Metal-organic framework-derived nanomaterials in environment related fields: Fundamentals, properties and applications

Electrochemical sensing mechanisms of neonicotinoid pesticides and recent progress in utilizing functional materials for electrochemical detection platforms

The excessive residue of neonicotinoid pesticides in the environment and food poses a severe threat to human health, necessitating the urgent development of a sensitive and efficient method for detecting trace amounts of these pesticides. Electrochemical sensors, characterized by their simplicity of operation, rapid response, low cost, strong selectivity, and high feasibility, have garnered significant attention for their immense potential in swiftly detecting trace target molecules. The detection capability of electrochemical sensors primarily relies on the catalytic activity of electrode materials towards the target analyte, efficient loading of biomolecular functionalities, and the effective conversion of interactions between the target analyte and its receptor into electrical signals. Electrode materials with superior performance play a crucial role in enhancing the detection capability of electrochemical sensors. With the continuous advancement of nanotechnology, particularly the widespread application of novel functional materials, there is paramount significance in broadening the applicability and expanding the detection range of pesticide sensors. This comprehensive review encapsulates the electrochemical detection mechanisms of neonicotinoid pesticides, providing detailed insights into the outstanding roles, advantages, and limitations of functional materials such as carbon-based materials, metal-organic framework materials, supramolecular materials, metal-based nanomaterials, as well as molecular imprinted materials, antibodies/antigens, and aptamers as molecular recognition elements in the construction of electrochemical sensors for neonicotinoid pesticides. Furthermore, prospects and challenges facing various electrochemical sensors based on functional materials for neonicotinoid pesticides are discussed, providing valuable insights for the future development and application of biosensors for simplified on-site detection of agricultural residues.

AgAu-modified quasi-MIL-53 hybrid nanozymes with triple enzyme-like activities for boosting biocatalytic disinfection

Metal-organic frameworks (MOFs) have great potential for combating pathogenic bacterial infections and are expected to become an alternative to antibiotics. However, organic linkers obstruct and saturate the inorganic nodes of MOF structures, making it challenging to utilize the applied potential of metal centers. Here, we combined controlled ligand decarboxylation with noble metal nanoparticles to rationally remodel MIL-53, resulting in a hybrid nanozyme (AgAu@QMIL-53, AAQM) with excellent multiple enzyme-like activities that both eradicate bacteria and promote diabetic wound healing. Specifically, benefitting from oxidase (OXD)-like and peroxidase (POD)-like activities, AAQM converts oxygen (O2) and hydrogen peroxide (H2O2) into superoxide anion radicals (O2-) and hydroxyl radicals (OH) to eradicate bacteria. In in vitro antibacterial experiments, AAQM exhibited favorable killing efficacy against Pseudomonas aeruginosa (P. aeruginosa) and methicillin-resistant Staphylococcus aureus (MRSA) (>99 %). Notably, due to its superoxide (SOD)-like activity and outstanding reactive nitrogen species (RNS) elimination capacity, AAQM can produce adequate O2 and alleviate oxidative stress in diabetic wounds. Benefiting from the rational modification of MIL-53, the synthesized hybrid nanozyme can effectively kill bacteria while alleviating oxidative stress and ultimately promote infected diabetic wound healing. Overall, this biomimetic enzyme-catalyzed strategy will bring enlightenment to the design of self-antibacterial agents for efficient disinfection and wound healing simultaneously.

Microwave-assisted synthesis and development of novel penicillinoate@copper metal-organic frameworks as a potent antibacterial agent

Recently, nanoscience, especially metal-organic frameworks (MOFs), has been used to increase the effectiveness and properties of drugs. In this study, by using microwave irradiation; penicillin, which is a known antibiotic; and copper metal-organic frameworks (Cu-MOFs), a new penicillinoate@copper metal-organic framework (penicillinoate@Cu-MOF) was synthesized. The structure and characterization of the newly synthesized compound were determined using FT-IR spectrums, EDAX analysis, elemental analysis, XRD patterns, SEM images, nitrogen adsorption/desorption curves, and TGA curve. Then, its antimicrobial effects were evaluated on numerous Gram-positive and Gram-negative bacterial strains and were compared with those of penicillin and gentamicin. In continuation of the biological activities, antioxidant tests were performed on the compounds using the DPPH method. For biological activities, the synthesized penicillinoate@Cu-MOF is much more effective than penicillin and Cu-MOF. The loading of penicillin on the nanostructure and the presence of copper in the final composition can be attributed to the high antibiotic properties of the synthesized composition.

