Engineering highly effective and stable nanocomposite photocatalyst based on NH2-MIL-125 encirclement with Ag3PO4 nanoparticles

Decoration of viscose fibers with silver nanoparticle-based titanium-organic framework for use in environmental applications

To effectively remove pharmaceuticals, nitroaromatic compounds, and dyes from wastewater, an efficient multifunctional material was created based on silver nanoparticles (Ag) and MIL-125-NH2 (MOF) immobilized on viscose fibers (VF) as a support substrate. Firstly, silver nanoparticles (Ag) were immobilized on the surface of viscose fibers (VF) via in situ synthesis using trisodium citrate (TSC) as a reducing agent to create (VF-Ag). Then, VF and VF-Ag were decorated with the titanium metal-organic framework MIL-125-NH2 (MOF) to create VF-MOF and VF-Ag-MOF. The influence of VF-Ag, VF-MOF, and VF-Ag-MOF on the sonocatalytic or sonophotocatalytic degradation of sulfa drugs was investigated. The results show that VF-Ag-MOF showed excellent sonocatalytic and sonophotocatalytic activity towards the degradation of sulfa drugs compared to VF-Ag and VF-MOF. Furthermore, sonophotodegradation showed a dramatic enhancement in the efficiency of degradation of sulfa drugs compared to sonodegradation. The sonophotodegradation degradation percentage of sulfanilamide, sulfadiazine, and sulfamethazine drugs in the presence of VF-Ag-MOF was 65, 90, and 95 after 45 min of ultrasonic and visible light irradiation. The catalytic activity of VF-Ag, VF-MOF, and VF-Ag-MOF was evaluated through the conversion of p-nitrophenol (4-NP) to p-aminophenol (4-AP). The results demonstrate that VF-Ag-MOF had the highest catalytic activity, followed by VF-Ag and VF-MOF. The conversion percentage of 4-NP to 4-AP was 69%. The catalytic or photocatalytic effects of VF-Ag, VF-MOF, and VF-Ag-MOF on the elimination of methylene blue (MB) dye were investigated. The results demonstrate that VF-Ag-MOF showed high efficiency in removing the MB dye through the reduction (65%) or photodegradation (71%) after 60 min. VF-Ag-MOF composites structure-activity relationships represent that doping within silver NPs enhanced the photocatalytic activity of MIL-125-NH2, which could be explained as follows: (i) Due to the formation of a Schottky barrier at the junction between MIL-125-NH2 and Ag NPs, the photogenerated electrons in the conduction band of MIL-125-NH2 were supposed to be quickly transferred to the valence band of the Ag NPs, and subsequently, the electrons were transferred to the conduction band of Ag NPs. This considerable electron transferring process, which is reported as Z scheme heterojunction, can efficiently suppress the recombination of electron/hole pairs in VF-Ag-MIL-125-NH2 composites. (ii) Sufficient separation between the photogenerated charge carriers (holes and electrons) and avoiding their recombination enhanced the photocatalytic activity of composites.

Novel SnO2@Cu3(BTC)2 Composites as a Highly Efficient Photocatalyst and Fluorescent Sensor

A novel SnO2@Cu3(BTC)2 composite was synthesized using a quick and affordable bottom-up approach via impregnation of SnO2 nanoparticles into the porous Cu3(BTC)2 metal-organic framework (MOF). This composite material is characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD) spectra, scanning electron microscope (SEM) analysis, and energy-dispersive X-ray spectroscopy (EDS) analysis. SnO2@Cu3(BTC)2 degraded the methylene blue (MB) dye within 80 min under sunlight with a maximum degradation efficiency of 85.12%. This composite easily recyclable up to five cycles with the retention of its MB degradation efficiency. Moreover, SnO2@Cu3(BTC)2 can be also used efficiently for fast sensing of 2,4,6-trinitrophenol (TNP) in water with noticeable turn-off quenching response. Its limits of detection (LOD) for TNP was 2.82 µM with enhanced selectivity toward TNP (over other NACs) as verified by competitive nitro explosive tests. Density functional theory (DFT) calculations and spectral overlap were used to assess the sensing mechanism. This composite fluorescent sensing system for TNP are demonstrated to have high selectivity and sensitivity. Our findings imply that the prepared low cost SnO2@Cu3(BTC)2 composite can be used as a superior fluorescence sensor and photo catalyst for large scale industrial applications.

