3D, eco-friendly metal-organic frameworks@carbon nanotube aerogels composite materials for removal of pesticides in water

Metal-Organic Frameworks in Agriculture

Agrochemicals, which are crucial to meet the world food qualitative and quantitative demand, are compounds used to kill pests (insects, fungi, rodents, or unwanted plants). Regrettably, there are some important issues associated with their widespread and extensive use (e.g., contamination, bioaccumulation, and development of pest resistance); thus, a reduced and more controlled use of agrochemicals and thorough detection in food, water, soil, and fields are necessary. In this regard, the development of new functional materials for the efficient application, detection, and removal of agrochemicals is a priority. Metal-organic frameworks (MOFs) with exceptional sorptive, recognition capabilities, and catalytical properties have very recently shown their potential in agriculture. This Review emphasizes the recent advances in the use of MOFs in agriculture through three main views: environmental remediation, controlled agrochemical release, and detection of agrochemicals.

pH-Responsive On-Demand Alkaloids Release from Core-Shell ZnO@ZIF-8 Nanosphere for Synergistic Control of Bacterial Wilt Disease

Developing an effective and safe technology to control severe bacterial diseases in agriculture has attracted significant attention. Here, ZnO nanosphere and ZIF-8 are employed as core and shell, respectively, and then a pH-responsive core-shell nanocarrier (ZnO-Z) was prepared by in situ crystal growth strategy. The bactericide berberine (Ber) was further loaded to form Ber-loaded ZnO-Z (Ber@ZnO-Z) for control of tomato bacterial wilt disease. Results demonstrated that Ber@ZnO-Z could release Ber rapidly in an acidic environment, which corresponded to the pH of the soil where the tomato bacterial wilt disease often outbreak. In vitro experiments showed that the antibacterial activity of Ber@ZnO-Z was about 4.5 times and 1.8 times higher than that of Ber and ZnO-Z, respectively. It was because Ber@ZnO-Z could induce ROS generation, resulting in DNA damage, cytoplasm leakage, and membrane permeability changes so the released Ber without penetrability more easily penetrated the bacteria to achieve an efficient synergistic bactericidal effect with ZnO-Z carriers after combining with DNA. Pot experiments also showed that Ber@ZnO-Z significantly reduced disease severity with a wilt index of 45.8% on day 14 after inoculation, compared to 94.4% for the commercial berberine aqueous solution. More importantly, ZnO-Z carriers did not accumulate in aboveground parts of plants and did not affect plant growth in a short period. This work provides guidance for the effective control of soil-borne bacterial diseases and the development of sustainable agriculture.

Acrylate and Methacrylate Polymers' Applications: Second Life with Inexpensive and Sustainable Recycling Approaches

Polymers are widely employed in several fields thanks to their wide versatility and the easy derivatization routes. However, a wide range of commercial polymers suffer from limited use on a large scale due to their inert nature. Nowadays, acrylate and methacrylate polymers, which are respectively derivatives of acrylic or methacrylic acid, are among the most proposed materials for their useful characteristics like good biocompatibility, capping ability toward metal clusters, low price, potentially recyclability and reusability. Here, we discuss the advantages and challenges of this class of smart polymers focusing our attention on their current technological applications in medical, electronic, food packaging and environmental remediation fields. Furthermore, we deal with the main issue of their recyclability, considering that the current commercial bioplastics are not yet able to meet the global needs as much as to totally replace fossil-fuel-based products. Finally, the most accredited strategies to reach recyclable composites based on acrylic polymers are described.

Persistent organic pollutants: The trade-off between potential risks and sustainable remediation methods

Persistent Organic Pollutants (POPs) have become a very serious issue for the environment because of their toxicity, resistance to conventional degradation mechanisms, and capacity to bioconcentrate, bioaccumulate and biomagnify. In this review article, the safety, regulatory, and remediation aspects of POPs including aromatic, chlorinated, pesticides, brominated, and fluorinated compounds, are discussed. Industrial and agricultural activities are identified as the main sources of these harmful chemicals, which are released to air, soil and water, impacting on social and economic development of society at a global scale. The main types of POPs are presented, illustrating their effects on wildlife and human beings, as well as the ways in which they contaminate the food chain. Some of the most promising and innovative technologies developed for the removal of POPs from water are discussed, contrasting their advantages and disadvantages with those of more conventional treatment processes. The promising methods presented in this work include bioremediation, advanced oxidation, ionizing radiation, and nanotechnology. Finally, some alternatives to define more efficient approaches to overcome the impacts that POPs cause in the hydric sources are pointed out. These alternatives include the formulation of policies, regulations and custom-made legislation for controlling the use of these pollutants.

