron ions released from Fe₃O₄ but confined within the composite. EDTA in β-cyclodextrin polymer can improve both the solubility and adsorption capacity to H₂O₂ of Fe₃O₄. The quinone molecules 2,5-DBQ in the β-cyclodextrin cavity can accelerate Fe³⁺/Fe²⁺ cycle adjacent to the cavity, thus in favor of the decomposition of H₂O₂ into OH as main reactive oxidizing species. The current catalyst integrates the advantages of homogeneous and heterogeneous advanced oxidation processes and is promising in practical applications.

Enhanced Generation of Reactive Oxygen Species under Visible Light Irradiation by Adjusting the Exposed Facet of FeWO4 Nanosheets To Activate Oxalic Acid for Organic Pollutant Removal and Cr(VI) Reduction

In this work, taking FeWO₄ nanosheets as an example, the activation of oxalic acid (OA) based on facet engineering for the enhanced generation of active radical species was reported, revealing unprecedented surface Fenton activity for pollutant degradation. Density functional theory calculations confirmed the more efficient generation of reactive oxygen species over FeWO₄ nanosheets with the {001} facet exposed (FWO-001) under visible light irradiation compared to the efficiency of FeWO₄ nanosheets with the {010} facet exposed (FWO-010), which could be attributed to a higher density of iron and the efficient activation of OA on the {001} facet. The H₂O₂-derived ^•OH tended to diffuse away from the active sites of FWO-001 into solution to favor the continuous activation of OA into the active radicals for pollutant redox reactions, but preferred to remain on FWO-010 to hinder the further activation of OA on the {010} facet. Additionally, the generation of ^•CO₂^- endowed FeWO₄ with a strong reduction ability. Compared with FWO-010, FWO-001 exhibited enhanced redox activity for the catalytic degradation of organic pollutants and Cr(VI) in the optimized conditions. These findings can help in understanding the facet dependent surface Fenton chemistry of catalytic redox reactions and in designing efficient catalysts for environmental decontamination.

Singlet Oxygen Triggered by Superoxide Radicals in a Molybdenum Cocatalytic Fenton Reaction with Enhanced REDOX Activity in the Environment

As an important reactive oxygen species (ROS) with selective oxidation, singlet oxygen (¹O₂) has wide application prospects in biology and the environment. However, the mechanism of ¹O₂ formation, especially the conversion of superoxide radicals (·O₂^-) to ¹O₂, has been a great controversy. This process is often disturbed by hydroxyl radicals (·OH). Here, we develop a molybdenum cocatalytic Fenton system, which can realize the transformation from ·O₂^- to ¹O₂ on the premise of minimizing ·OH. The Mo⁰ exposed on the surface of molybdenum powder can significantly improve the Fe³⁺/Fe²⁺ cycling efficiency and weaken the production of ·OH, leading to the generation of ·O₂^-. Meanwhile, the exposed Mo⁶⁺ can realize the transformation of ·O₂^- to ¹O₂. The molybdenum cocatalytic effect makes the conventional Fenton reaction have high oxidation activity for the remediation of organic pollutants and prompts the inactivation of Staphylococcus aureus, as well as the adsorption and reduction of heavy metal ions (Cu²⁺, Ni²⁺, and Cr⁶⁺). Compared with iron powder, molybdenum powder is more likely to promote the conversion from Fe³⁺ to Fe²⁺ during the Fenton reaction, resulting in a higher Fe²⁺/Fe³⁺ ratio and better activity regarding the remediation of organics. Our findings clarify the transformation mechanism from ·O₂^- to ¹O₂ during the Fenton-like reaction and provide a promising REDOX Fenton-like system for water treatment.

Quinone-modified metal-organic frameworks MIL-101(Fe) as heterogeneous catalysts of persulfate activation for degradation of aqueous organic pollutants

In this work, quinone-modified metal-organic framework MIL-101(Fe)(Q-MIL-101(Fe)), as a novel heterogeneous Fenton-like catalyst, was synthesized for the activation of persulfate (PS) to remove bisphenol A (BPA). The synthetic Q-MIL-101(Fe) was characterized via X-ray diffraction, scanning electron microscope, Fourier transform infrared, electrochemical impedance spectroscopy, cyclic voltammetry and X-ray photoelectron spectroscopy. As compared to the pure MIL-101(Fe), Q-MIL-101(Fe) displayed better catalytic activity and reusability. The results manifested that the Q-MIL-101(Fe) kept quinone units, which successfully promoted the redox cycling of Fe³⁺/Fe²⁺ and enhanced the removal efficiency. In addition, the reaction factors of Q-MIL-101(Fe) were studied (e.g. pH, catalyst dosage, PS concentration and temperature), showing that the optimum conditions were [catalyst] = 0.2 g/L, [BPA] = 60 mg/L, [PS] = 4 mmol/L, pH = 6.79, temperature = 25 °C. On the basis of these findings, the probable mechanism on the heterogeneous activation of PS by Q-MIL-101(Fe) was proposed.

Preparation of reduced graphene oxide nanosheet/FexOy/nitrogen-doped carbon layer aerogel as photo-Fenton catalyst with enhanced degradation activity and reusability

In this manuscript, a novel reduced graphene oxide nanosheet/Fe_xO_y/nitrogen-doped carbon layer (rGS/Fe_xO_y/NCL) aerogel with Fe_xO_y NPs sandwiched between rGS and NCL was prepared via a two-step method. Their catalytic performance was evaluated in a photo-Fenton degradation of rhodamine B. It was found that rGS/Fe_xO_y/NCL aerogel represented higher degradation activity than the sum of rGS/NCL support and Fe_xO_y NPs, suggesting synergistic effect was established between support and reactive species. The degradation activity was investigated on the basis of aerogel usage, Fe_xO_y loading, H₂O₂ dosage, pH value and RhB concentration. To test stability and reusability, leaching experiments, cyclic experiments and structural analysis were carried out. Based on inhibitor experiment and intermediate detection, a possible catalytic mechanism and degradation pathway of RhB were proposed.

Strongly enhanced Fenton degradation of organic pollutants by cysteine: An aliphatic amino acid accelerator outweighs hydroquinone analogues

Quinone-hydroquinone analogues have been proven to be efficient promoters of Fenton reactions by accelerating the Fe(III)/Fe(II) redox cycle along with self-destruction. However, so far there is little information on non-quinone-hydroquinone cocatalyst for Fenton reactions. This study found that cysteine, a common aliphatic amino acid, can strongly enhance Fenton degradation of organic pollutants by accelerating Fe(III)/Fe(II) redox cycle, as quinone-hydroquinone analogues do. Further, cysteine is superior to quinone-hydroquinone analogues in catalytic activity, H₂O₂ utilization and atmospheric limits. The cocatalysis mechanism based on the cycle of cysteine/cystine was proposed.

Bio-inspired double-layer structure artificial microreactor with highly efficient light harvesting for photocatalysts

The artificial TiO₂leaves microreactors replicated from submerged aquatic needle-like leaves with double-layer structure showed superior light harvesting capability and photocatalytic performance.