Construction of flexible metal-organic framework (MOF) papers through MOF growth on filter paper and their selective dye capture

pH-triggered polydopamine-decorated nanocellulose membranes for continuously selective separation of organic dyes

Membrane separation technology has emerged as a powerful tool to separate organic dyes from industrial wastewater. However, continuously selective separation of organic dyes with similar molecular weight remains challenging. Herein, we presented a pH-triggered membrane composed of polydopamine-decorated tunicate-derived cellulose nanofibers (PDA@TCNFs) for selective separation of organic dyes. Such self-supporting membranes with nanoporous structure were fabricated by facile vacuum-assisted filtration of PDA@TCNF suspension. The incorporation of polydopamine not only enhanced the stability of the membranes, but also endowed membranes with excellent pH sensitivity, facilitating the continuously selective separation of organic dyes. These pH-triggered PDA@TCNF membranes could selectively separate Methyl Orange (MO) and Rhodamine B (RB) from the MO/RB mixed solution by switching the pH values. The continuously selective separation of the MO/RB mixed solution was demonstrated, where both MO and RB recovery ratios maintained at ∼99 % during 50 repeated cycles. This work provides a new strategy to develop a pH-triggered sustainable nanocellulose-based membrane for continuously selective separation of mixed dyes.

Hydrazone-linked covalent organic framework functionalized with cysteine as a fluorescence sensor and Exploration of paper chip for p-nitrophenol detection

The large use and emission of p-nitrophenol (p-NP) seriously pollute the environment and endanger human health. In this work, a hydrazone-linked fluorescent covalent organic framework (BATHz-COF) was simply synthesized at room temperature and covalently linked N-acetyl-L-cysteine (NALC) via the "thiol-ene" click reaction, where carboxyl groups were introduced to improve dispersion and fluorescence intensity. As a rapid, good selectivity and reusability fluorescence sensor, the obtained COF-NALC has been used for quantitative analysis of p-NP predicated on the internal filtering effect (IFE). Under optimal conditions, COF-NALC enabled quantitative detection of p-NP with a linear range of 5-50 μM and the detection limit was 1.46 μM. The application of COF-NALC to the detection of p-NP in river water samples was successful, and the satisfactory recoveries were 98.0%-109.3%. Furthermore, the fluorescent COF paper chips constructed by in situ growth were combined with a smartphone to build a visual platform for the quick and real-time detection of p-NP, providing an excellent illustration for the development of intelligent fluorescence sensing in environmental analysis.

A Drop-and-Drain Method for Convenient and Efficient Fabrication of MOF/Fiber Composites

The fabrication of flexible composites by integrating metal-organic frameworks (MOFs) with flexible substrates is a critical strategy for developing advanced materials with excellent feasibility and processability. These flexible MOF-based composites play a particularly important role in the separation and purification processes. However, several drawbacks remain challenge to overcome such as long processing time, high-cost, complicated processes, or harsh reaction conditions. In this paper, a convenient and efficient method is reported for fabricating MOF/fiber composites using a simple drop-and-drain (D&D) process. By exploiting the electrostatic interactions between the positively charged MOF particles and negatively charged fiber-based flexible substrates, a uniform coating of MOF on flexible fibers are achieved. This is accomplished by allowing the MOF ink to drop and drain through a substrate using a custom-made Teflon cell. Additionally, the D&D method enables the production of multiple layers of composites in a single-step process. UiO-66 and ZIF-8 submicroparticles and various substrates such as cotton-pad, cotton-fabric, nylon-fabric, PET-fabric, and filter-paper are employed to create flexible MOF/fiber composites. These composites demonstrate outstanding capacities for capturing negatively charged organic dyes, including methyl orange and indigo carmine. Furthermore, the MOF/fiber composites can be reused for dye capture after a simple washing process.

Recent trends in wastewater treatment by using metal-organic frameworks (MOFs) and their composites: A critical view-point

Respecting the basic need of clean and safe water on earth for every individual, it is necessary to take auspicious steps for waste-water treatment. Recently, metal-organic frameworks (MOFs) are considered as promising material because of their intrinsic features including the porosity and high surface area. Further, structural tunability of MOFs by following the principles of reticular chemistry, the MOFs can be functionalized for the high adsorption performance as well as adsorptive removal of target materials. However, there are still some major concerns associated with MOFs limiting their commercialization as promising adsorbents for waste-water treatment. The cost, toxicity and regenerability are the major issues to be addressed for MOFs to get insightful results. In this article, we have concise the current strategies to enhance the adsorption capacity of MOFs during the water-treatment for the removal of toxic dyes, pharmaceuticals, and heavy metals. Further, we have also discussed the role of metallic nodes, linkers and associated functional groups for effective removal of toxic water pollutants. In addition to conformist overview, we have critically analyzed the MOFs as adsorbents in terms of toxicity, cost and regenerability. These factors are utmost important to address before commercialization of MOFs as adsorbents for water-treatment. Finally, some future perspectives are discussed to give directions for potential research.

