Metal-organic frameworks doped with metal ions for efficient sterilization: Enhanced photocatalytic activity and photothermal effect

A novel Ag/Bi/Bi2O2CO3 photocatalyst effectively removes antibiotic-resistant bacteria and tetracycline from water under visible light irradiation

Currently, achieving dual applications of Bi2O2CO3-based photocatalysts in photocatalytic degradation and sterilization under visible-light conditions is challenging. In this study, a novel Ag/Bi/Bi2O2CO3 visible-light photocatalyst with bimetallic doping and rich oxygen vacancies was successfully synthesized using a one-pot hydrothermal crystallization method. The existence of oxygen vacancies was verified by X-ray photoelectron spectroscopy (XPS) and Electron spin resonance (ESR) analysis. The experimental results showed that Ag/Bi/Bi2O2CO3 killed ∼100% (log 7) of antibiotic-resistant Escherichia coli (AR-E. coli) within 60 min and degraded 83.81% of tetracycline (TC) within 180 min under visible light irradiation. Moreover, Ag/Bi/Bi2O2CO3 can still remove 61.07% of TC in water after 5 cycles, showing excellent photocatalytic cycle stability and reusability. The possible degradation pathway of TC was determined by liquid chromatography-mass spectrometry. It was found that the main active substances in the photocatalytic disinfection of AR-E. coli were 1O2, h+, and ·OH, while 1O2 was the dominant active species in the photocatalytic degradation of TC. This study presents a promising Bi2O2CO3-based visible light photocatalyst for treating both antibiotics (TC) and antibiotic-resistant bacteria (AR-E. coli) in water.

Inactivation of Listeria monocytogenes, Escherichia coli O157:H7, and Staphylococcus aureus by sequential light-emitting diodes (LEDs) treatment at 365 nm and 420 nm

Frequent outbreaks caused by foodborne pathogens pose long-term risks to consumer health. To proactively reduce the load of pathogenic bacteria during food processing, a novel light-based antibacterial approach was developed by sequential application of 365 nm and 420 nm light-emitting diodes (LEDs). Results demonstrated that after treatment with 365 nm (480 J/cm2) followed by 420 nm (307.2 J/cm2), the reduction of Listeria monocytogenes reached 4.05 ± 0.31 log CFU/mL, significantly higher (an additional 1.8 log CFU/mL, P < 0.05) than cumulative reductions achieved by each 365 nm (2.25 ± 0.92 log CFU/mL) and 420 nm (0.02 ± 0.15 log CFU/mL) treatments. Further analysis revealed that the enhancement in bacterial reduction achieved through the sequential treatment with 365 nm and 420 nm was primarily driven by the exposure time to 365 nm. The inactivation mechanisms were investigated, considering possible photothermal, physical, and oxidative effects. Findings showed that the antibacterial effect of sequential treatment was mainly ascribed to intracellular oxidation generated by reactive oxidative species (ROS), namely hydrogen peroxide and superoxide anion. The antibacterial mechanism of two LEDs may result from the sensitization of bacterial cells to excessive ROS, as evidenced by fluorescent intensity measurements and chemical scavenger assays. This research provides new insight for improving the efficacy of UVA and blue light treatment to control food contamination by Listeria.

Plasma-induced Fe-doped zeolitic imidazolate framework-8 derived P-Fe-N3C for enhanced phenol degradation

Plasma-synergistic catalysis is considered an effective method for degrading aromatic organic pollutants in water. However, the underlying synergistic catalytic mechanism between plasma and catalysts remains poorly understood. Here, we propose a plasma-metal organic frameworks (MOFs) synergistic strategy to investigate the mechanism of plasma-synergistic catalysts for phenol degradation. The results show that Fe-doped Zeolitic Imidazolate Framework-8 (Fex-ZIF8, x = 0, 0.1, 0.2, 0.4) undergoes the plasma-induced transformation into an Fe-N3C structure (P-Fe-N3C), leading to a 4.5-fold enhancement in the phenol degradation rate compared to only plasma discharge. Density functional theory (DFT) calculations indicate that the plasma-induced structural transformation of Fex-ZIF8 promotes the redistribution of point charges and space charges around the Fe center, thereby lowering the activation energy barrier in the rate-determining step (*C6H4(OH)2). These findings not only provide theoretical support for the degradation of water pollutants via plasma-synergistic catalysts but also offer a novel strategy for constructing MOFs-derived materials.

Impact of metal ions on PMS/Cl- disinfection efficacy: Enhancing or impeding microbial inactivation?