Mechanisms of interaction between metal-organic framework-based material and persulfate in degradation of organic contaminants (OCs): Activation, reactive oxygen generation, conversion, and oxidation

Metal-organic frameworks (MOFs)-based materials have been of great public interest in persulfate (PS)-based catalytic oxidation for wastewater purification, because of their excellent performance and selectiveness in organic contaminants (OCs) removal in complex water environments. The formation, fountainhead and reaction mechanism of reactive oxygen species (ROSs) in PS-based catalytic oxidation are crucial for understanding the principles of PS activation and the degradation mechanism of OCs. In the paper, we presented the quantitative structure-activity relationship (QSAR) of MOFs-based materials for PS activation, including the relationship of structure and removal efficiency, active sites and ROSs as well as OCs. In various MOFs-based materials, there are many factors will affect their performances. We discussed how various surface modification projects affected the characteristics of MOFs-based materials used in PS activation. Moreover, we revealed the process of ROSs generation by active sites and the oxidation of OCs by ROSs from the micro level. At the end of this review, we putted forward an outlook on the development trends and faced challenges of MOFs for PS-based catalytic oxidation. Generally, this review aims to clarify the formation mechanisms of ROSs via the active sites on the MOFs and the reaction mechanism between ROSs and OCs, which is helpful for reader to better understand the QSAR in various MOFs/PS systems.

Layer Growth Inhibiting Strategy for Superior-Loading Atomic Metal Sites on Ultrathin Layered Double Hydroxides as the Efficient Chemiluminescence Probes

Owing to the remarkable catalytic attributes, single-atom catalysts (SACs) have exhibited promising application prospects as the substitutes of natural enzymes. However, the low loading amount of atomic sites on typical SACs (no more than 5 wt %) significantly restricts their increased capability. Hereby, a layer growth inhibitor protocol was attempted to optimize anchoring isolated Co atoms efficiently on ultrathin monolayer layered double hydroxides (LDHs). Superior to the conventional multiple-layer LDHs, the synthesized monolayer LDHs (7.29 nm-thick) served as the emerging support for dispersing substantial active sites and featured a dramatic loading content of 32.5 wt %. Through X-ray absorption spectroscopy, the atomically dispersed active centers on Co SACs were verified as Co-N4 moieties. The results of radical scavenger experiments and electron paramagnetic resonance spectroscopy showed that Co SACs were favorable to the high yield of reactive oxygen species originating from the decomposition of H2O2. Therefore, Co SACs functioned as a sensitive enhancer to drastically boost the luminol-H2O2 chemiluminescence intensity by ∼4713-fold, which excelled drastically over these previously reported SACs. Furthermore, Co SACs were adopted as chemiluminescent probes for the quantitation of chlorothalonil, wherein a low detection limit of 49 pg mL-1 (3σ) was achieved. Additionally, the successful application in recovery trials demonstrated the favorable feasibility of Co SACs. The facile layer growth inhibitor protocol affords SACs with improved loading properties and even superior catalytic performances for sensitive luminescent bioassays.

Facile synthesis of Co-Fe layered double hydroxide nanosheets wrapped on Ni-doped nanoporous carbon nanorods for oxygen evolution reaction

Owing to the high demand for clean and renewable energy technologies, several studies have focused on developing economically feasible, highly effective, and stable non-precious electrocatalysts for promoting the oxygen evolution reaction (OER). This development has stimulated an expansion of investigative quests and indicated the importance of advancing electrocatalytic research in this field. Through a facile and efficient method, Ni nanoparticles were uniformly embedded into nanoporous carbon nanorods (Ni-NCN), which are subsequently electrodeposited on CoFe-layered double hydroxide (LDH) nanosheets to produce highly efficient Ni-NCN/CoFe-LDH composites used for OER. The composite exhibited excellent catalytic activity toward OER owing to its low overpotential (ƞ10 mA = 280 mV), small Tafel slope (42 mV dec-1), and excellent durability. The Ni-NCN/CoFe-LDH catalyst exhibited higher OER activity owing to its uniformly dispersed Ni nanoparticles, large specific surface area, enhanced electron transport, and synergistic effect of multiple composites. Additionally, the enhanced synergistic effect of Ni-NCN promoted higher OER performance compared with Ni-undoped carbon nanorod/LDH, indicating that the Ni dopant and LDH significantly contributed to the overall OER performance. The synergistic effect of multiple composites significantly contributed to the excellent OER performance, indicating their potential as OER catalyst.

Current advances in the detection and removal of organic arsenic by metal-organic frameworks

Arsenic (As) is a highly toxic heavy metal and has been widely concerned for its hazardous environmental impact. Aromatic organic arsenic (AOCs) has been frequently used as an animal supplement to enhance feed utilization and prevent dysentery. The majority of organic arsenic could be discharged from the body and evolve as highly toxic inorganic arsenic that is hazardous to the environment and human health via biological conversion, photodegradation, and photo-oxidation. Current environmental issues necessitate the development and application of multifunctional porous materials in environmental remediation. Compared to the conventional adsorbent, such as activated carbon and zeolite, metal-organic frameworks (MOFs) exhibit a number of advantages, including simple synthesis, wide variety, simple modulation of pore size, large specific surface area, excellent chemical stability, and easy modification. In recent years, numerous scientists have investigated MOFs related materials involved with organic arsenic. These studies can be divided into three categories: detection of organic arsenic by MOFs, adsorption to remove organic arsenic by MOFs, and catalytic removal of organic arsenic by MOFs. Here, we conduct a critical analysis of current research findings and knowledge pertaining to the structural characteristics, application methods, removal properties, interaction mechanisms, and spectral analysis of MOFs. We summarized the application of MOFs in organic arsenic detection, adsorption, and catalytic degradation. Other arsenic removal technologies and conventional substances are also being investigated. This review will provide relevant scientific researchers with references.

