Ingenious construction of a magnetic-recyclable photo-Fenton catalyst ZnFe2O4@MIL-88A(Fe) and its adsorption-degradation activity toward levofloxacin

Monotonic pore size and particles inseparability of metal-organic frameworks (MOFs) caused serious effects on its light absorption ability and charge separation, restricting its application for antibiotic such as levofloxacin (LEV) degradation in water. In this study, a magnetically detachable nano-photocatalyst (ZnFe2O4@MIL-88A(Fe)) was synthesized using a simple two-step hydrothermal technique. The morphology and microstructure analyses showed that n-type ZnFe2O4 catalyst particles were efficiently assembled onto the surface of MIL-88A(Fe) crystal. Photocatalytic activity studies indicated that the ZnFe2O4@MIL-88A(Fe) plus H2O2 exhibiting a significantly boosted photo-Fenton activity toward LEV at visible light irradiation, compared to the pure ZnFe2O4 and MIL-88A(Fe), the degradation efficiency accordingly reached up to nearly 82% and 25% within 60 min. This excellent photocatalytic performance was ascribed to the synergistic effects of the heterogeneous structure of ZnFe2O4 and MIL-88A(Fe), whereby the efficient separation of charge carriers in the catalytic system is mutually reinforced with the efficient reduction of Fe3+ and Fe2+. Meanwhile, the degradation mechanism and intermediates of LEV during the photo-Fenton reaction process were also studied in depth through free radical burst, electron paramagnetic resonance, and mass spectrometry analyses, etc. Additionally, the ZnFe2O4@MIL-88A(Fe) composite catalyst displayed significant stability and ease of separation, indicating potential for the photo-oxidative degradation of organic pollutants.

Synthesis of a Co/Ni-MOF-74@PDI Z-scheme photocatalyst as a highly efficient photo-assisted Fenton-like catalyst for the removal of chlortetracycline hydrochloride

In this paper, ultra-thin nanofiber PDI was obtained by self-assembly dispersion of commercial PDINH. A novel Co/Ni-MOF-74@PDI Z-scheme heterojunction photocatalyst material was constructed by a simple solvothermal method. XRD, SEM, TEM, FT-IR and other characterization techniques proved the successful preparation of the Co/Ni-MOF-74@PDI Z-scheme heterojunction photocatalyst material. By degrading chlortetracycline hydrochloride, it was found that the photocatalytic activity of Co/Ni-MOF-74@PDI was much higher than that of pure Co/Ni-MOF-74 and PDI. Subsequently, Co/Ni-MOF-74@PDI was used to activate H2O2 to further improve the degradation efficiency of chlortetracycline hydrochloride. It was found that the photocatalytic performance was greatly improved after the addition of 19.6 mM H2O2 to the system, and the degradation rate of chlortetracycline hydrochloride was 87% within 90 min. The electron transfer pathway and H2O2 activation mechanism of the Co/Ni-MOF-74@PDI composite photocatalyst were proved by free radical quenching experiments, electron paramagnetic resonance analysis and X-ray electron spectroscopy. Finally, the easy exfoliation point and degradation pathway of chlortetracycline hydrochloride were studied using density functional theory, UPLC-MS and toxicity evaluation software. It was found that the main active substances were h+, ˙O2, 1O2 and ˙OH, and the toxicity of chlortetracycline hydrochloride and its intermediates was evaluated.

Synthesis of magnetic graphene-like carbon nitride-cobalt ferrite (g-C3N4/CoFe2O4) nanocomposite for sonocatalytic remediation of toxic organic dyes

