Metal-organic Framework Composites Research Articles

A monolithic gold nanoparticle@metal-organic framework composite as CO2 photoreduction catalyst

The application of metal-organic frameworks (MOFs), especially MOF composites, has been hindered by a lack of method to process powders into useable forms. To address this challenge, we report here a low temperature synthesis method that enables direct formation of a densified monolithic MOF composite, i.e. Au@ZIF-67. The monolithic composite contains Au nanoparticles (Au NPs) that are well-dispersed and encapsulated within ZIF-67 particles. It exhibits high surface area, bulk density, and mechanical robustness as observed in monolithic ZIF-67, while retaining the localized surface plasmonic resonance (LSPR) characteristic of Au NPs. Benefiting from this unique combination, the monolithic Au@ZIF-67 samples display an enhanced CO2 photoreduction performance under visible light—with the best-performing Au@ZIF-67 sample showing a volumetric CO production rate 1.5 and 3 times higher compared to the pristine monolithic ZIF-67 and ZIF-67 powder, respectively.

Composites Filled with Metal Organic Frameworks and Their Derivatives: Recent Developments in Flame Retardants

Polymer matrix is vulnerable to fire hazards and needs to add flame retardants to enhance its performance and make its application scenarios more extensive. At this stage, it is more necessary to add multiple flame-retardant elements and build a multi-component synergistic system. Metal organic frameworks (MOFs) have been studied for nearly three decades since their introduction. MOFs are known for their structural advantages but have only been applied to flame-retardant polymers for a relatively short period of time. In this paper, we review the development of MOFs utilized as flame retardants and analyze the flame-retardant mechanisms in the gas phase and condensed phase from the original MOF materials, modified MOF composites, and MOF-derived composites as flame retardants, respectively. The effects of carbon-based materials, phosphorus-based materials, nitrogen-based materials, and biomass on the flame-retardant properties of polymers are discussed in the context of MOFs. The construction of MOF multi-structured flame retardants is also introduced, and a variety of MOF-based flame retardants with different morphologies are shown to broaden the ideas for subsequent research.

Smart metal-organic framework (MOF) composites and their applications in environmental remediation

The applications of stimuli-responsive metal-organic frameworks (MOFs) during environmental remediation are discussed in detail in this paper. MOFs are highly porous materials with generally high adsorption capacity of environmental pollutants. The incorporation of stimuli-responsive moieties in their structures confer them with additional properties such as being easily recovered and recyclability. Consequently, there is an increase in the use of stimuli-responsive MOFs during environmental remediation. Some researchers have successfully incorporated photoactive species into the structures of MOFs resulting in the formation of light-responsive composites. The presence of thermo-responsive polymeric units in the structure of an MOF make it to have physicochemical properties that are sensitive to temperature changes. The recovery of MOFs composites can be facilitated by the incorporation of magnetic nanoparticles into their structures. This review explores the utilisation of thermo-responsive MOFs, light-responsive MOFs and magnetic responsive MOFs during environmental remediation. In addition, challenges associated with the use of smart MOFs during the remediation of polluted environments are discussed in detail in this review as well as their future prospects. • Smart MOFs are efficient adsorbents for environmental remediation • Their physicochemical properties are responsive to stimuli • Light, temperature, and magnetic stimulations are usually involved in smart MOFs • Adsorption/desorption processes in smart MOFs are triggered by changes in stimuli • Smart MOF=based membranes have stimuli-regulated pore sizes

Surface Modification of Magnetic ZIF-90 Nanoparticles Improves the Microenvironment of Immobilized Lipase and Its Application in Esterification.

