Accelerating the Fe(III)/Fe(II) cycle via enhanced electronic effect in NH2-MIL-88B(Fe)/TPB-DMTP-COF composite for boosting photo-Fenton degradation of sulfamerazine

COF/In2S3 S-Scheme Photocatalyst with Enhanced Light Absorption and H2O2-Production Activity and fs-TA Investigation

Photocatalytic hydrogen peroxide (H2O2) synthesis from water and O2 is an economical, eco-friendly, and sustainable route for H2O2 production. However, single-component photocatalysts are subjected to limited light-harvesting range, fast carrier recombination, and weak redox power. To promote photogenerated carrier separation and enhance redox abilities, an organic/inorganic S-scheme photocatalyst is fabricated by in situ growing In2S3 nanosheets on a covalent organic framwork (COF) substrate for efficient H2O2 production in pure water. Interestingly, compared to unitary COF and In2S3, the COF/In2S3 S-scheme photocatalysts exhibit significantly larger light-harvesting range and stronger visible-light absorption. Partial density of state calculation, X-ray photoelectron spectroscopy, and femtosecond transient absorption spectroscopy reveal that the coordination between In2S3 and COF induces the formation of mid-gap hybrid energy levels, leading to smaller energy gaps and broadened absorption. Combining electron spin resonance spectroscopy, radical-trapping experiments, and isotope labeling experiments, three pathways for H2O2 formation are identified. Benefited from expanded light-absorption range, enhanced carrier separation, strong redox power, and multichannel H2O2 formation, the optimal composite shows an impressive H2O2-production rate of 5713.2 µmol g-1 h-1 in pure water. This work exemplifies an effective strategy to ameliorate COF-based photocatalysts by building S-scheme heterojunctions and provides molecular-level insights into their impact on energy level modulation.

The Application of Metal-Organic Frameworks in Water Treatment and Their Large-Scale Preparation: A Review

Over the last few decades, there has been a growing discourse surrounding environmental and health issues stemming from drinking water and the discharge of effluents into the environment. The rapid advancement of various sewage treatment methodologies has prompted a thorough exploration of promising materials to capitalize on their benefits. Metal-organic frameworks (MOFs), as porous materials, have garnered considerable attention from researchers in recent years. These materials boast exceptional properties: unparalleled porosity, expansive specific surface areas, unique electronic characteristics including semi-conductivity, and a versatile affinity for organic molecules. These attributes have fueled a spike in research activity. This paper reviews the current MOF-based wastewater removal technologies, including separation, catalysis, and related pollutant monitoring methods, and briefly introduces the basic mechanism of some methods. The scale production problems faced by MOF in water treatment applications are evaluated, and two pioneering methods for MOF mass production are highlighted. In closing, we propose targeted recommendations and future perspectives to navigate the challenges of MOF implementation in water purification, enhancing the efficiency of material synthesis for environmental stewardship.

Ligand-Induced Synthesis of Highly Stable NM88(DB)@COF-JLU19 Composite: Accelerating Electron Flow for Visible-Light-Efficient Degradation of Tetracycline Hydrochloride

In recent years, the response of new porous materials to visible light and their potential applications in wastewater treatment has received extensive attention from the scientific community. Metal Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs) have been the focus of attention due to their strong visible light absorption, high specific surface area, well-regulated pore structures, and diverse topologies. In this study, a novel MOF@COF composite with a high surface area, high crystallinity, and structural stability was obtained using the covalent bond formation strategy from COF-JLU19 and NH2-MIL-88B(Fe). Under visible light irradiation, the degradation of tetracycline hydrochloride by this material reached more than 90% within 10 min and was completely degraded within 30 min, which exceeded the degradation rate of individual materials. Remarkably, the catalytic activity decreased by less than 5% even after five degradation cycles, indicating good structural stability. The excellent photocatalytic performance of the NM88(DB)@COF-JLU19 hybrids was attributed to the formation of covalent bonds, which formed a non-homogeneous interface that facilitated effective charge separation and promoted the generation of hydroxyl radicals.

Hybrid organic frameworks: Synthesis strategies and applications in photocatalytic wastewater treatment - A review

Hybrid organic framework materials are a class of hierarchical porous crystalline materials that have emerged in recent years, composed of three types of porous crystal materials, namely metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and hydrogen-bonded organic frameworks (HOFs). The combination of various organic framework properties in hybrid organic frameworks generates synergistic effects, which has attracted widespread attention from researchers. The synthesis methods of hybrid organic frameworks are also an intriguing topic, enabling the formation of core-shell heterostructures through epitaxial growth, template conversion, medium growth, or direct combination. These hybrid organic framework materials have demonstrated remarkable performance in the application of photocatalytic wastewater purification and have developed various forms of applications. This article reviews the preparation principles and methods of various hybrid organic frameworks and provides a detailed overview of the research progress of photocatalytic water purification hybrid organic frameworks. Finally, the challenges and development prospects of hybrid organic framework synthesis and their application in water purification are briefly discussed.