Research progress of MOF-based membrane reactor coupled with AOP technology for organic wastewater treatment

MOF-based catalytic membrane reactor (MCMR), which can simultaneously achieve membrane separation and chemical catalytic degradation in an integrated system, is a cutting-edge technology for effective treatment of organic pollutants in water. The coupling of MCMR and advanced oxidation process (AOP) not only significantly improves the pollutant removal efficiency but also inhibits the membrane pollution through self-cleaning effect, thus improving the stability of MCMR. This paper reviews different MCMR systems combined with photocatalysis, Fenton oxidation, and persulfate activation, elucidates the reaction mechanism, discusses key issues to improve system effectiveness, and suggests future challenges and research directions.

Synthesis of Aluminum-Based Metal-Organic Framework (MOF)-Derived Carbon Nanomaterials and Their Water Adsorption Isotherm

The characteristics of water vapor adsorption depend on the structure, porosity, and functional groups of the material. Metal-organic framework (MOF)-derived carbon (MDC) is a novel material that exhibits a high specific area and tunable pore sizes by exploiting the stable structure and porosity of pure MOF materials. Herein, two types of aluminum-based MOFs were used as precursors to synthesize hydrophobic microporous C-MDC and micro-mesoporous A-MDC via carbonization and activation depending on the type of ligands in the precursors. C-MDC and A-MDC have different pore characteristics and exhibit distinct water adsorption properties. C-MDC with hydrophobic properties and micropores exhibited negligible water adsorption (108.54 mgg-1) at relatively low pressures (P/P0~0.3) but showed a rapid increase in water adsorption ability (475.7 mgg-1) at relative pressures of about 0.6. A comparison with the isotherm model indicated that the results were consistent with the theories, which include site filling at low relative pressure and pore filling at high relative pressure. In particular, the Do-Do model specialized for type 5 showed excellent agreement.

MOF-Derived Co Nanoparticles Catalyst Assisted by F- and N-Doped Carbon Quantum Dots for Oxygen Reduction

The oxygen reduction reaction is crucial in the cathode of fuel cells and metal-air batteries. Consequently, designing robust and durable ORR catalysts is vital to developing metal-air batteries and fuel cells. Metal-organic frameworks feature an adjustable structure, a periodic porosity, and a large specific surface area, endowing their derivative materials with a unique structure. In this study, F and N co-doped on the carbon support surface (Co/FN-C) via the pyrolysis of ZIF-67 as a sacrificial template while using Co/FN-C as the non-noble metal catalysts. The Co/FN-C displays excellent long-term durability and electrochemical catalytic performance in acidic solutions. These performance improvements are achieved because the CQDs alleviate the structural collapse during the pyrolysis of ZIF-67, which increases the active sites in the Co nanoparticles. Moreover, F- and N-doping improves the catalytic activity of the carbon support by providing additional electrons and active sites. Furthermore, F anions are redox-stable ligands that exhibit long-term operational stability. Therefore, the well-dispersed Co NPs on the surface of the Co/FN-C are promising as the non-noble metal catalysts for ORR.

Organic Covalent Interaction-based Frameworks as Emerging Catalysts for Environment and Energy Applications: Current Scenario and Opportunities

The term "covalent organic framework" (COF) refers to a class of porous organic polymeric materials made from organic building blocks that have been covalently bonded. The preplanned and predetermined bonding of the monomer linkers allow them to demonstrate directional flexibility in two- or three-dimensional spaces. COFs are modern materials, and the discovery of new synthesis and linking techniques has made it possible to prepare them with a variety of favorable features and use them in a range of applications. Additionally, they can be post-synthetically altered or transformed into other materials of particular interest to produce compounds with enhanced chemical and physical properties. Because of its tunability in different chemical and physical states, post-synthetic modifications, high stability, functionality, high porosity and ordered geometry, COFs are regarded as one of the most promising materials for catalysis and environmental applications. This study highlights the basic advancements in establishing the stable COFs structures and various post-synthetic modification approaches. Further, the photocatalytic applications, such as organic transformations, degradation of emerging pollutants and removal of heavy metals, production of hydrogen and Conversion of carbon dioxide (CO₂ ) to useful products have also been presented. Finally, the future research directions and probable outcomes have also been summarized, by focusing their promises for specialists in a variety of research fields.