Interactions of enzymes with supports significantly affect the activity and stability of immobilized enzymes. Herein, amino-functionalized ionic liquid (IL)-grafted magnetic zeolitic imidazolate framework-90 (MZIF-90) was prepared and used to immobilize porcine pancreatic lipase (PPL). The nanocomposites were fully characterized; meanwhile, the interactions between ILs and ZIF-90 were calculated based on density functional theory. The prepared biocatalyst (PPL-ILs/MZIF-90) had a lipase loading of 178.3 mg/g and hydrolysis activity up to 287.5 U/g. When the biocatalyst was used to synthesize isoamyl acetate, the reaction media, molar ratio of alcohol/acid, temperature, and reaction time were optimized. Under the optimized reaction conditions (in hexane, alcohol/acid = 3:1, under 45 °C, reacted for 9 h), the ester yield reached 85.5%. The results of the stability test showed that PPL-ILs/MZIF-90 retained 88.7% of the initial activity after storing for 35 days and 92.5% of the initial activity after reusing for seven cycles for synthesizing isoamyl acetate. Moreover, the secondary structure analysis showed that the synthesized supports protected the active conformation of immobilized lipase, which lead to the enhanced catalytic performance. Additionally, the biocatalyst can be easily separated with a magnet, which facilitated the reusability. This study provides insights regarding the application of metal organic framework composites in the field of enzyme catalysis.

Engineering Single-Atom Sites into Pore-Confined Nanospaces of Porphyrinic Metal-Organic Frameworks for the Highly Efficient Photocatalytic Hydrogen Evolution Reaction.

As a type of heterogeneous catalyst expected for the maximum atom efficiency, a series of single-atom catalysts (SACs) containing spatially isolated metal single atoms (M-SAs) have been successfully prepared by confining M-SAs in the pore-nanospaces of porphyrinic metal-organic frameworks (MOFs). The prepared MOF composites of M-SAs@Pd-PCN-222-NH2 (M = Pt, Ir, Au, and Ru) display exceptionally high and persistent efficiency in the photocatalytic hydrogen evolution reaction with a turnover number (TON) of up to 21713 in 32 h and a beginning/lasting turnover frequency (TOF) larger than 1200/600 h-1 based on M-SAs under visible light irradiation (λ ≥ 420 nm). The photo-/electrochemical property studies and density functional theory calculations disclose that the close proximity of the catalytically active Pt-SAs to the Pd-porphyrin photosensitizers with the confinement and stabilization effect by chemical binding could accelerate electron-hole separation and charge transfer in pore-nanospaces, thus promoting the catalytic H2 evolution reaction with lasting effectiveness.

N-Heterocyclic Carbene Silver Complex Modified Polyacrylonitrile Fiber/MIL-101(Cr) Composite as Efficient Chiral Catalyst for Three-Component Coupling Reaction.

Complex asymmetric synthesis can be realized by the chiral induction of amino acids in nature. It is of great significance to design a new biomimetic catalytic system for asymmetric synthesis. In this context, we report the preparation and characterization of the composite of polyacrylonitrile fiber (PANF) and metal-organic framework to catalyze the chiral synthesis of propargylamines. A confined microenvironment is established with N-heterocyclic carbene (NHC) silver complex-supported PANF and D-proline-encapsulated MIL-101(Cr). This novel supported catalyst demonstrated high activity in addition to excellent stereoselectivity in the three-component reaction between alkynes, aldehydes, and amines (A3). The regeneration can be realized by adsorption of D-proline again when the stereoselectivity decreases after recycle uses. By regulating the confined microenvironment on the composite, the activity and selectivity of the catalytic system are improved with turnover numbers of up to 2800 and 98% ee. The biomimetic catalytic system to A3 coupling reaction is systematically studied, and the synergistic catalytic mechanism between NHC-Ag and D-proline in the confined microenvironment is revealed.

Metal-Organic Framework-Based Composites for the Detection and Monitoring of Pharmaceutical Compounds in Biological and Environmental Matrices.