A novel magnetic g-C₃N₄/CoFe₂O₄ nanocomposite was successfully synthesized by a simple hydrothermal method and applied as a new graphene-like carbon nitride-based sonocatalyst for sonodegradation of pollutant dyes. The as-prepared samples were characterized by using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS), BET surface area measurements and photoluminescence (PL) spectroscopy. The results indicate that the nanocomposite sample is composed of spherical CoFe₂O₄ nanoparticles adhered to g-C₃N₄ naosheets. The g-C₃N₄/CoFe₂O₄ nanocomposites were used as a new magnetically separable sonocatalyst in H₂O₂-assisted sonodegradation of methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) dyes in aqueous media. The results showed complete degradation (ca. 100%) of dyes within short times (30-35 min). The sonocatalytic activity of graphitic carbon nitride (g-C₃N₄) was greatly enhanced with CoFe₂O₄ modification. Trapping experiments indicated that the g-C₃N₄/CoFe₂O₄ nanocomposites serves as a generator of hydroxyl radical (˙OH) via activation of H₂O₂ for degradation of dyes under ultrasound irradiation. Furthermore, the magnetic sonocatalyst can be separated from solution by an external magnet and reused several times without observable loss of activity. The possible mechanism of sonocatalytic activity was also proposed according to experimental results.

Recent Advances in the Heterogeneous Photocatalytic Hydroxylation of Benzene to Phenol

Phenol is an important chemical material that is widely used in industry. Currently, phenol is dominantly produced by the well−known three−step cumene process, which suffers from severe drawbacks. Therefore, developing a green, sustainable, and economical strategy for the production of phenol directly from benzene is urgently needed. In recent years, the photocatalytic hydroxylation of benzene to phenol, which is economically feasible and could be performed under mild conditions, has attracted more attention, and development of highly efficient photocatalyst would be a key issue in this field. In this review, we systematically introduce the recent achievements of photocatalytic hydroxylation of benzene to phenol from 2015 to mid−2022, and various heterogeneous photocatalysts are comprehensively reviewed, including semiconductors, polyoxometalates (POMs), graphitic carbon nitride (g−C3N4), metal–organic frameworks (MOFs), carbon materials, and some other types of photocatalysts. Much effort is focused on the physical and chemical approaches for modification of these photocatalysts. The challenges and future promising directions for further enhancing the catalytic performances in photocatalytic hydroxylation of benzene are discussed in the end.

Graphitic carbon nitride: a sustainable photocatalyst for organic pollutant degradation and antibacterial applications

Recently, graphitic carbon nitride (GCN) has been found to be of great interest in various sustainable applications. In this study, a simple preparation method using urea was utilized to synthesize GCN. In order to understand various morphological, structural, and optical aspects of the as-prepared sample, GCN was characterized using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, Brunauere-Emmette-Teller (BET), scanning electron microscopy (SEM), and diffused reflectance spectra (DRS) analysis. The visible-light-driven photocatalytic activity of prepared GCN was analyzed for various cationic dyes (Crystal violet, rose bengal, rhodamine B, auramine O, methylene blue) and anionic dyes (phenol red, xylenol orange, cresol red, methyl orange). The calculated efficiencies of degradation and values of apparent rate constant for all dye samples suggested that cationic dyes are more actively degraded using GCN than anionic dyes. In addition, GCN was further analyzed for its splendid antibacterial activity against pathogenic bacteria (Klebsiella pneumonia and Escherichia coli). The synthesized photocatalyst holds a bright scope for the efficient remediation of organic pollutants and bacterial disinfection in wastewater. Graphical abstract.

Bifunctional reusable Co0.5Ni0.5Fe2O4 nanoparticle-grafted carbon nanotubes for aqueous dye removal from contaminated water

Highly stable and reusable CNF-grafted CNTs for efficient and effective aqueous dye removal from contaminated waters.