Preparation of chitosan crosslinked with metal-organic framework (MOF-199)@aminated graphene oxide aerogel for the adsorption of formaldehyde gas and methyl orange

Chitosan crosslinked with metal-organic framework (MOF-199)@aminated graphene oxide aerogel (MOF-199@AFGO/CS) were prepared to adsorb formaldehyde and methyl orange. The prepared MOF-199@AFGO/CS aerogel was well characterized via SEM, EDX, FT-IR, XRD and XPS to reveal the microstructure and composition. Besides, the mechanical property and the stability of MOF-199@AFGO/CS aerogel were investigated. The results showed that MOF-199@AFGO/CS aerogel had good stability in water, compression resilience and thermostability. The study on the ability to adsorb formaldehyde gas and methyl orange showed that the adsorption capacity of MOF-199@AFGO/CS aerogel was related to the pore size and the surface functional groups of MOF-199@AFGO/CS aerogel. When the pore size is moderate, as the amino group and MOF-199 on the aerogel increased, the adsorption capacity of formaldehyde gas (197.89 mg/g) and methyl orange (412 mg/g) can reach the maximum. Furthermore, the adsorption process at equilibrium followed the Freundlich isotherm model. The kinetic behavior was well fitted by the pseudo-second-order model, indicating chemisorption as the rate-determining step. This work can provide a reliable basis for the adsorbent to remove pollutants in different forms at the same time, and has potential application in simultaneously adsorbing liquid pollutants and gas pollutants.

Removal of organic pollutants from aqueous solution using metal organic frameworks (MOFs)-based adsorbents: A review

The development of metal organic frameworks (MOFs) has recently drawn a lot of scientific interest in water treatment due to the unique properties such as tunable porosities, large pore volumes, hierarchical structures, excellent adsorption and regeneration performances. MOFs represent an eco-friendly alternative to conventional adsorbents especially for the adsorptive removal of noxious organic pollutants from aqueous solution. Advanced MOFs' performances are justified by the introduction of functional groups, magnetic moieties, and specific foreign materials onto MOFs. This however leads to increase in the manufacturing costs of MOFs and consequently possess a huge challenge in large-scale applications. This review hence critically discusses the recent progresses in the development of MOFs-based adsorbents for the removal of selected organic pollutants (e.g., dyes, antibiotics and pesticides) from aqueous solution. Furthermore, major interaction mechanisms between MOFs and organic pollutants in response to numerous experimental conditions, such as pH, temperature, coexisting ions are put forward. Finally, some recommendations in support for designing MOFs with improved adsorption performances are also highlighted.

In situ anchoring Zn-doped ZIF-67 on carboxymethylated bacterial cellulose for effective indigo carmine capture

Zeolitic imidazolate frameworks (ZIFs) have been considered as advanced adsorption materials to alleviate dye pollution. However, the application range is limited due to the powder characteristics of ZIFs. The conjugation of ZIFs with nanocellulose is an attractive strategy to construct profitable materials. Herein, we report an in situ anchoring method for preparing novel ZIFs@carboxymethylated bacterial cellulose (ZCMBC) composite films. The resulting ZCMBC composite films show a high ZIFs loading rate and satisfactory selective indigo carmine removal efficiency. With simple methanol washing, ZCMBC composite films retain a high removal efficiency after regeneration. In addition, ZCMBC composite films also show excellent mechanical properties. The proposed adsorption mechanism and the universality of this in situ anchoring method are also discussed, indicating their application potential in the dye-contaminated wastewater treatment field.

Iron nanoparticles decorated hierarchical carbon fiber forest for the magnetic solid-phase extraction of multi-pesticide residues from water samples

This study describes a versatile, robust and fast sample pre-concentration novel method based on chemical vapour deposition grown iron nanoparticles dispersed hierarchical carbon fiber forest (Fe-ACF/CNF) for the determination of multi-pesticide residue in water samples. This method was developed by the implementation of Fe-ACF/CNF to magnetic solid-phase extraction method (MSPE) for the adsorption of twenty-nine pesticides of various classes using gas chromatography equipped with an electron capture detector. Fe-ACF/CNF was grown via tip growth mechanism and Fe-nanoparticles are moved to the tip of CNF. The presence of Fe-nanoparticles is responsible for the magnetic property of proposed adsorbents. The Fe-ACF/CNF is competent enough to extract twenty-nine pesticides of different physico-chemical characteristics from water samples. All the predominant parameters including the amount of sorbent desorption time, temperature, sonication effect, regeneration, and reusability of Fe-ACF/CNF were thoroughly investigated. Acceptable linearity was obtained in the range of 20-500 μg/L with a correlation coefficient value ≥ 0.990 for all pesticides. The accuracy of the developed method was evaluated and the obtained recovery of the spiked samples was within 70-120% (standard deviation ≤ 15%) and reusability up to the 4th cycle. The limit of detection and quantification values was in the range of 1.44-5.15 and 4.76-17.0 μg/L, respectively. The obtained results are also cross verified with real water samples from the Gomti river (Lucknow, India) and shown the excellent extraction efficiency of Fe-ACF/CNF.