The production of synthetic drugs is considered a huge milestone in the healthcare sector, transforming the overall health, aging, and lifestyle of the general population. Due to the surge in production and consumption, pharmaceutical drugs have emerged as potential environmental pollutants that are toxic with low biodegradability. Traditional chromatographic techniques in practice are time-consuming and expensive, despite good precision. Alternatively, electroanalytical techniques are recently identified to be selective, rapid, sensitive, and easier for drug detection. Metal-organic frameworks (MOFs) are known for their intrinsic porous nature, high surface area, and diversity in structural design that provides credible drug-sensing capacities. Long-term reusability and maintaining chemo-structural integrity are major challenges that are countered by ligand-metal combinations, optimization of synthetic conditions, functionalization, and direct MOFs growth over the electrode surface. Moreover, chemical instability and lower conductivities limited the mass commercialization of MOF-based materials in the fields of biosensing, imaging, drug release, therapeutics, and clinical diagnostics. This review is dedicated to analyzing the various combinations of MOFs used for electrochemical detection of pharmaceutical drugs, comprising antibiotics, analgesics, anticancer, antituberculosis, and veterinary drugs. Furthermore, the relationship between the composition, morphology and structural properties of MOFs with their detection capabilities for each drug species is elucidated.

Advances in Titanium Carbide (Ti3C2T x ) MXenes and Their Metal-Organic Framework (MOF)-Based Nanotextures for Solar Energy Applications: A Review.

Introducing new materials with low cost and superior solar harvesting efficiency requires urgent attention to solve energy and environmental challenges. Titanium carbide (Ti3C2T x ) MXene, a 2D layered material, is a promising solution to solve the issues of existing materials due to their promising conductivity with low cost to function as a cocatalyst/support. On the other hand, metal-organic frameworks (MOFs) are emerging materials due to their high surface area and semiconducting characteristics. Therefore, coupling them would be promising to form composites with higher solar harvesting efficiency. Thus, the main objective of this work to disclose recent development in Ti3C2T x -based MOF nanocomposites for energy conversion applications to produce renewable fuels. MOFs can generate photoinduced electron/hole pairs, followed by transfer of electrons to MXenes through Schottky junctions for photoredox reactions. Currently, the principles, fundamentals, and mechanism of photocatalytic systems with construction of Schottky junctions are critically discussed. Then the basics of MOFs are discussed thoroughly in terms of their physical properties, morphologies, optical properties, and derivatives. The synthesis of Ti3C2T x MXenes and their composites with the formation of surface functionals is systematically illustrated. Next, critical discussions are conducted on design considerations and strategies to engineer the morphology of Ti3C2T x MXenes and MOFs. The interfacial/heterojunction modification strategies of Ti3C2T x MXenes and MOFs are then deeply discussed to understand the roles of both materials. Following that, the applications of MXene-mediated MOF nanotextures in view of CO2 reduction and water splitting for solar fuel production are critically analyzed. Finally, the challenges and a perspective toward the future research of MXene-based MOF composites are disclosed.

Facet Engineering of a Metal–Organic Framework Support Modulates the Microenvironment of Palladium Nanoparticles for Selective Hydrogenation

AbstractThe exposed facets of supported catalysts play a crucial role in catalysis; however, they are usually ignored and related studies remain rare. Herein, we have fabricated a series of sandwich‐structured metal–organic framework composites, denoted ZIF‐8X@Pd@ZIF‐8 (x represents the morphology of ZIF‐8 core, i.e., ZIF‐8C exposing (100) facet, ZIF‐8RD exposing (110) facet, and ZIF‐8TRD exposing mixed (100) and (110) facets), featuring Pd nanoparticles deposited on the specific crystal facets of ZIF‐8 core, for hydrogenation of p‐chloronitrobenzene. The Pd electronic state is tailored by the ZIF‐8 core, where more electron‐deficient Pd is found in ZIF‐8C@Pd@ZIF‐8 than that in ZIF‐8RD@Pd@ZIF‐8, leading to discriminative adsorption of the −NO2 and −Cl groups of p‐chloronitrobenzene. Consequently, ZIF‐8C@Pd@ZIF‐8 exhibits excellent activity (97.6 %) and selectivity (98.1 %) to p‐chloroaniline. This work highlights crystal facet engineering of supports to modulate the microenvironment and electronic state of supported metal nanoparticles, offering a promising avenue to enhanced catalysis.

Facet Engineering of a Metal-Organic Framework Support Modulates the Microenvironment of Palladium Nanoparticles for Selective Hydrogenation.