Synergetic Effect of Facet Junction and Specific Facet Activation of ZnFe2O4 Nanoparticles on Photocatalytic Activity Improvement

Crystal facet engineering has been proved as a versatile approach in modulating the photocatalytic activity of semiconductors. However, the facet-dependent properties and underlying mechanisms of spinel ZnFe₂O₄ in photocatalysis still have rarely been explored. Herein, ZnFe₂O₄ nanoparticles with different {001} and {111} facets exposed were successfully synthesized via a facile hydrothermal method. Facet-dependent photocatalytic degradation performance toward gaseous toluene under visible light irradiation was observed, where truncated octahedral ZnFe₂O₄ (ZFO(T)) nanoparticles with both {001} and {111} facets exposed exhibited a superior performance than the others. The formed surface facet junction between {010} and {100} facets was responsible for the improved activity by separating photogenerated e^-/h⁺ pairs efficiently to reduce their recombination rate. Photogenerated electrons and holes were demonstrated to be immigrated onto {001} and {111} facets, separately. Intriguingly, electron paramagnetic resonance trapping results indicated that both ^•O₂^- and ^•OH were abundantly present in the ZFO(T) sample under visible light irradiation as major reactive oxygen species involved in the photocatalytic degradation process. Additionally, further investigation revealed that {001} facets played a predominant role in activating photogenerated transient species H₂O₂ into ^•OH, beneficially boosting the intrinsic photocatalytic activity. This work has not only presented a promising strategy in regulating photocatalytic performance through the synergetic effect of facet junction and specific facet activation but also broadened the application of facet engineering with multiple effects simultaneously cooperating.

Recyclable magnetic NiFe2O4/C yolk–shell nanospheres with excellent visible-light-Fenton degradation performance of tetracycline hydrochloride

A NiFe₂O₄/C yolk–shell nanostructure was prepared via one-step calcination using polyacrylic acid sodium salt (PAAS) NPs as a template, which exhibited a highly efficient visible-light photocatalytic performance for the removal of TC in the presence of H₂O₂.

The construction of a Fenton system to achieve in situ H2O2 generation and decomposition for enhanced photocatalytic performance

A photo-Fenton system combining Ni_xFe_yO₄–BiOBr with the in situ generation and decomposition of H₂O₂ was constructed for efficient organic compound degradation.

Properties of magnetic carbon nanomaterials and application in removal organic dyes

Magnetic carbon nanomaterials were prepared facilely by one step hydrothermal synthesis method using biologically regenerated glucose as carbon sources and ferric ammonium citrate as iron sources. As-synthesized nanomaterials were characterized by means of SEM, TEM, XRD, N₂ adsorption-desorption, VSM and XPS etc. techniques. Results show as-prepared magnetic nanomaterials are sphere particles with aggregation state and magnetic α-Fe particles are enclosed by carbon matrixes. With increase of calcination temperature, the degrees of the sample aggregation decrease, whereas the average particle sizes, BET specific surface areas and saturation magnetizations increase. The carbon with graphite structure has higher adsorption efficiency than that of amorphous carbon for organic dye rhodamine B in water. Whereas the iron with amorphous structure shows higher photocatalytic activity than that of the iron with crystalline structure for the degradation of rhodamine B. And rhodamine B in water can almost be degraded completely through the combination of adsorption and photocatalysis.

Highly improved visible-light-induced photocatalytic performance over BiOI/Ag2CO3 heterojunctions

The heterojunctions between BiOI and Ag₂CO₃ obviously improved visible-light-driven photocatalytic activity compared with separate BiOI and Ag₂CO₃ particles.

Construction of flower-like MoS2/Fe3O4/rGO composite with enhanced photo-Fenton like catalyst performance

Flower-like MoS₂/Fe₃O₄/rGO composites have been constructed, which exhibit highly efficient visible-light photocatalytic performance for removing of RhB in the presence of H₂O₂.

1,3-Disulfoimidazolium chloronickellate immobilized HZSM-5 framework as visible-light-induced heterogeneous photocatalyst for advanced oxidation process

Hybrid photocatalysts of [Dsim]₂[NiCl₄]/HZSM-5 were prepared by wet impregnation and their application is demonstrated as feasible heterogeneous photocatalysts for oxidative degradation of methylene blue under sunlight.

Synthesis and photoelectrocatalytic activity of In2O3 hollow microspheres via a bio-template route using yeast templates

In₂O₃ hollow microspheres synthesized using yeast as a bio-template with the aid of a precipitation method have demonstrated higher photoelectrocatalytic activity in degrading methylene blue (MB).