A Facile Strategy for Constructing a Carbon-Particle-Modified Metal-Organic Framework for Enhancing the Efficiency of CO2 Electroreduction into Formate

Electrocatalytic reduction of CO₂ by metal-organic frameworks (MOFs) has been widely investigated, but insufficient conductivity limits application. Herein, a porous 3D In-MOF {(Me₂ NH₂ )[In(BCP)]⋅2 DMF}_n (V11) with good stability was constructed with two types of channels (1.6 and 1.2 nm diameter). V11 exhibits moderate catalytic activity in CO₂ electroreduction with 76.0 % of Faradaic efficiency for formate (FE_HCOO- ). Methylene blue molecules of suitable size and pyrolysis temperature were introduced and transformed into carbon particles (CPs) after calcination. The performance of the obtained CPs@V11 is significantly improved both in FE_HCOO- (from 76.0 % to 90.1 %) and current density (2.2 times). Control experiments show that introduced CPs serve as accelerant to promote the charges and mass transfer in framework, and benefit to sufficiently expose active sites. This strategy can also work on other In-MOFs, demonstrating the universality of this method for electroreduction of CO₂ .

Si3N4 Nanofibrous Aerogel with In Situ Growth of SiOx Coating and Nanowires for Oil/Water Separation and Thermal Insulation

Nanofibrous aerogels constructed by ceramic fiber components (CNFAs) feature lightweight, compressibility, and high-temperature resistance, which are superior to brittle ceramic aerogels assembled from nanoparticles. Up to now, in order to obtain CNFAs with stable framework and multifunctionality such as hydrophobicity and gas absorption, it is necessary to perform binding and surface modification processes, respectively. However, the microstructure as well as properties of CNFAs are deteriorated by the direct addition of binders and modifiers. To tackle these problems, we introduced a unique low-temperature (100 °C) chemical vapor deposition method (LTCVD) to achieve the cross-linking and hydrophobization of Si₃N₄ CNFA in only one step. More importantly, during the LTCVD process, SiO_x coatings and nanowire arrays were in situ formed via vapor-solid (VS) and vapor-liquid-solid (VLS) mechanisms on the surface and intersection of Si₃N₄ nanofibers, which cemented the aerogel framework, endowed it with hydrophobicity, and improved its oxidation resistance at high temperature. Compared to most of its counterparts, the Si₃N₄/SiO_x CNFA exhibited better mechanical properties, higher capability of oil/water separation (33-76 g·g^-1), lower thermal conductivity (0.0157 W/m·K^-1), and superior structural stability in a wide temperature range of -196-1200 °C. This work not only presents an excellent Si₃N₄/SiO_x CNFA for the first time but also provides fresh insights for the exquisite preparation strategy of CNFAs.

A Light-Triggered pH-Responsive Metal-Organic Framework for Smart Delivery of Fungicide to Control Sclerotinia Diseases of Oilseed Rape

Using a simple one-pot method, we developed a prochloraz (Pro) and pH-jump reagent-loaded zeolitic imidazolate framework-8 (PD@ZIF-8) composite for the smart control of Sclerotinia disease. The pH-jump reagent can induce the acidic degradation of ZIF-8 using UV light to realize the controlled release of Pro. Thus, the physical properties of PD@ZIF-8, such as its release, formulation stability, and adhesion, were investigated in detail. The results showed that the quantity of Pro released by PD@ZIF-8 under UV light irradiation (365 nm) was 63.4 ± 3.5%, whereas under dark conditions, it was only 13.7 ± 0.8%. In vitro activity indicated that the EC₅₀ of PD@ZIF-8 under UV light irradiation was 0.122 ± 0.02 μg/mL, which was not significantly different from that of Pro (0.107 ± 0.01 μg/mL). Pot experiments showed that the efficacy of PD@ZIF-8 under light irradiation was 51.2 ± 5.7% for a fungal infection at 14 days post-spraying, whereas the effectiveness of prochloraz emulsion in water was only 9.3 ± 3.3%. Furthermore, fluorescence tracking of ZIF-8 and biosafety experiments showed that ZIF-8 could be absorbed by plant leaves and transported to various parts of oilseed rape in a short period of time and that PD@ZIF-8 was relatively safe for plants and HepG2 cells. These results highlight the potential of the composite to provide efficient and smart delivery of fungicides into plants for protection against diseases and provide an idea for developing sustainable agriculture.