The exposed facets of supported catalysts play a crucial role in catalysis; however, they are usually ignored and related studies remain rare. Herein, we have fabricated a series of sandwich-structured metal-organic framework composites, denoted ZIF-8X @Pd@ZIF-8 (x represents the morphology of ZIF-8 core, i.e., ZIF-8C exposing (100) facet, ZIF-8RD exposing (110) facet, and ZIF-8TRD exposing mixed (100) and (110) facets), featuring Pd nanoparticles deposited on the specific crystal facets of ZIF-8 core, for hydrogenation of p-chloronitrobenzene. The Pd electronic state is tailored by the ZIF-8 core, where more electron-deficient Pd is found in ZIF-8C @Pd@ZIF-8 than that in ZIF-8RD @Pd@ZIF-8, leading to discriminative adsorption of the -NO2 and -Cl groups of p-chloronitrobenzene. Consequently, ZIF-8C @Pd@ZIF-8 exhibits excellent activity (97.6 %) and selectivity (98.1 %) to p-chloroaniline. This work highlights crystal facet engineering of supports to modulate the microenvironment and electronic state of supported metal nanoparticles, offering a promising avenue to enhanced catalysis.

Application of a magnetic solid-phase extraction method using a novel magnetic metal organic framework nanocomposite for extraction of malathion and diazinon pesticides from environmental water samples

Herein, a magnetic solid-phase extraction (MSPE) method using a synthesized magnetic metal-organic framework composite (Cu-MOF@Fe3O4@SiO2) was applied for the extraction of two well-known organophosphorus pesticides (Malathion and Diazinon) in several environmental water samples. After the extraction, the mentioned target analytes were measured by HPLC-UV. Under the optimal conditions obtained, acceptable linearity was observed within the concentration ranges of 10.0–500.0, and 5.0–500.0 μg/L for malathion and diazinon, respectively. The respective limits of quantification (LOQs) were determined to be 10.0 and 5.0 μg/L for malathion and diazinon. Besides, the MSPE method was successfully implemented to determine the two targets in tap water, surface water, well water, and treated waste water samples with the recoveries varying from 84.0 to 105.5 % (RSDs = 3.8–9.6 %). The obtained results indicated that the combined MOF-based MSPE/HPLC-UV method is of several valuable analytical features, such as high sensitivity, good precision, and the ease of operation and it is practically effective for the extraction and determination of organophosphorus pesticides in various water samples.

Flexible film and thermoelectric device of single-walled carbon nanotube@conductive metal-organic framework composite

Conducting metal-organic frameworks (MOFs) hold a great potential for many electronic applications because of their unique chemical and physical properties. Thermoelectric (TE) conversation based on conductive MOFs is the cutting-edge frontiers and remains great challenges, such as low electrical conductivity, rigidity, and difficulty to process. Here, a free-standing flexible film of the composite, where covalent bond grafting exists between single-walled carbon nanotubes (SWCNTs) and porous MOF (SWCNT@Ni-1,2,5,6,9,10-triphenylenehexathiol (THT)), is prepared by a convenient vacuum filtration method. The as-fabricated SWCNT@Ni-THT composite films exhibit good flexibility and p-type TE characteristics. An optimized power factor and a maximum figure of merit are ∼98.1 μW m-1/K2 and ∼0.037, respectively, for the composite film with 4 wt% SWCNT loading at 300 K. Furthermore, a flexible TE device connected by four rectangular films in series can generate an open-circuit voltage (VOC) of ∼10.02 μV and the maximum power (Pmax) of ∼1.59 μW at a temperature difference of 60 K. This work provides a novel way to prepare high-performance flexible films of MOF-based TE composites and demonstrates their potential applications in wearable electronics.

Modular Construction of an MIL-101(Fe)@MIL-100(Fe) Dual-Compartment Nanoreactor and Its Boosted Photocatalytic Activity toward Tetracycline.