Ag Nanoparticle and Ti-MOF Cooperativity for Efficient Inactivation of E. coli in Water

Because of the limitations of traditional chlorine-based bactericidal water treatment, such as the formation of disinfection byproducts (DBPs) and resistance to chlorine, novel approaches and materials are required for effective disinfection of water. This study focuses on the development of a new sterilization material, Ag/NH2-MIL-125(Ti), which was designed to effectively inactivate Escherichia coli in water. The effectiveness of the as-designed material stems from the synergistic interactions between Ag nanoparticles (NPs) and photoactive metal-organic frameworks (MOFs). In this complex material, the MOFs play a critical role in dispersing and isolating the Ag NPs, thus preventing undesirable aggregation during bacterial inactivation. Simultaneously, Ag NPs enhance the photocatalytic performance of the MOFs. Sterilization experiments demonstrate the remarkable rapid E. coli inactivation performance of Ag/NH2-MIL-125(Ti) under illuminated and nonilluminated conditions. Within 25 min of visible light exposure, the as-prepared material achieves a >7-log E. coli reduction. In addition, Ag/NH2-MIL-125(Ti) efficiently decomposes acetic acid, which is the main DBP precursor, under visible light irradiation. Mechanistic investigations revealed that •O2- and h+ were the primary active substances responsible for the inactivation of E. coli and the decomposition of acetic acid, respectively.

Zeolitic imidazolate frameworks as light-responsive oxidase-like mimics for the determination of adenosine triphosphate and discrimination of phenolic pollutants

In this study, 3,3',5,5'-tetramethylbenzidine (TMB) was selected as a chromogenic substrate to evaluate the light-responsive oxidase-like activity of different zeolitic imidazolate frameworks (ZIFs). The synthesized ZIFs were systematically characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. Several main operational parameters, including ZIFs and TMB concentrations, pH value, radiation time, and working current, in the reaction process were optimized. The kinetic measurement results show that ZIF-90 exhibits higher affinity to the substrate than horseradish peroxidase. Furthermore, given that adenosine triphosphate (ATP) can specifically combine with Zn²⁺ binding site and destroy the structure of ZIF-90, a specific and sensitive colorimetric method was established for the quantitative detection of ATP within the range 10 - 240 μM. In addition, on the basis that phenolic pollutants can impact the reaction kinetics diversely on different ZIFs, a sensor array was constructed and successfully applied to differentiate five phenolic pollutants in lake water samples. This work is expected to shed light on the establishment of ZIF-based light-responsive oxidase-like nanozymes for the highly selective colorimetric detection and sensor array.

Advancements in visible light responsive MOF composites for photocatalytic decontamination of textile wastewater: A review

Heterogeneous photocatalysis using metal-organic frameworks (MOFs) is expected to provide a pivotal solution for the remediation of toxic dyes and heavy metals from textile wastewater. However, MOFs often suffer from a low removal efficiency, due to the rapid recombination between holes and electrons, generated upon photoexcitation. Additionally, the MOFs exhibit poor water stability, which restricts their large-scale application. In this regard, various approaches (i.e. doping of metal nanoparticle, semiconductor, quantum dot, and ligand functionalization) have been adopted for the formation of multifunctional composites. The MOF-composites possess suitable photochemical, surface, optical, and electronic properties, resulting in enhanced water stability, visible light absorption, and reduced recombination between photogenerated species. This comprehensive review targets to provide an insight into the synthesis and subsequent application of various MOF composites for photocatalytic removal of organic contaminants (dyes) and inorganic (Cr(VI)) contaminants from water. MOFs/graphene oxide composites possess improved surface area and reusability whereas noble metal incorporated MOFs composites suffer from photocorrosion and are relatively costly. Zr and Ti based MOFs exhibit tuning from UV to visible light response and surpass the poor water stability upon binary/ternary composite formation. The role of the dopants in enhancing the efficiency of the composites; the effect of influencing factors such as solution pH, pollutant concentration; the mechanism, and the kinetics of reactions have been outlined. In spite of many advancements, the article also summarizes some roadblocks that need to be unraveled to achieve the energy-water-environment nexus and scope for future breakthrough research in this field.