Peroxymonosulfate (PMS) is an eco-friendly disinfectant gaining attention. This study examined the influence of metal ions (Co(II), Cu(II), Fe(II)) on PMS disinfection with chloride ions (Cl-) against waterborne microorganisms, encompassing both bacteria and fungal spores. The findings elucidated that metal ions augment the inactivation of bacteria in the PMS/Cl- system while concurrently impeding the inactivation of fungal spores. Specifically, the PMS/Co(II)/Cl- process increased E. coli inactivation rates by 2.25 and 2.75 times compared to PMS/Co(II) and PMS/Cl-, respectively. Conversely, PMS/Me(II)/Cl- generally exhibited a diminished inactivation capacity against the three fungal spores compared to PMS/Cl-, albeit surpassing the efficacy of PMS/Me(II). For instance, the inactivation levels of A. niger by PMS/Cl-, PMS/Cu(II)/Cl-, and PMS/Cu(II) are 4.47-log, 1.92-log, and 0.11-log, respectively. Notably, fungal spores demonstrated a substantially higher resistance to disinfectants compared to bacteria. Differences in microbial susceptibility were linked to cell wall structure, composition, antioxidant defenses, and reactive species generation, such as hydroxyl radicals (•OH), sulfate radicals (SO4•-), and reactive chlorine species (RCS). This study demonstrated the novel and unique phenomenon of metal ions' dual role in modulating the PMS/Cl- disinfection process, which has not been reported before and has important implications for the field of water treatment.

Co-doped Zr-UiO-66-NH2@carboxylated cellulose nanocrystals/PAN membrane for oil/water separation with photocatalysis-PMS synergistic self-cleaning and antibacterial activity

The development of superwetting membranes is a promising approach for separating emulsified oily wastewater. However, challenges such as low flux without external pressure and membrane fouling have hindered membrane performance. Herein, we fabricated a novel nanofibrous membrane by grafting Co-doped Zr-UiO-66-NH2 (UiO(Zr/Co)) nanoparticles onto carboxylated cellulose nanocrystals (CCNC)-polyacrylonitrile (PAN) mixed matrix electrospinning membrane via chemical bonds through EDC/NHS reaction. CCNC served a dual purpose by enhancing membrane hydrophilicity and providing connection points for UiO(Zr/Co). The as-prepared UiO(Zr/Co)@CCNC/PAN exhibited superhydrophilic/underwater superoleophobic and anti-fouling properties. The membrane demonstrated excellent demulsification and gravity-driven separation capabilities for various oil-in-water emulsions, with superior permeation flux (1588-2557 L m-2 h-1) and separation efficiency (above 99 %). Furthermore, UiO (Zr/Co)@CCNC/PAN could activate peroxomonosulfate (PMS) under visible light to remove both high viscous crude oil-fouling and bio-fouling, exhibiting impressive photocatalytic self-cleaning and antibacterial activity. The generation of reactive radicals (O2-, OH and SO4-) and non-radical (1O2) species in UiO(Zr/Co)@CCNC/PAN+PMS system through multiple pathways was confirmed. Additionally, the band structure of UiO(Zr/Co) and synergistic photocatalytic-PMS activation mechanism were investigated. This work provides new insights into the design and fabrication of MOF modified superwetting nanofibrous membrane with inherent bonding, high permeation flux, anti-fouling and self-cleaning properties.

Sustainable and ultrafast antibiotics removal, self-cleaning and disinfection with electroactive metal-organic frameworks/carbon nanotubes membrane

Although conventional nanofiltration (NF) membrane is widely applied in water treatment, it faces the challenges of insufficient selectivity toward emerging contaminants, low permeability and non-sustainable fouling control. Herein, a novel electroactive metal-organic frameworks/carbon nanotubes membrane was constructed by facile and green nanobubbles-mediated non-solvent-induced phase separation (NIPS) strategy for ultrafast antibiotics removal. It presented 3-fold to 100-fold higher permeability (101.3-105.7 L·h-1·m-2·bar-1) without compromising rejection (71.8 %-99.3 %) of common antibiotics (tetracycline, norfloxacin, sulfamethoxazole, sulfamethazine) than most commercial and state-of-the-art NF membranes. The separation mechanism was due to the synergy of loose selective layer with three-dimensional interconnected networks and UiO-66/CNTs with unique pore sieving and charge property. It also presented excellent antibiotics selectivity with high NaCl/tetracycline separation factor of 194 and CuCl2/tetracycline separation factor of 316 for remediation of antibiotics and heavy metal combined pollution. Meanwhile, it possessed efficient anti-fouling, antibacterial and electro-driven self-cleaning ability, which enabled sustainable fouling control and disinfection with short process, low energy and chemical consumption. Furthermore, potential application of UiO-66/CNTs membrane in wastewater reclamation was demonstrated by stable antibiotics rejection, efficient flux recovery and long-term stability over 260 h. This study would provide useful insights into removal of emerging contaminants from water by advanced NF membrane.