Iron-based metal-organic frameworks (MOFs) have aroused extensive concern as prospective photocatalysts for antibiotic (e.g., tetracycline, TC) degradation. However, efficiencies of single and simple Fe-based MOFs still undergo restricted light absorption and weak charge separation. Assembly of different iron-based MOF building blocks into a hybrid MOF@MOF heterostructure reactor could be an encouraging strategy for the effective capture of antibiotics from the aqueous phase. This paper reports a new-style MIL-101(Fe)@MIL-100(Fe) photocatalyst, which was groundbreakingly constructed to realize a double win for boosting the performances of adsorption and photocatalysis. The optical response range, surface open sites, and charge separation efficiency of MIL-101(Fe)@MIL-100(Fe) can be regulated through accurate design and alteration. Attributed to the synergistic effects of double iron-based MOFs, MIL-101(Fe)@MIL-100(Fe) exhibits an excellent photocatalytic activity toward TC degradability compared to MIL-101(Fe) and MIL-100(Fe), which is even superior to those reported previously in the literature. Furthermore, the main active species of •O2- and h+ were proved through trapping tests of the photocatalytic process. Additionally, MIL-101(Fe)@MIL-100(Fe) possesses remarkable stability, maintaining more than 90% initial photocatalytic activity after the fifth cycle. In brief, MIL-101(Fe)@MIL-100(Fe) was highly efficient for TC degradation. Our work offers a new strategy for visible-light photodegradation of TC by exploring the double Fe-based MOF composite.

Sustainable Fe-MOF@carbon nanocomposite electrode for supercapacitor

The development of next-generation supercapacitors requires efficient integration of conductive and charge storage framework with safer and sustainable production methods. Herein, a simple one-pot synthesis was used to synthesize Iron based metal-organic framework and carbon composite (Fe-MOF@AC) electrode. The fabricated electrode delivered a high-power storage capacity due to low interfacial resistance between the working electrode and electrolyte. The activated carbon (AC) was obtained from recycled polystyrene, with the aim of reducing plastic pollution and to foster cleaner, sustainable environment. Plastic with insulating property was transformed to highly conductive graphitized carbon, which act as electron reservoirs for pristine Fe-MOF electrodes. Importantly, we show that the increased carbon content up to saturation limit, enables redox to pseudocapacitive behavior with satisfactory capacitive and cyclic stability despite a minimal drop in internal resistance. The MOF electrode composited with 70 mg of AC, Fe-MOF@AC70 retained ∼82% of its initial capacity (628.5 F g−1) after 10,000 cycles. Both surface-controlled and diffusion-controlled charge transfer mechanism contribute to the charge storage, with diffusion-controlled being more prevalent in Fe-MOF@AC70. The calculated energy and power density were 16.24 Wh kg−1 and 897.5 W kg−1, respectively for the fabricated Fe-MOF@AC70/carbon cloth electrode.

Preparation and Characterization of Magnetic Metal-Organic Frameworks Functionalized by Ionic Liquid as Supports for Immobilization of Pancreatic Lipase.

Enzymes are difficult to recycle, which limits their large-scale industrial applications. In this work, an ionic liquid-modified magnetic metal–organic framework composite, IL-Fe3O4@UiO-66-NH2, was prepared and used as a support for enzyme immobilization. The properties of the support were characterized with X-ray powder diffraction (XRD), Fourier-transform infrared (FTIR) spectra, transmission electron microscopy (TEM), scanning electronic microscopy (SEM), and so on. The catalytic performance of the immobilized enzyme was also investigated in the hydrolysis reaction of glyceryl triacetate. Compared with soluble porcine pancreatic lipase (PPL), immobilized lipase (PPL-IL-Fe3O4@UiO-66-NH2) had greater catalytic activity under reaction conditions. It also showed better thermal stability and anti-denaturant properties. The specific activity of PPL-IL-Fe3O4@UiO-66-NH2 was 2.3 times higher than that of soluble PPL. After 10 repeated catalytic cycles, the residual activity of PPL-IL-Fe3O4@UiO-66-NH2 reached 74.4%, which was higher than that of PPL-Fe3O4@UiO-66-NH2 (62.3%). In addition, kinetic parameter tests revealed that PPL-IL-Fe3O4@UiO-66-NH2 had a stronger affinity to the substrate and, thus, exhibited higher catalytic efficiency. The results demonstrated that Fe3O4@UiO-66-NH2 modified by ionic liquids has great potential for immobilized enzymes.