Optimizing the performance of Fe-based metal-organic frameworks in photo-Fenton processes: Mechanisms, strategies and prospects

Contaminants in water pose a significant challenge as they are harmful and difficult to treat using conventional methods. Therefore, various new methods have been proposed to degrade organic pollutants in water, among which the photo-Fenton process is considered promising. In recent years, Fe-based metal-organic frameworks (Fe-MOFs) have gained attention and found applications in different fields due to their cost-effectiveness, non-toxic nature, and unique porous structure. Many researchers have applied Fe-MOFs to the photo-Fenton process in recent years and achieved good results. This review focuses on describing different strategies for enhancing the performance of Fe-MOFs in the photo-Fenton process. Also, the mechanism of MOF in the photo-Fenton process is described in detail. Finally, prospects for the application of Fe-MOFs in photo-Fenton systems for the treatment of organic pollutants in water are presented. This study provides information and ideas for researchers to use Fe-MOFs to remove organic pollutants from water by photo-Fenton process.

Simple ultrasonic integration of shapeable, rebuildable, and multifunctional MIL-53(Fe)@cellulose composite for remediation of aqueous contaminants

Metal-organic frames (MOFs) have been recognized as one of the best candidates in the remediation of aqueous contaminants, while the fragile powder shape restricts the practical implementation. In this work, a shapeable, rebuildable, and multifunctional MOF composite (MIL-53@CF) was prepared from MIL-53 (Fe) and cellulose fiber (CF) using a simple ultrasonic method for adsorption and photocatalytic degradation of organic pollutants in wastewater. The results showed MIL-53(Fe) crystals were uniformly growth on CF surfaces and bonded with surface nanofibrils of CF through physical crosslinking and hydrogen bonding. Because of the high bonding strength, the MIL-53@CF composite exhibited an excellent compressive strength (3.53 MPa). More importantly, the MIL-53@CF composite was rebuildable through mechanical destruction followed by re-ultrasonication, suggesting the excellent reusability of MIL-53@CF for water remediation. The MIL-53@CF composite also had high adsorption capacities for methyl orange (884.6 mg·g-1), methylene blue (198.3 mg·g-1), and tetracycline (106.4 mg·g-1). MIL-53@CF composite could degrade TC through photocatalysis. The photocatalytic degradation mechanism was attributed to the Fe(II)/Fe(III) transform cycle reaction of MIL-53 crystal located on MIL-53@CF. Furthermore, the mechanical property and remoldability of MIL-53@CF composite increased its practicability. Comprehensively, MIL-53@CF composite provided a possible strategy to practically apply MOF in the remediation of aqueous contaminants.

Fe-Cu bimetal metal-organic framework for efficient decontamination via Fenton-like process: Synthesis, performance and mechanism

Constructing Fe-Cu bimetal catalysts is an efficient strategy to promote Fe(III)/Fe(II) cycle, whereas there is still a long way to go before fully understanding the role of the Cu in the catalysts. Herein, a new Fe-MOF namely BUC-96(Fe) was fabricated from FeSO₄·7H₂O, 4,4'-bipyridine (bpy) and 2,5-dihydroxyterephthalic acid (H₄dhtp) by both hydrothermal reaction and microwave-assisted method. Also, bimetal BUC-96(FeCu-x) were obtained when the CuSO₄ was added into the system identical to the synthesis process of BUC-96(Fe). Series BUC-96 MOFs showed good organics elimination performance via Fenton-like process, where 88.1% (k = 0.0672 min^-1) of chloroquine phosphate (CQ, 20 mg/L) was decomposed over pristine BUC-96(Fe) within 30 min. Interestingly, nearly 100% CQ was degraded over BUC-96(FeCu-5) as catalyst under the identical conditions within 5 min, whose reaction rate (1.3527 min^-1) was 20.1-fold higher than that of BUC-96. Additionally, BUC-96(FeCu-5) exhibited excellent Fenton-like oxidation degradation performance for 10 selected emerging organic pollutants. The reaction mechanism was studied in detail by experiments, and density functional theory (DFT) calculation. The results revealed that the introduced Cu not only accelerated Fe(III)/Fe(II) cycles, hydroxyl radical (·OH) generation, electron transfer, but also lowered H₂O₂ dissociated energy barrier. This work advanced the bimetal MOFs construction and application in wastewater treatment via Fenton-like process.