Ag3PO4-based photocatalysts and their application in organic-polluted wastewater treatment

Semiconductor photocatalysis technology has shown great potential in the field of organic pollutant removal, as it can use clean and pollution-free solar energy as driving force. The discovery of silver phosphate (Ag₃PO₄) is a major breakthrough in the field of visible light responsive semiconductor photocatalysis due to its robust capacity to absorb visible light < 520 nm. Furthermore, the holes produced in Ag₃PO₄ under light excitation possess a strong oxidation ability. However, the strong oxidation activity of Ag₃PO₄ is only achieved in the presence of electron sacrifice agents. Otherwise, photocorrosion would greatly reduce the reuse efficiency of Ag₃PO₄. This review thus focuses on the structural characteristics and preparation methods of Ag₃PO₄. Particularly, the recent advances in noble metal deposition, ion doping, and semiconductor coupling, as well as methods of magnetic composite modification for the improvement of catalytic activity and recycling efficiency of Ag₃PO₄-based catalysts, were also discussed, and all of these measures could enhance the catalytic performance of Ag₃PO₄ toward organic pollutants degradation. Additionally, some potential modification methods for Ag₃PO₄ were also proposed. This review thus provides insights into the advantages and disadvantages of the application of Ag₃PO₄ in the field of photocatalysis, clarifies the photocorrosion essence of Ag₃PO₄, and reveals the means to improve photocatalytic activity and stability of Ag₃PO₄. Furthermore, it provides a theoretical and methodological basis for studying Ag₃PO₄-based photocatalyst and also compiles valuable information regarding the photocatalytic treatment of organic polluted wastewater.

A super-hydrophilic NH2-MIL-125 composite film with dopamine-modified graphene oxide is used for water treatment

It is always concerning about how to remove oil–water emulsions and dyes simultaneously and how to find a suitable separation film.

Recent Improvement Strategies on Metal-Organic Frameworks as Adsorbent, Catalyst, and Membrane for Wastewater Treatment

The accumulation of pollutants in water is dangerous for the environment and human lives. Some of them are considered as persistent organic pollutants (POPs) that cannot be eliminated from wastewater effluent. Thus, many researchers have devoted their efforts to improving the existing technology or providing an alternative strategy to solve this environmental problem. One of the attractive materials for this purpose are metal-organic frameworks (MOFs) due to their superior high surface area, high porosity, and the tunable features of their structures and function. This review provides an up-to-date and comprehensive description of MOFs and their crucial role as adsorbent, catalyst, and membrane in wastewater treatment. This study also highlighted several strategies to improve their capability to remove pollutants from water effluent.

Observable removal of pharmaceutical residues by highly porous photoactive cellulose acetate@MIL-MOF film

Pharmaceutical products are used tremendously worldwide and subsequently released into wastewater even at very low concentration caused serious environmental problem due to their high activity. Therefore, the present work focuses on remarkable removal of paracetamol as one from the most used pharmaceutical intermediates, by using porous film based on cellulose acetate@metal organic framework (CA@Ti-MIL-NH₂). The film was designed to achieve extreme removal of paracetamol by action of both of adsorption and degradation. Metal organic frame work was directly synthesized and inserted within the pre-prepared porous CA film to obtain porous CA@Ti-MIL-NH₂ film. The synthesized films were applied in adsorption and photo-degradation of paracetamol separately and together. Due to the photocatalytic activity of Ti-MIL-NH_2, the photo-degradation of paracetamol in visible-light was much effective and considerably high degradation of paracetamol was observed (k₁ = 760.0 m^-1) comparing to the adsorption (k₁ = 160.0 m^-1). The overall removal of paracetamol was significantly enlarged from 82.7 mg/g for CA film to 519.1 mg/g for porous CA@Ti-MIL-NH₂ film. The used film exhibited quite good reusability and the removal of paracetamol was lowered from 96% to 85% after 5 regeneration cycles. Results of total organic carbon confirmed that paracetamol was fully degraded to CO₂ and water.