Enhanced photoelectrochemical water oxidation on BiVO4 by addition of ZnCo-MOFs as effective hole transfer co-catalyst

Solar-driven water splitting is one of greenways for massive conversion of sustainable and nonpolluting energy applied to meet global energy crisis. Photocatalysts are greatly explored to improve photoelectrochemical (PEC) water oxidation efficiency. Bismuth vanadate (BiVO4) has been extensively used as photocatalyst for water oxidation, but its passive oxygen evolution kinetics and charge carrier recombination lead to inferior PEC performance under light illumination. Tuning interfacial charge separation and transfer is an eminent way to stimulate water oxidation characteristics of BiVO4. Herein, a BiVO4/zinc cobalt metal-organic framework (ZnCoMOF) composite is firstly proposed as photocatalyst for water oxidation. ZnCoMOF nanosheets are loaded on BiVO4 surface as co-catalyst via solvothermal process. Effects of solvothermal duration and mole ratio of zinc and cobalt are investigated. The optimal BiVO4/ZnCoMOF electrode shows a photocurrent density of 3.08 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE), which is 4.21 times greater than that of BiVO4 electrode. The redox properties of high valence metal ions in ZnCoMOF are used to store photoexcited holes and transfer them to the water oxidation process in the BiVO4/ZnCoMOF system. This work demonstrates that PEC performance of BiVO4 can be largely improved via controlling water oxidation kinetics and refining charge recombination and transport properties.

Removal of Hg2+ in wastewater by grafting nitrogen/sulfur-containing molecule onto Uio-66-NH2: from synthesis to adsorption studies.

The remediation of heavy metal deserves to be on the agenda, with the adsorbent design bearing the brunt of it. In this study, the molecule (4, 6-diamino-2-mercaptopyrimidine, DMP)containing thiol (-SH) and amino (-NH2) functional groups was grafted onto Uio-66-NH2, and a composite metal-organic framework nanomaterial (Zr(NH2)-DMP) was synthesized via a facile post-modification scheme. The morphological characteristics and structural features of the modified adsorbent were characterized by XRD, FT-IR, FE-SEM, EDS, BET, and XPS. The characterization results verified that the post-modification scheme was successfully achieved. The adsorption experiments were carried out to investigate the removal performance of the Zr(NH2)-DMP towards Hg2+ under different influencing parameters. The maximum adsorption capacity of 389.4mg/g was obtained, and the adsorption equilibrium was achieved within 30min at pH 6 at room temperature. Adsorption thermodynamic study indicated that the adsorption process was exothermic and spontaneous. The Zr(NH2)-DMP exhibited excellent selectivity for Hg2+, and also has the potential to remove Cu2+, Fe2+, and Zn2+ ions. The introduction of Cl- inhibited the removal of Hg2+ due to the formation of mercuric chlorides (removal efficiency reduced from 97.8 to 95.6%). The removal efficiency of up to 86.7% was obtained after four cycles. The Langmuir isotherm and Pseudo-second kinetic were more suitable for fitting the adsorption process of Hg2+ by Zr(NH2)-DMP. The main removal mechanism could be attributed to the chelation between Hg2+ (soft acid) and nitrogen/sulfur (soft base) elements. These findings convinced that the successful synthesis of Zr(NH2)-DMP provides an option for Hg2+ removal from wastewater.

Controllable self-assembled flower-like FeS with N-doped carbon coating anchored on S-doped reduced graphene oxide as high-performance lithium-ion battery anode