Vanadium as a Ti-like mediator boosting electronic transmission in Fe-based MOFs for photocatalytic sterilization

Efficient metal-organic frameworks (MOFs) photocatalytic bactericidal catalysts are urgently needed in water purification. Herein, a Fe-MOF (MIL-88B-NH2(V1Fe5) with promoted electron transport was achieved by vanadium (V) ions doping and V/Fe ratio optimization, showing excellent photocatalytic bactericidal activity againstE. coliunder visible light irradiation (99.92%). The efficient antibacterial mechanism, V as a Ti-like mediator boosting electronic transmission in MIL-88B-NH2(V1Fe5), was revealed by its band structure, transient photocurrent, electrochemical impedance spectroscopy, and scavenger quenching experiments. The enhancement of photocatalytic bactericidal performance of Fe-MOFs by V-ion-doping was confirmed by two other Fe-MOFs, MIL-53-NH2(V1Fe5) and MIL-101-NH2(V1Fe5), with the same metal ions and ligands, both of which have higher performance than the corresponding undoped MOFs. Among them, MIL-88B-NH2(V1Fe5) exhibits the highest photocatalytic bactericidal activity due to its suitable metal clusters ([M(μ3-O)] cluster) and topological structure (three-dimensional rhomboid network structure). This work demonstrated the amplification effect of V ion doping on electron transport in Fe-MOFs photocatalysts.

Engineering valence-mismatched Ti4+ into Fe-based metal-organic-frameworks for enhanced photocatalytic CO2 reduction

A series of low-dose high-valence Ti4+ doped MIL-53-NH2(Fe) photocatalysts were synthesized for visible-light-driven CO2 reduction. The highest CO2-to-CO conversion rate of Ti4+ doped MIL-53-NH2(Fe) was 7.24 mmol g-1 h-1 and the highest CO selectivity was 94% in acetonitrile solvent using [Ru(bpy)3]2+ and triethanolamine.

A review on development and modification strategies of MOFs Z-scheme heterojunction for photocatalytic wastewater treatment, water splitting, and DFT calculations

Increasing water pollution and decreasing energy reserves have emerged as growing concerns for the environment. These pollution are due to the dangerous effects of numerous pollutants on humans and aquatic organisms, such as hydrocarbons, biphenyls, pesticides, dyes, pharmaceuticals, and metal ions. On the other hand, the need for a clean environment, finding alternatives to fossil and renewable fuels is very important. Hydrogen (H2) is regarded as a viable and promising substitute for fossil fuels, and a range of methodologies have been devised to generate this particular source of energy. Metal-organic frameworks (MOFs) are a new generation of nanoporous coordination polymers whose crystal structure is composed of the juxtaposition of organic and inorganic constituent units. Due to their flexible nature, regular structure, and high surface area, these materials have attracted much attention for removing various pollutants from water and wastewater, and water splitting. MOFs Z-scheme heterojunctions have been identified as an economical and eco-friendly method for eliminating pollutants from wastewater systems, and producing H2. Their low-cost synthesis and unique properties increase their application in various energy and environment fields. The heterojunctions possess diverse properties, such as exceptional surface area, making them ideal for degradation and separation. The development and formulation of Z-scheme heterojunctions photocatalytic systems using MOFs, which possess stable and potent redox capability, have emerged as a successful approach for addressing environmental pollution and energy shortages in recent times. Through the utilization of the benefits offered by MOFs Z-scheme heterojunctions photocatalysts, such as efficient separation and migration of charge carriers, extensive spectrum of light absorption, among other advantages, notable enhancements can be attained. This review encompasses the synthesis techniques, structure, and properties of MOFs Z-scheme heterojunctions, and their extensive use in treating various wastewaters, including dyes, pharmaceuticals, and heavy metals, and water splitting. Also, it provides an overview of the mechanisms, pathways, and various theoretical and practical aspects for MOFs Z-scheme heterojunctions. Finally, it thoroughly assesses existing challenges and suggests further research on the promising applications of MOFs Z-scheme in industrial-scale wastewater treatment.