Photocatalytic Activities of FeNbO4/NH2-MIL-125(Ti) Composites toward the Cycloaddition of CO2 to Propylene Oxide

Photocatalytic utilization of CO2 in the production of value-added chemicals has presented a recent green alternative for CO2 fixation. In this regard, three FeNbO4/NH2-MIL-125(Ti) composites of different mole ratios were synthesized, characterized using Powder X-ray diffraction (PXRD), UV-vis diffuse reflectance spectroscopy (UV-Vis DRS), Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX). PXRD patterns confirm the co-existence of the parent components in the prepared composites. Moreover, the surface area increased as the mole percent of NH2-MIL-125(Ti) in the composites increased due to the large surface area of NH2-MIL-125(Ti). Prepared composites were investigated for the photocatalytic insertion of CO2 into propylene oxide. FeNbO4(75%)/NH2-MIL-125(Ti)(25%) showed the highest percent yield of 52% compared to the other two composites. Results demonstrate the cooperative mechanism between FeNbO4 and NH2-MIL-125(Ti) and that the reaction proceeded photocatalytically.

Construction of NH2-MIL-125(Ti)/CdS Z-scheme heterojunction for efficient photocatalytic H2 evolution

Designing efficient semiconductor-based photocatalysts for hydrogen production is a challenging but promising prospect in energy conversion. Herein, a novel Z-scheme CdS/NH₂-MIL-125(Ti) heterojunction is successfully fabricated through a facile solvethermal method. The detailed characterizations reveal that CdS nanoparticles are in-suit archored on NH₂-MIL-125(Ti) nanoplates. Benefited from the intrinsic band alignment and intimate contact of two species, this established structure gives a positive effect regarding charge separation. In consequence, the optimal CdS/NH₂-MIL-125(Ti) nanocomposites exhibit excellent photocatalytic performance with hydrogen evolution rate of 6.62 mmol·h^-1·g^-1 under visible light illumination, which was 3.5 times higher than that of the pristine CdS. We believe that this work will provide a new avenue to develop high-efficiency heterojunction catalyst for solar-driven energy conversions and other application.

Facile synthesis of a novel Ag3PO4/MIL-100(Fe) Z-scheme photocatalyst for enhancing tetracycline degradation under visible light

In this work, a novel visible light-driven heterostructure Ag₃PO₄/MIL-100(Fe) composite photocatalyst was successfully synthesized via facile chemical deposition method at room temperature. Especially when the mass ratio of Ag₃PO₄ was 20% of MIL-100(Fe) (APM-2), it displayed the best photocatalytic performance, for which the degradation rate of tetracycline (TC) in conventional environment was 6.8 times higher than that of bare MIL-100(Fe). In addition, the effects of the initial concentration and pH of the solution on the degradation of tetracycline were also studied, and the results showed that the degradation of tetracycline was more favorable in a weakly alkaline environment. The excellent performance of Ag₃PO₄/MIL-100(Fe) composites was attributed to the fact that on the basis of having adequate photocatalytic active sites, modifying MIL-100(Fe) with an appropriate amount of Ag₃PO₄ particles can more effectively separate photogenerated electron-hole pairs. Five cycles of experiments showed that APM-2 has good photostability. Lastly, it was proved through quenching experiments that •O₂^-, h⁺, and •OH all played corresponding roles in the degradation process, and a possible Z-scheme heterostructure photocatalytic degradation mechanism was proposed.