DNA-Programmed Tuning of the Growth and Enzyme-Like Activity of a Bimetallic Nanozyme and Its Biosensing Applications

Nanozymes, which combine the merits of both nanomaterials and natural enzymes, have aroused tremendous attention as new representatives of artificial enzyme mimics. However, it still remains to be a great challenge to rationally engineer the morphologies and surface properties of nanostructures that lead to the desired enzyme-like activities. Here, we report a DNA-programming seed-growth strategy to mediate the growth of platinum nanoparticles (PtNPs) on gold bipyramids (AuBPs) for the synthesis of a bimetallic nanozyme. We find that the preparation of a bimetallic nanozyme is in a sequence-dependent manner, and the encoding of a polyT sequence allows the successful formation of bimetallic nanohybrids with greatly enhanced peroxidase-like activity. We further observe that the morphologies and optical properties of T15-mediated Au/Pt nanostructures (Au/T15/Pt) change over the reaction time, and the nanozymatic activity can be tuned by controlling the experimental conditions. As a concept application, Au/T15/Pt nanozymes are used to establish a simple, sensitive, and selective colorimetric assay for the determination of ascorbic acid (AA), alkaline phosphatase (ALP), and the inhibitor sodium vanadate (Na₃VO₄), demonstrating excellent analytical performance. This work provides a new avenue for the rational design of bimetallic nanozymes for biosensing applications.

Recent advances of metal-organic framework-based and derivative materials in the heterogeneous catalytic removal of volatile organic compounds

Since the environmental hazards of volatile organic compounds (VOCs) are well known, heterogeneous catalysis has become one of the most popular methods to treat VOCs due to its environmental friendliness and simplicity of operation. Although a large number of reports have reviewed the application of catalytic oxidation for the degradation of VOCs, relatively few reports are based on this direction of metal organic frameworks (MOFs) and MOF derivatives. Herein, this paper reviews the recent applications of heterogeneous catalytic technologies in the degradation of VOCs, including photocatalysis, thermal catalysis and other catalytic approaches. The applications of MOFs and their derivatives in VOCs degradation, such as the progress of MOF-derived metal oxides in the treatment of toluene, were highlighted. The mechanisms of VOCs degradation by different catalytic approaches were systematically presented. Finally, we presented the views and directions of VOCs treatment technology development. We hope that this reaction type-oriented review will provide important insights into MOFs and MOF-derived materials for VOCs pollution control.

Bismuth-doped g-C3N4/ZIF-8 heterojunction photocatalysts with enhanced photocatalytic performance under visible light illumination

In this work, g-C₃N₄/ZIF-8 heterojunction photocatalysts were synthesised by the process by which the metal-organic framework ZIF-8 nanoparticles were grown onto the g-C₃N₄ layer in situ. Bismuth element was doped into the as-prepared g-C₃N₄/ZIF-8 material and a new type of Bi@g-C₃N₄/ZIF-8 composite photocatalysts was manufactured, in which the doping element acts in adjusting the bandgap in the photocatalysts. The prepared photocatalysts were characterised by XRD, FESEM, TEM, FTIR, XPS, UV-VIS DRS, photoluminescence and photo-electrochemical experiments. The results show that the ZIF-8 nanoparticles grown in situ were well-formed onto the g-C₃N₄ layer, and bismuth was evenly doped into the gaps of the g-C₃N₄/ZIF-8 framework. The degradation rate of methylene blue by CNZ-1.5(Bi)-12, which was a photocatalyst composed of 12% Bi-doped with g-C₃N₄/ZIF-8 material (the mass ratio of g-C₃N₄: ZIF-8 = 1:1.5), reached 86.6% under visible light irradiation within 60 min. The free radical scavenging experiment and electron spin resonance spectroscopy showed that ∙OH was the main active substance. Bismuth doping into the photocatalytic system promotes the excitation of electrons from the valence band to the conduction band and provides a good channel for the transmission of photogenerated carriers as well. It is achieved that intensive visible light absorption, the enhanced separation efficiency of photogenerated carriers, and excellent thermal stability and high recyclability in the novel composite photocatalyst, owing to the synergistic effect of the introduced bismuth with the heterostructure of g-C₃N₄/ZIF-8. Therefore, the synthesised Bi@g-C₃N₄/ZIF-8 heterojunction photocatalysts may be used as a good photocatalyst for purifying and degrading organic matter in sewage.

Recent advances in determination applications of emerging films based on nanomaterials

Sensitive and facile detection of analytes is crucial in various fields such as agriculture production, food safety, clinical diagnosis and therapy, and environmental monitoring. However, the synergy of complicated sample pretreatment and detection is an urgent challenge. By integrating the inherent porosity, processability and flexibility of films and the diversified merits of nanomaterials, nanomaterial-based films have evolved as preferred candidates to meet the above challenge. Recent years have witnessed the flourishment of films-based detection technologies due to their unique porous structures and integrated physical/chemical merits, which favors the separation/collection and detection of analytes in a rapid, efficient and facile way. In particular, films based on nanomaterials consisting of 0D metal-organic framework particles, 1D nanofibers and carbon nanotubes, and 2D graphene and analogs have drawn increasing attention due to incorporating new properties from nanomaterials. This paper summarizes the progress of the fabrication of emerging films based on nanomaterials and their detection applications in recent five years, focusing on typical electrochemical and optical methods. Some new interesting applications, such as point-of-care testing, wearable devices and detection chips, are proposed and emphasized. This review will provide insights into the integration and processability of films based on nanomaterials, thus stimulate further contributions towards films based on nanomaterials for high-performance analytical-chemistry-related applications.