Nanomedicine-based disulfiram and metal ion co-delivery strategies for cancer treatment

Disulfiram (DSF) is a second-line drug for the clinical treatment of alcoholism and has long been proven to be safe for use in clinical practice. In recent years, researchers have discovered the cancer-killing activity of DSF, which is highly dependent on the presence of metal ions, particularly copper ions. Additionally, free DSF is highly unstable and easily degraded within few minutes in blood circulation. Therefore, an ideal DSF formulation should facilitate the co-delivery of metal ions and safeguard the DSF throughout its biological journey before reaching the targeted site. Extensive research have proved that nanotechnology based formulations can effectively realize this goal by strategic encapsulation therapeutic agents within nanoparticle. To be more specific, this is accomplished through precise delivery, coordinated release of metal ions at the tumor site, thereby amplifying its cytotoxic potential. Beyond traditional co-loading techniques, innovative approaches such as DSF-metal complex and metal nanomaterials, have also demonstrated promising results at the animal model stage. This review aims to elucidate the anticancer mechanism associated with DSF and its reliance on metal ions, as well as to provide a comprehensive overview of recent advances in the arena of nanomedicine based co-delivery strategies for DSF and metal ion in the context of cancer therapy.

Bioinspired Photoactive Cu-Halide Coordination Polymers for Reduction Activation and Oxygen Conversion

Natural copper oxygenases provide fundamental principles for catalytic oxidation with kinetically inert molecular oxygen, but it remains a marked challenge to mimic both their structure and function in an entity. Inspired by the CuA enzymatic sites, herein we report two new photoactive binuclear copper-iodine- and bisbenzimidazole-comodified coordination polymers to reproduce the natural oxo-functionalization repertoire in a unique photocatalytic pathway. Under light irradiation, the Cu-halide coordination polymers effectively reduce NHP esters and complete oxygen reduction activation via photoinduced electron transfer for the aerobic oxidative coupling of hydroquinone with terminal alkynes, affording hydroxyl-functionalized ketones with high efficiency and selectivity. This supramolecular approach to developing bioinspired artificial oxygenases that merge transition metal- and photocatalysis supplies a new way to fabricate distinctive photocatalysts with desirable catalytic performances and controllable precise active sites.

Progress of disinfection catalysts in advanced oxidation processes, mechanisms and synergistic antibiotic degradation

Human diseases caused by pathogenic microorganisms make people pay more attention to disinfection. Meanwhile, antibiotics can cause microbial resistance and increase the difficulty of disease treatment, resulting in risk of triggering a vicious circle. Advanced oxidation process (AOPs) has been widely studied in the field of synergistic treatment of the two contaminates. This paper reviews the application of catalytic materials and their modification strategies in the context of AOPs for disinfection and antibiotic degradation. It also delves into the mechanisms of disinfection such as the pathways for microbial inactivation and the related influencing factors, which are essential for understanding the pivotal role of catalytic materials in disinfection principles by AOPs. More importantly, the exploratory research on the combined use of AOPs for disinfection and antibiotic degradation is discussed, and the potential and prospects in this field is highlighted. Finally, the limitations and challenges associated with the application of AOPs in disinfection and antibiotic degradation are summarized. It aims to provide a starting point for future research efforts to facilitate the widespread use of advanced oxidation processes in the field of public health.

Carbonaceous Materials-Based Photothermal Process in Water Treatment: From Originals to Frontier Applications

The photothermal process has attracted considerable attention in water treatment due to its advantages of low energy consumption and high efficiency. In this respect, photothermal materials play a crucial role in the photothermal process. Particularly, carbonaceous materials have emerged as promising candidates for this process because of exceptional photothermal performance. While previous research on carbonaceous materials has primarily focused on photothermal evaporation and sterilization, there is now a growing interest in exploring the potential of photothermal effect-assisted advanced oxidation processes (AOPs). However, the underlying mechanism of the photothermal effect assisted by carbonaceous materials remains unclear. This review aims to provide a comprehensive review of the photothermal process of carbonaceous materials in water treatment. It begins by introducing the photothermal properties of carbonaceous materials, followed by a discussion on strategies for enhancing these properties. Then, the application of carbonaceous materials-based photothermal process for water treatment is summarized. This includes both direct photothermal processes such as photothermal evaporation and sterilization, as well as indirect photothermal processes that assisted AOPs. Meanwhile, various mechanisms assisted by the photothermal effect are summarized. Finally, the challenges and opportunities of using carbonaceous materials-based photothermal processes for water treatment are proposed.