Recent advances in MOF-based photocatalysis: environmental remediation under visible light

Highly photoactive MOFs can be engineered via various strategies for the purpose of extended visible light absorption, more efficient generation, separation and transfer of charge carriers, as well as good recyclability.

Controllable Synthesis of Porous Cu-BTC@polymer Composite Beads for Iodine Capture

The efficient and safe capture of radioactive iodine (¹²⁹I or ¹³¹I) is of great significance in nuclear waste disposal. Here, we report millimeter-scale poly(ether sulfone) composite beads loaded with porous Cu-BTC [Cu₃(BTC)₂, BTC = 1,3,5-benzenetricarboxylate] (Cu-BTC@PES), prepared by a phase inversion method for the removal of volatile iodine. Three kinds of Cu-BTC@PES composite beads were obtained with different Cu-BTC contents of 48.6, 60.2, and 71.9%, respectively. While maintaining crystallinity, the composite beads exhibited higher I₂ vapor adsorption capacity (639 mg/g) in the form of iodine molecules. The iodine absorption up to 260 mg/g and the adsorption was followed Langmuir isotherm and pseudo-second-order kinetic model. Furthermore, the composite beads can still absorb more than 85% of iodine after 3 cycles of regeneration with excellent recyclability. The resulting Cu-BTC@PES composite beads show great potential for the sustainable removal of radioactive iodine.

In situ deposition of Ag/AgCl on the surface of magnetic metal-organic framework nanocomposite and its application for the visible-light photocatalytic degradation of Rhodamine dye

Herein, NH₂-MIL-125(Ti) (NMT) as one of the known stable metal-organic frameworks (MOFs) in aqueous solution was successfully magnetized with CoFe₂O₄ nanoparticles through the hydrothermal method. The Ag/AgCl as a plasmonic photocatalyst was assembled on the CoFe₂O₄/NMT (CFNMT) at room temperature by in situ deposition, and photo-reduction methods to improve the photocatalytic activity of CFNMT under LED visible light. The prepared materials were fully characterized by SEM/EDX, TEM, FTIR, XRD, UV-DRS, and VSM analysis. Rhodamin B (RhB) was selected as the pollutant model. The results showed that the Ag/AgCl@CFNMT had super-fast degradation ability of RhB molecule due to the synergetic effect between Ag/AgCl and CFNMT in comparison with NMT and CFNMT. The introduced Ag/AgCl on the surface of CFNMT increased absorption of photons in the visible region and enhanced the transfer and separation of the produced charge on the contact area between Ag/AgCl and CFNMT. Also, after seven times recycling, besides the simple magnetic separation of Ag/AgCl@CFNMT from liquid media, the composite still showed high photodegradation ability (89%).

Tetrahedral UMOFNs/Ag3PO4 Core-Shell Photocatalysts for Enhanced Photocatalytic Activity under Visible Light

A new visible-light-responsive tetrahedral ultrathin metal-organic framework nanosheet (UMOFNs)/Ag₃PO₄ composite photocatalyst with a core-shell structure was readily synthesized by sonication in an organic solvent. Characterization methods for the photocatalyst included X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and UV-vis diffuse reflectance spectroscopy. The XRD patterns of the composite photocatalyst before and after visible-light irradiation demonstrated that trace amounts of Ag ions in the composite photocatalyst easily transformed into Ag nanoparticles, which play a role in promoting charge separation at the interface of a heterojunction. The UMOFNs/Ag₃PO₄ composite photocatalyst showed higher photocatalytic activity for the photodegradation of 2-chlorophenol (2-CP) under visible-light irradiation (>420 nm) than Ag₃PO₄. The complete degradation of 2-CP was achieved in 7 min using the tetrahedral UMOFNs/Ag₃PO₄ core-shell photocatalyst, and the apparent reaction rate was approximately 26 times higher than that of pure Ag₃PO₄. Further, a scavenger experiment showed h⁺ and O₂ ^•- were the major reactive species involved in the photocatalytic reaction system. This enhanced photocatalytic activity results from the efficient separation of photoinduced electron-hole pairs and the increase of interface area between Ag₃PO₄, UMOFNs, and the Ag nanoparticles.