Titanium-Porphyrin Metal-Organic Frameworks as Visible-Light-Driven Catalysts for Highly Efficient Sonophotocatalytic Reduction of Cr(VI)

In this work, we synthesized and characterized four titanium-porphyrin metal-organic frameworks (MOFs) [DGIST-1(M), M = Co(II), Fe(III), Zn(II), and H₂] and used them as visible-light-driven catalysts for sonophotocatalytic Cr(VI) reduction. DGIST-1(M) exhibited open-framework, broad light absorption stemmed from ligand and sensitive photocurrent responses owing to the integration of one-dimensional Ti-oxo chains and 4-connected conjugated TCPP ligand (TCPP = tetrakis(4-carboxyphenyl)-porphyrin). DGIST-1(M) presented efficient reduction of Cr(VI) to Cr(III) in aqueous solution when used as sonophotocatalytic catalysts. The average reduction rates upon Cr(VI) were 0.920, 0.476, 0.377, and 0.194 mg·L^-1·min^-1 for DGIST-1(H₂), DGIST-1(Zn), DGIST-1(Co), and DGIST-1(Fe), which are 1.15-2.45 times higher than those in photocatalysis. Sonophotocatalytic experiments and electron paramagnetic resonance measurement proved that Ti-oxo chain units and porphyrin ligand in the structures of DGIST-1(M) existed as catalytic active centers for sonophotocatalytic reduction of Cr(VI). Photoluminescence and UV absorption spectra revealed that the unity of photocatalysis and sonochemistry strengthened the migration of photogenerated electrons from DGIST-1(M) to Cr(VI), which improved the activities of catalysts. This study suggested that the association of titanium-porphyrin MOFs and sonophotocatalytic technology is an impactful program for enhancing MOF-based photocatalytic systems.

Zn-Metal-Organic Framework Derived Ordered Mesoporous Carbon-Based Nanostructure for High-Performance and Universal Multivalent Metal Ion Storage

Metal-organic framework (MOF) derivatives promise great potential in energy storage and conversion because of their excellent tunability in both the active metal sites, organic links, and the overall structures down to atomic and up to mesoscale. Nevertheless, a big challenge is to precisely control and thoroughly understand the actual MOF-to-derivative conversion process to realize the template-free synthesis of the MOF-derived ordered mesoporous materials. Here, a class of ordered mesoporous N-doped carbon nanoflakes is presented with slit-shaped pores synthesized by one-step pyrolysis of Zn₁ Cu_x -MOF, where the Cu doping plays a critically important direction-inducing function on the dissociation of organic ligands during the pyrolysis. Benefiting from the uniquely ordered mesoporous structure and large specific surface area (910 m² g^-1 ), the Zn₁ Cu_x -MOF-derived ordered mesoporous carbon nanoflakes present outstanding electrochemical storage performance for multivalent metal ions, such as Mg²⁺ , Ca²⁺ , Co²⁺ , Ni²⁺ , Al³⁺ , and Zn²⁺ , demonstrating the universal nature of the slit-shaped pores in enabling the multivalent metal ions for energy storage. Moreover, the assembled flexible Zn-ion hybrid supercapacitor (ZHSC) delivers a high specific capacity of 134 mAh g^-1 at 0.5 A g^-1 , excellent cycling and mechanical stability, showing great application potential in the new generation energy storage devices.

A Fe3O4 nanospheres/carbon core–shell structure for effective removal of pollutants from water

The treatment of wastewater by adsorption is a good alternative technique and attracts extensive attention worldwide due to its versatility, scalability, and low operational costs. In this work, a Fe3O4 nanospheres/carbon core–shell structure is fabricated by combination of a template method and calcination. The morphology and crystal structure of the synthesized composite are characterized by transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectrometer, and from nitrogen adsorption–desorption isotherms, confirming that the carbon layer with a porous structure is successfully loaded onto the surface of the face-centered cubic Fe3O4 nanospheres to form a core–shell structure. The adsorption performance of the Fe3O4 nanospheres/carbon core–shell structure is investigated by studying the effects of the initial pH value of the solution, the contact time, the initial concentration of the pollutants, the adsorption temperature, and the amount of adsorbent. The Fe3O4 nanospheres/carbon core–shell structure effectively removes heavy metal Chromium(VI) and a reactive light yellow dye. The results of batch experiments show that the removal efficiencies of heavy metal Chromium(VI) and the reactive light yellow dye are close to 100% under optimized conditions. The good adsorption performance of the Fe3O4 nanospheres/carbon core–shell structure toward various types of pollutants suggests a potential application in wastewater treatment.

Photocatalytic reduction of low-concentration CO2 by metal-organic frameworks

Direct conversion of diluted CO₂ to value-added chemical stocks and fuels with solar energy is an energy-saving approach to relieve global warming and realize a carbon-neutral cycle. The exploration of catalysts with both efficient CO₂ adsorption and reduction ability is significant to achieving this goal. Metal-organic frameworks (MOFs) are emerging in the field of low-concentration CO₂ reduction due to their highly tunable structure, high porosity, abundant active sites and excellent CO₂ adsorption capacity. This highlight outlines the advantages of MOFs for low-pressure CO₂ adsorption and the strategies to improve the photocatalytic performance of MOF materials at low CO₂ concentrations, including the functionalization of organic ligands, regulation of metal nodes and preparation of MOF composites or derivatives. This paper aims to provide possible avenues for the rational design and development of catalysts with the ability to reduce low-concentration CO₂ efficiently for practical applications.