Swellable Array Strategy Based on Designed Flexible Double Hypercross-linked Polymers for Synergistic Adsorption of Toluene and Formaldehyde

High-capacity adsorption and removal of complex volatile organic compounds (VOCs) from real-world environments is a tough challenge for researchers. Herein, a swellable array adsorption strategy was proposed to realize the synergistic adsorption of toluene and formaldehyde on the flexible double hypercross-linked polymers (FD-HCPs). FD-HCPs exhibited multiple adsorption sites awarded by a hydrophobic benzene ring/pyrrole ring and a hydrophilic hydroxyl structural unit. The array benzene ring, hydroxyl, and pyrrole N sites in FD-HCPs effectively captured toluene and formaldehyde molecules through π-π conjugation and electrostatic interaction and weakened their mutual competitive adsorption. Interestingly, the strong binding force of toluene molecules to the skeleton deformed the pore structure of FD-HCPs and generated new adsorption microenvironments for the other adsorbate. This behavior significantly improved the adsorption capacity of FD-HCPs for toluene and formaldehyde by 20% under multiple VOCs. Moreover, the pyrrole group in FD-HCPs greatly hindered H₂O molecule diffusion in the pore, thus efficiently weakening the competitive adsorption of H₂O toward VOCs. These fascinating properties enabled FD-HCPs to achieve synergistic adsorption for multicomponent VOC vapor under a highly humid environment and overcame single-species VOC adsorption properties on state-of-the-art porous adsorbents. This work provides the practical feasibility of synergistic adsorption to remove complex VOCs in real-world environments.

Visible-light-driven iron-based heterogeneous photo-Fenton catalysts for wastewater decontamination: A review of recent advances

Visible-light-driven heterogeneous photo-Fenton process has emerged as the most promising Fenton-derived technology for wastewater decontamination, owing to its prominent superiorities including the potential utilization of clean energy (solar light), and acceleration of ≡Fe(II)/≡Fe(III) dynamic cycle. As the core constituent, catalysts play a pivotal role in the photocatalytic activation of H₂O₂ to yield reactive oxidative species (ROS). To date, all types of iron-based heterogeneous photo-Fenton catalysts (Fe-HPFCs) have been extensively reported by the scientific community, and exhibited satisfactory catalytic performance towards pollutants decomposition, sometimes even exceeding the homogeneous counterparts (Fe(II)/H₂O₂). However, the relevant reviews on Fe-HPFCs, especially from the viewpoint of catalyst-self design are extremely limited. Therefore, this state-of-the-art review focuses on the available Fe-HPFCs in literatures, and gives their classification based on their self-characteristics and modification strategies for the first time. Two classes of representative Fe-HPFCs, conventional inorganic semiconductors of Fe-containing minerals and newly emerging Fe-based metal-organic frameworks (Fe-MOFs) are comprehensively summarized. Moreover, three universal strategies including (i) transition metal (TMs) doping, (ii) construction of heterojunctions with other semiconductors or plasmonic materials, and (iii) combination with supporters were proposed to tackle their inherent defects, viz., inferior light-harvesting capacity, fast recombination of photogenerated carriers, slow mass transfer and low exposure and uneven dispersion of active sites. Lastly, a critical emphasis was also made on the challenges and prospects of Fe-HPFCs in wastewater treatment, providing valuable guidance to researchers for the reasonable construction of high-performance Fe-HPFCs.

Nanosized Shikonin-Fe(III) Coordination Material for Synergistic Wound Treatment: An Initial Explorative Study

Shikonin (Shik), a natural pigment, has received growing interest in various biomedical fields due to its anti-inflammatory, antitumor, antimicrobial, and antioxidant ability. However, some inherent characteristics of Shik, such as its virulence, low bioavailability, and poor solubility, have limited its biomedical applicability. Here, we reported a facile synthetic method to produce the Shik-iron (III) nanoparticles (Shik-Fe NPs), which could overcome these limitations of Shik. The synthesized Shik-Fe NPs possessed a uniform size range of 110 ± 10 nm, negative surface charges, good water dispersity, and high safety. Iron distributed uniformly inside Shik-Fe NPs, and iron constituted 20% of total mass in PEGylated Shik-Fe NPs. When interacting with activated macrophages, Shik-Fe NPs significantly reduced the level of cellular inflammatory factors, for example, iNOS, IL-1β, and TNF-α. Furthermore, the Shik-Fe NPs demonstrated synergistic anti-inflammation and anti-bacterial properties in vivo, since they could release Fe³⁺ and Shik to eradicate bacteria (Staphylococcus aureus and P. aeruginosa were used as model microbes here) during wound infections and provide full recovery for scald wounds. Collectively, the study established a dual-functional Shik-derived nanoplatform, which could be useful for the treatment of various inflammation-involved diseases.