Antimicrobial cellulosic textiles based on organic compounds

Healthy body is one of the principle requirements of human beings, but the highly rated growth of harmful pathogens has challenged researchers for investigation of antimicrobial reagents. Infection of textile materials is a result of microbial adherence on the surface, and it is one of the vital clinical complications, which causes a high rate of mortality. New challenges as well as new opportunities in manufacturing of antimicrobial cellulosic textiles are the future concerns for textile and apparel industry. The major applications of antimicrobial textile could be ascribed according consumer demands, represented in more comfort, easy care, health, and durable to laundering. Such numerous properties could be achieved by the development of innovative methodologies with various finishing agents. Thus, the current review introduced an overview for the application of recent organic antimicrobial reagents in cellulosic textile finishing. The organic reagents are classified into two main categories; natural (chitosan, cyclodextrins and natural dyes) and synthetic (quaternary ammonium salts, triclosan, halogenated phenols and metal organic frameworks). The interaction between cellulose and such reagents, biological action mechanisms and factors affecting biocidal actions are all presented. For improvement of the durability and mechanical properties, pre-activation of cellulosic textile or using of cross-linkers is properly performed.

Ternary dual Z-scheme graphitic carbon nitride/ultrathin metal–organic framework nanosheet/Ag3PO4 photocatalysts for boosted photocatalytic performance under visible light

The enhanced photocatalytic activity of CN10UA results from fast charge transport through dual Z-scheme channels.

Immobilization ofl-methioninase on a zirconium-based metal–organic framework as an anticancer agent

A new composite (METase@UiO-66) was prepared froml-methioninase and UiO-66-(COOH), which exhibited enhanced thermostability, pH and storage lifetime compared tol-methioninase. Moreover,in vivoexperiments showed that the drug inhibited tumor growth in mice.

Metal Organic Frameworks Based Materials for Heterogeneous Photocatalysis

The increase in environmental pollution due to the excessive use of fossil fuels has prompted the development of alternative and sustainable energy sources. As an abundant and sustainable energy, solar energy represents the most attractive and promising clean energy source for replacing fossil fuels. Metal organic frameworks (MOFs) are easily constructed and can be tailored towards favorable photocatalytic properties in pollution degradation, organic transformations, CO₂ reduction and water splitting. In this review, we first summarize the different roles of MOF materials in the photoredox chemical systems. Then, the typical applications of MOF materials in heterogeneous photocatalysis are discussed in detail. Finally, the challenges and opportunities in this promising field are evaluated.

Photocatalytic Degradation of Diclofenac by Hydroxyapatite⁻TiO₂ Composite Material: Identification of Transformation Products and Assessment of Toxicity

Diclofenac (DCF) is one of the most detected pharmaceuticals in environmental water matrices and is known to be recalcitrant to conventional wastewater treatment plants. In this study, degradation of DCF was performed in water by photolysis and photocatalysis using a new synthetized photocatalyst based on hydroxyapatite and TiO₂ (HApTi). A degradation of 95% of the target compound was achieved in 24 h by a photocatalytic treatment employing the HApTi catalyst in comparison to only 60% removal by the photolytic process. The investigation of photo-transformation products was performed by means of UPLC-QTOF/MS/MS, and for 14 detected compounds in samples collected during treatment with HApTi, the chemical structure was proposed. The determination of transformation product (TP) toxicity was performed by using different assays: Daphnia magna acute toxicity test, Toxi-ChromoTest, and Lactuca sativa and Solanum lycopersicum germination inhibition test. Overall, the toxicity of the samples obtained from the photocatalytic experiment with HApTi decreased at the end of the treatment, showing the potential applicability of the catalyst for the removal of diclofenac and the detoxification of water matrices.