Recent progress of functional metal-organic framework materials for water treatment using sulfate radicals

Human health is being threatened by the ever-increasing water pollution. Sulfate radical (SO₄^•-)-based advanced oxidation processes (SR-AOPs) are rapidly being developed and gaining considerable attention due to their high oxidation potential and selectivity as a way to purify water by degrading organic contaminants in it. Among the catalytic materials that can activate the precursor to generate SO₄^•-, metal-organic frameworks (MOFs) are the most promising heterogeneous catalytic material in SR-AOPs because of their various structure possibilities, large surface area, ordered porous structure, and regular activation sites. Herein, an in-depth overview of MOFs and their derivatives for water purification with SR-AOPs is provided. The latest studies on pristine MOFs, MOF composites, and MOF derivatives (metal oxides, metal-carbon hybrids, and carbon materials) are summarized. The mechanisms of decomposition of pollutants in water via radical and non-radical pathways are also discussed. This review suggests future research directions for water purification through MOF-based SR-AOP.

Metal-organic frameworks as a therapeutic strategy for lung diseases

Lung diseases remain a global burden today. Lower respiratory tract infections alone cause more than 3 million deaths worldwide each year and are on the rise every year. In particular, with coronavirus disease raging worldwide since 2019, we urgently require a treatment for lung disease. Metal organic frameworks (MOFs) have a broad application prospect in the biomedical field due to their remarkable properties. The unique properties of MOFs allow them to be applied as delivery materials for different drugs; diversified structural design endows MOFs with diverse functions; and they can be designed as various MOF-drug synergistic systems. This review concentrates on the synthesis design and applications of MOF based drugs against lung diseases, and discusses the possibility of preparing MOF-based inhalable formulations. Finally, we discuss the chances and challenges of using MOFs for targeting lung diseases in clinical practice.

Nanomaterials for microplastic remediation from aquatic environment: Why nano matters?

The contamination of microplastics in aquatic environment is regarded as a serious threat to ecosystem especially to aquatic environment. Microplastic pollution associated problems including their bioaccumulation and ecological risks have become a major concern of the public and scientific community. The removal of microplastics from their discharge points is an effective way to mitigate the adverse effects of microplastic pollution, hence has been the central of the research in this realm. Presently, most of the commonly used water or wastewater treatment technologies are capable of removing microplastic to certain extent, although they are not intentionally installed for this reason. Nevertheless, recognizing the adverse effects posed by microplastic pollution, more efforts are still desired to enhance the current microplastic removal technologies. With their structural multifunctionalities and flexibility, nanomaterials have been increasingly used for water and wastewater treatment to improve the treatment efficiency. Particularly, the unique features of nanomaterials have been harnessed in synthesizing high performance adsorbent and photocatalyst for microplastic removal from aqueous environment. This review looks into the potentials of nanomaterials in offering constructive solutions to resolve the bottlenecks and enhance the efficiencies of the existing materials used for microplastic removal. The current efforts and research direction of which studies can dedicate to improve microplastic removal from water environment with the augmentation of nanomaterial-enabled strategies are discussed. The progresses made to date have witnessed the benefits of harnessing the structural and dimensional advantages of nanomaterials to enhance the efficiency of existing microplastic treatment processes to achieve a more sustainable microplastic cleanup.

Does political risk drive environmental degradation in BRICS countries? Evidence from method of moments quantile regression

As a contribution to the political risk-environmental degradation literature, this study examines whether political risk drives environmental degradation in a multivariate framework. To achieve our study objective, we employed the method of moments quantile regression (MMQR) approach to analyze the effect of renewable energy use, economic growth, political risk, and globalization on quantiles of carbon emissions. The study utilized dataset stretching between 1990 and 2018 to investigate this interrelationship in the BRICS nations. The results generated from the MMQR mimic those of the three heterogeneous linear panel estimation techniques conducted (for robustness check), in terms of coefficient sign, magnitude, and significance. Using the MMQR technique, empirical results show that across quantiles (0.1-0.90), political risk, economic growth, and globalization positively affects environmental degradation. Renewable energy consumption, on the other hand, curb environmental degradation across all quantiles (0.10-0.90). Furthermore, the outcomes of the FMOLS, DOLS, and FEOLS corroborated the MMQR outcomes. In addition, the outcomes of the Dumitrescu-Hurlin panel causality revealed that renewable energy use, political risk, economic growth, and globalization can significantly predict CO₂ emissions in the BRICS nations. The findings offer intuition for policymakers to lessen CO₂ emissions in BRICS nations via diversification and clean energy technologies such as carbon capture and storage.