Iron sulfide (FeS) was supposed to be a suitable substitute for the commonly used graphite anode in lithium-ion batteries due to its higher specific capacity. However, its electrochemical property was severely limited due to its weak conductivity and evident volume change. To address these issues, we successfully construct controllable self-assembled flower-like with N-doped carbon coating FeS anchored on S-doped reduced graphene oxide (FeS/C@rGO) nanocomposites, used the synthesized octahedron iron-based metal-organic framework and graphene oxide composite (Fe-MOF@GO) as the precursor and thioacetamide as the sulfur via high-temperature calcination. The flower-like structure was generated by the controllable self-assembly of FeS nanosheets following an octahedral collapse, which enhanced the contact area between the active material and the electrolyte and improved Li+ transmission efficiency. Furthermore, the N-doped carbon and rGO efficiently inhibits the volume growth and aggregation of FeS nanosheets, resulting in the fabrication of controllable self-assembled flower-like FeS/C@rGO with a stable structure and outstanding rate performance. The discharge capacities of the FeS/C@rGO electrode were 1446.3, 1379.4, 1266.7, 1179.2, 1097.5 and 980.7 mAh g−1 at different current densities of 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 A g−1, respectively. When the current density returns to 0.1 A g−1, the reversible capacity is restored to 1629.7 mAh g−1. Moreover, the reversible specific capacity of FeS/C@rGO anode was 1428.2 mAh g−1 (130 cycles) at 0.1 A g−1 current density, showing excellent cycling performance.

PH/redox/α-amylase triple responsive metal-organic framework composites for pest management and plant growth promotion

The development of stimuli-responsive controlled release formulations is a promising strategy to enhance the utilization efficiency and reduce the environmental pollution of pesticides. In this work, a smart pH/redox/α-amylase triple stimuli-responsive pesticide delivery system was constructed by bonding carboxymethyl starch (CMS) with metal-organic frameworks (MIL-101(Fe)–NH2 nanoparticles) which loaded with CAR (CAR@MIL-101(Fe)-CMS nanoparticles). The results indicated that the loading capacity of CAR@MIL-101(Fe)-CMS nanoparticles for CAR was approximately 18.3% and the CMS attached on the surface of CAR@MIL-101(Fe)–NH2 nanoparticles could protect CAR from photolysis effectively. Meanwhile, the coated CMS and metal-organic framework structure of the nanoparticles could be decomposed and consequently release pesticide active ingredients on demand when CAR@MIL-101(Fe)-CMS nanoparticles were metabolized by glutathione and α-amylase in the insect alkaline midgut. The bioactivity survey confirmed that CAR@MIL-101(Fe)-CMS nanoparticles had a longer duration in controlling Spodoptera frugiperda larvae compared to CAR suspension concentrate. In addition, the MIL-101(Fe)-CMS nanocarriers were safe for the growth of maize and could be used as fertilizer to promote the growth and development of crops. Thus, this smart stimuli-responsive pesticide-fertilizer all-in-one combination strategy has great potential in pest management.

Techniques for remediation of pharmaceutical pollutants using metal organic framework - Review on toxicology, applications, and mechanism

Treatment of recalcitrant and xenobiotic pharmaceutical compounds in polluted waters have gained significant attention of the environmental scientists. Antibiotics are diffused into the environment widely owing to their high usages, very particularly in the last two years due to over consumption during covid 19 pandemic worldwide. Quinolones are very effective antibiotics, but do not get completely metabolized due to which they pose severe health hazards if discharged without proper treatment. The commonly reported treatment methods for quinolones are adsorption and advanced oxidation methods. In both the treatment methods, metal organic frameworks (MOF) have been proved to be promising materials used as stand-alone or combined technique. Many composite MOF materials synthesized from renewable, natural, and harmless materials by eco-friendly techniques have been reported to be effective in the treatment of quinolones. In the present article, special focus is given on the abatement of norfloxacin and ofloxacin contaminated wastewater using MOFs by adsorption, oxidation/ozonation, photocatalytic degradation, electro-fenton methods, etc. However, integration of adsorption with any advanced oxidation methods was found to be best remediation technique. Of various MOFs reported by several researchers, the MIL-101(Cr)–SO3H composite was able to give 99% removal of norfloxacin by adsorption. The MIL – 88A(Fe) composite and Fe LDH carbon felt cathode were reported to yield 100% degradation of ofloxacin by photo-Fenton and electro-fenton methods respectively. The synthesis methods and mechanism of action of MOFs towards the treatment of norfloxacin and ofloxacin as reported by several investigation reports are also presented.