Highly Efficient Photocatalytic Degradation of Tetracycline by Modifying UiO-66 via Different Regulation Strategies

Wastewater containing organic pollutants cause potential harm to the environment and human health. A series of zirconium-organic frameworks (UiO-66) and their composites were synthesized by solvothermal methods, including band gap adjustment, heterojunction construction, and metal ion doping. For the model pollutant tetracycline (TC), all of the prepared catalysts could achieve effective degradation of it. Therein, the degradation efficiency of tetracycline could reach 95% under the UV irradiation with the aid of the catalyst, in which the UiO-66-NDC was modified with P-C3N4. The free radical capture experiments demonstrated that the superoxide radical (•O2-) was the main oxidizing species for the photodegradation of tetracycline. Hence, the improvement strategy of the catalyst would provide some enlightenment for the development of more efficient photocatalysts for the degradation of organic dyes in wastewater.

Improving the intrinsic activity of ultrathin 2D-2D heterostructures by bridge-bonded Ni-O-Ti ligands for efficient oxygen evolution

The integration of ultrathin two-dimensional (2D) semiconductors with other conductive 2D materials to form hybrid electrocatalysts with abundant heterointerfaces can enhance the electrocatalytic activity by facilitating interfacial charge transfer. However, the hybrid electrocatalysts with weak interfacial bonding have limited effect on the electrocatalytic performance because the intrinsic activity of interfacial sites cannot be altered by weak interfacial interactions. As a proof-of-concept, we design ultrathin 2D-2D heterostructures with bridge-bonded Ni-O-Ti ligands based on single-layered Ti₃C₂T_xMXene and metal hydroxides, and further reveal the structure-activity correlation between interfacial bonding and electrocatalytic oxygen evolution reaction by combining theoretical and experimental studies. Density functional theory calculations reveal the modulation of the electronic structure of interfacial metal sites after the formation of bridged interfacial Ni-O-Ti bonding. Compared with the hydrogen-bond-linked heterostructure, the ultrathin 2D-2D heterostructure with bridge-bonded Ni-O-Ti ligands shows enhanced intrinsic activity and stability towards electrocatalytic oxygen evolution with a very low overpotential of 205 mV at 10 mA cm^-2and the long-term durability. This work provides a new understanding and approach for the design and development of 2D hybrid catalysts with highly efficient electrocatalytic activity.

Spatially Separated Redox Cocatalysts on Ferroelectric Nanoplates for Improved Piezophotocatalytic CO2 Reduction and H2O Oxidation

Utilizing solar and mechanical vibration energy for catalytic CO₂ reduction and H₂O oxidation is emerging as a promising way to simultaneously generate renewable energy and mitigate climate change, making it possible to integrate two energy resources into a reaction system for artificial piezophotosynthesis. However, the practical applications are hindered by undesirable charge recombination and sluggish surface reaction in the photocatalytic and piezocatalytic processes. This study proposes a dual cocatalyst strategy to overcome these obstacles and improve the piezophotocatalytic performance of ferroelectrics in overall redox reactions. With the photodeposition of AuCu reduction and MnO_x oxidation cocatalysts on oppositely poled facets of PbTiO₃ nanoplates, band bending occurs along with the formation of built-in electric fields on the semiconductor-cocatalyst interfaces, which, together with an intrinsic ferroelectric field, piezoelectric polarization field, and band tilting in the bulk of PbTiO₃, provide strong driving forces for the directional drift of piezo- and photogenerated electrons and holes toward AuCu and MnO_x, respectively. Besides, AuCu and MnO_x enrich the active sites for surface reactions, significantly reducing the rate-determining barrier for CO₂-to-CO and H₂O-to-O₂ transformation, respectively. Benefiting from these features, AuCu/PbTiO₃/MnO_x delivers remarkably improved charge separation efficiencies and significantly enhanced piezophotocatalytic activities in CO and O₂ generation. This strategy opens a door for the better coupling of photocatalysis and piezocatalysis to promote the conversion of CO₂ with H₂O.

Functionalized MOF-Based Photocatalysts for CO2 Reduction

Metal-organic frameworks (MOFs) materials have become a research forefront in the field of photocatalytic CO₂ reduction attributed to their ultra-high specific surface area, adjustable structure, and abundant catalytic active sites. Particularly, MOFs can be facilely tuned to match CO₂ photoreduction by utilizing post-modification of metal nodes, functionalization of organic linkers, and combination with other active materials. Herein, the recent advances in the construction strategy of MOF-based photocatalysts materials for CO₂ reduction are highlighted. Some systematic modification strategies on MOF-based photocatalysts are also discussed, such as modification of metal sites and organic ligands, construction of heterojunction, introduction of single/dual-atom, and strain engineering. Finally, the future development directions of MOF-based photocatalysts in the field of CO₂ reduction are presented.