Recent Advances in the Application and Mechanism of Carbon Dots/Metal-Organic Frameworks Hybrids in Photocatalysis and the Detection of Environmental Pollutants

Metal-organic frameworks (MOFs) are a class of crystalline porous materials with simple synthesis conditions, large specific surface area, structural diversity, and a wide range of interesting properties. The integration of MOFs with other materials can provide new multifunctional composites that exhibit both component properties and new characteristics. In recent years, the integration of carbon dots (CDs) into MOFs to form composites has shown improved optical properties and fascinating new characteristics. This review focuses on the design and synthesis strategies of CDs@MOFs composites (including pore-confined synthesis, in situ encapsulation, post-synthesis modification and impregnation method) and their recent research progress in photocatalysis and detection of environmental pollutants. Both the achievements and problems are evaluated and proposed, and the opportunities and challenges of CDs@MOF composite are discussed.

One-Step construction of Polyimide/NH2-UiO-66 heterojunction for enhanced photocatalytic degradation of sulfonamides

Photocatalysis treatment is a promising technology to eliminate water pollutants. Herein, we constructed polyimide/NH₂-UiO-66 composites (PUs) through a facile one-step solvothermal method for the photocatalytic degradation of sulfonamides. The optimized photocatalyst PU1.5 was superior to the photocatalysts prepared through multi-step methods due to the more exposed (001) facets of polyimide and the better distribution of small NH₂-UiO-66 particles. PU1.5 showed the highest photocatalytic activity, which was 9.5 and 92.0 times higher than that of polyimide and NH₂-UiO-66. Such improvement was attributed to the improved carrier separation efficiency resulted from direct Z-scheme heterojunction. The probable degradation pathway of sulfathiazole was proposed by the LC-MS/MS and Density Functional Theory (DFT) calculation. Furthermore, the reduced toxicity and the little antibacterial activity of intermediates was investigated by the Quantitative Structure-Activity Relationship (QSAR) analysis and the residual antibiotic activity experiment. The study might provide a new strategy for designing composite photocatalyst to achieve efficient removal of pollutants.

Derivatives of metal-organic frameworks for heterogeneous Fenton-like processes: From preparation to performance and mechanisms in wastewater purification - A mini review

Organic pollution is an ever-growing issue in aquatic environment, Fenton-like processes have gained widespread acceptance due to their high oxidative potential and environmental compatibility. Derivatives of metal-organic frameworks (MOFs) are emerging heterogeneous Fenton-like catalysts, which have advantages of large surface area, diversity of structures, and abundant active sites. This work focuses on the recent advances in MOFs derivatives including metal compounds and metal incorporated carbons for Fenton-like processes. First, preparation strategies, structures and compositions are introduced. And then, the removal of organic pollutant in Fenton, electro-Fenton, and photo-Fenton process catalyzed by MOFs derivative is summarized, respectively. The contents particularly devote efforts to build connections among preparation, structures, compositions, and performance. Furthermore, the mechanisms of improving performance are discussed in detail. Finally, the perspectives of MOFs derivatives toward Fenton-like applications are proposed.

Advanced Metal–Organic Frameworks-Based Catalysts in Electrochemical Sensors

Developing efficient catalysts is vital for the application of electrochemical sensors. Metal–organic frameworks (MOFs), with high porosity, large specific surface area, good conductivity, and biocompatibility, have been widely used in catalysis, adsorption, separation, and energy storage applications. In this invited review, the recent advances of a novel MOF-based catalysts in electrochemical sensors are summarized. Based on the structure–activity–performance relationship of MOF-based catalysts, their mechanism as electrochemical sensor, including metal cations, synthetic ligands, and structure, are introduced. Then, the MOF-based composites are successively divided into metal-based, carbon-based, and other MOF-based composites. Furthermore, their application in environmental monitoring, food safety control, and clinical diagnosis is discussed. The perspective and challenges for advanced MOF-based composites are proposed at the end of this contribution.

Selenium removal from water using adsorbents: A critical review

Selenium (Se) has become an increasingly serious water contamination concern worldwide. It is an essential micronutrient for humans and animals, however, can be extremely toxic if taken in excess. Sorption can be an effective treatment for Se removal from a wide range of water matrices. However, despite the synthesis and application of numerous adsorbents for remediation of aqueous Se, there has been no comprehensive review of the sorption capacities of various natural and synthesized sorbents. Herein, literature from 2010 to 2021 considering Se remediation using 112 adsorbents has been critically reviewed and presented in several comprehensive tables including: clay minerals and waste materials (presented in Table 1); zero-valent iron, iron oxides, and binary iron-based adsorbents (Table 2); other metals-based adsorbents (Table 3); carbon-based adsorbents (Table 4); and other adsorbents (Table 5). Each of these tables, and their relevant sections, summarizes preparation/modification methods, sorption capacities of various Se adsorbents, and proposed model/mechanisms of adsorption. Furthermore, future perspectives have been provided to assist in filling noted research gaps for the development of efficient Se adsorbents for real-world applications. This review will help in preliminary screening of various sorbent media to set up Se treatment technologies for a variety of end-users worldwide.

Zirconium-Based Metal Organic Frameworks for the Capture of Carbon Dioxide and Ethanol Vapour. A Comparative Study

This paper reports on the comparison of three zirconium-based metal organic frameworks (MOFs) for the capture of carbon dioxide and ethanol vapour at ambient conditions. In terms of efficiency, two parameters were evaluated by experimental and modeling means, namely the nature of the ligands and the size of the cavities. We demonstrated that amongst three Zr-based MOFs, MIP-202 has the highest affinity for CO2 (-50 kJ·mol-1 at low coverage against around -20 kJ·mol-1 for MOF-801 and Muc Zr MOF), which could be related to the presence of amino functions borne by its aspartic acid ligands as well as the presence of extra-framework anions. On the other side, regardless of the ligand size, these three materials were able to adsorb similar amounts of carbon dioxide at 1 atm (between 2 and 2.5 µmol·m-2 at 298 K). These experimental findings were consistent with modeling studies, despite chemisorption effects, which could not be taken into consideration by classical Monte Carlo simulations. Ethanol adsorption confirmed these results, higher enthalpies being found at low coverage for the three materials because of stronger van der Waals interactions. Two distinct sorption processes were proposed in the case of MIP-202 to explain the shape of the enthalpic profiles.

A review on the preparation, microstructure, and photocatalytic performance of Bi2O3 in polymorphs

In recent years, the semiconductor bismuth oxide (Bi₂O₃) has attracted increasing attention as a potential visible-light-driven photocatalyst due to its simple composition, relatively narrow bandgap (2.2-2.8 eV), and high oxidation ability with deep valence band levels. Owing to the symmetry of its unit cell, Bi₂O₃ exists in more than one crystal form and exhibits phase-dependent photocatalytic properties. However, the phase-selective synthesis of Bi₂O₃ is a complex process, and its phase transformation usually occurs in a wide temperature range. Therefore, the development of Bi₂O₃ phases with a controllable microstructure and good photocatalytic properties is a great challenge. Hundreds of articles have been reported on the phase-selective synthesis and photocatalytic performance of Bi₂O₃. However, an interacting and critical review has rarely been reported, and thus it is essential to fill the gap in the literature. In this review, the phase-dependent photocatalytic performance of Bi₂O₃ is presented in detail. The phase-selective synthesis and temperature-dependent phase stability of highly active Bi₂O₃ are explored. The phase junction in Bi₂O₃ is reviewed, and the future perspective with an outlook on contemporary challenges is provided finally.

Metal-organic frameworks as superior porous adsorbents for radionuclide sequestration: Current status and perspectives

Efficient separation of hazardous radionuclides from radioactive waste remains a challenge to the global acceptance of nuclear power due to complex nature of the waste, high radiotoxicities and presence of large number of interfering elements. Sorption of radioactive elements from liquid phase, gas phase or their solid particulates on various synthetic organic, inorganic or biological sorbents is looked as one of the options for their remediation. In this context, highly porous materials, termed as metal-organic frameworks (MOFs), have shown promise for efficient capturing of various types of radioactive elements. Major advantages that have been advocated for the application of MOFs in radionuclide sorption are their excellent chemical stability, and their large surface area due to abundant functional groups, and porosity. In this review, recent developments on the application of MOFs for radionuclide sequestration are briefly discussed. Focus has been devoted to address the separation of few crucial radioactive elements such as Th, U, Tc, Re, Se, Sr and Cs from aqueous solutions, which are important for liquid radioactive waste management. Apart from these radioactive metal ions, removal of radionuclide bearing gases such as I₂, Xe, and Kr are also discussed. Aspects related to the interaction of MOFs with the radionuclides are also discussed. Finally, a perspective for comprehensive investigation of MOFs for their applications in radioactive waste management has been outlined.

Recent Progress in Metal-Organic Framework-Derived Nanostructures in the Removal of Volatile Organic Compounds

Air is the most crucial and life-supporting input from nature to the living beings of the planet. The composition and quality of air significantly affects human health, either directly or indirectly. The presence of some industrially released gases, small particles of anthropogenic origin, and the deviation from the normal composition of air from the natural condition causes air pollution. Volatile organic compounds (VOCs) are common contaminants found as indoor as well as outdoor pollutants. Such pollutants represent acute or chronic health hazards to the human physiological system. In the environment, such polluted gases may cause chemical or photochemical smog, leading to detrimental effects such as acid rain, global warming, and environmental pollution through different routes. Ultimately, this will propagate into the food web and affect the ecosystem. In this context, the efficient removal of volatile organic compounds (VOCs) from the environment remains a major threat globally, yet satisfactory strategies and auxiliary materials are far from being in place. Metal–organic frameworks (MOFs) are known as an advanced class of porous coordination polymers, a smart material constructed from the covalently bonded and highly ordered arrangements of metal nodes and polyfunctional organic linkers with an organic–inorganic hybrid nature, high porosities and surface areas, abundant metal/organic species, large pore volumes, and elegant tunability of structures and compositions, making them ideal candidates for the removal of unwanted VOCs from air. This review summarizes the fundamentals of MOFs and VOCs with recent research progress on MOF-derived nanostructures/porous materials and their composites for the efficient removal of VOCs in the air, the remaining challenges, and some prospective for future efforts.