In situ facile synthesis and antibacterial activity of Ag-MOFs/cellulose filter paper composites for fruit fresh-keeping

A large number of fresh fruits are wasted in the supply chain due to spoilage, so it is crucial to develop fruit preservation materials. Herein, two novel Ag-MOFs/carboxymethyl filter paper (Ag-MOFs/CMFP) composites were successfully synthesized by in situ facile synthesis, which can be used as packaging materials to delay fruit spoilage. The synthesis process is simple and environmentally friendly, and the reaction conditions are mild. The mechanical property, water stability, and antibacterial activity of the as-synthesized Ag-MOFs/CMFP composites were investigated. Specifically, the composites exhibited high mechanical performance and the tensile strength was >10.00 MPa. Moreover, the composites displayed good water stability and can remain stable in water environment for >7 days, which can be attributed to the strong interaction between Ag-MOFs and CMFP. Significantly, Ag-MOF particles endow the composite papers with excellent antibacterial activity, which can inactivate 99.9 % of the bacteria. Attributed to these characteristics, these composite papers were used as fruit fresh-keeping materials and can prolong the shelf-life of cherry tomatoes and peaches for >10 days. This research not only provides a facile synthesis strategy for the flexible MOFs paper, but also provides instructive guidance for related research on fruit preservation materials.

Nanoarchitectonics of Bimetallic MOF@Lab-Grade Flexible Filter Papers: An Approach Towards Real-Time Water Decontamination and Circular Economy

This study presents a novel approach to decontaminate ferrocyanide-contaminated wastewater. The work effectively demonstrates the use of bimetallic Mo/Zr-UiO-66 as a super-adsorbent for rapid sequestration of Prussian blue, a frequently found iron complex in cyanide-contaminated soils/groundwater. The exceptional performance of Mo/Zr-UiO-66 is attributed to the insertion of secondary metallic sites, which deliver synergistic effects, benefiting the inherent qualities of the framework. Moreover, to extend the industrial applications of metal-organic frameworks (MOFs) in real-world scenarios, an approach is delivered to structure the nanocrystalline powders into MOF-based macrostructures. The work demonstrates an interfacial process to develop continuous MOF nanostructures on ordinary laboratory-grade filter papers. The novelty of the work lies in the development of robust free-standing filtration materials to purify PB dye-contaminated water. Additionally, the work embraces a circular economy concept to address problems related to resource scarcity, excessive waste production, and maintenance of economic benefits. Consequently, the PB dye-loaded adsorbent waste is re-employed for the adsorption of heavy metals (Pb2+ and Cd2+ ). Simultaneously, the study aims to address the problems related to the real-time handling of powdered adsorbents, and the generation of ecologically harmful secondary waste, thereby, progressing toward a more sustainable system.

Design of amphoteric MOFs-cellulose based composite for wastewater remediation: Adsorption and catalysis

Water pollution remains a serious problem for aquatic organism and human beings. Developing an efficient material which can simultaneously remove and convert pollutants into low or no harmful compounds is an essential issue. Targeting at this goal, a multifunctional and amphoteric wastewater treatment material of Co-MOF and functionalized cellulose-based composite (CMC/SA/PEI/ZIF-67) was designed and prepared. Carboxymethyl cellulose (CMC) and sodium alginate (SA) were selected as support to construct an interpenetrating network structure and made it crosslinked with polyethyleneimine (PEI) for further in situ growth of ZIF-67 with good dispersion. The material was characterized using an appropriate set of spectroscopic and analytical techniques. When applied in the adsorption of heavy metal oxyanions with no adjustment of pH, the adsorbent could completely decontaminate Cr(VI) at both low and high initial concentrations with good reduction rates. The adsorbent maintained good reusability after five cycles. Meanwhile, the cobalt species of CMC/SA/PEI/ZIF-67 can activate peroxymonosulfate to generate high oxidizing substances (such as SO4-· and ·OH- radicals) to degrade cationic rhodamine B dye within 120 min, thus indicating the amphoteric and catalytic nature of our CMC/SA/PEI/ZIF-67 adsorbent. The mechanism of the adsorption and catalytic process was also discussed based with the assistance of different characterization analysis.

Fabrication of Cellulose Filters Incorporating Metal-Organic Frameworks for Efficient Nicotine Adsorption from Cigarette Smoke

To prevent negative effects of smoking, there is constant research on the development of various types of sustainable filter materials, capable of removing toxic compounds present in cigarette smoke. Because of the extraordinary porosity and adsorption properties, metal-organic frameworks (MOFs) represent promising adsorbents for volatile toxic molecules such as nicotine. This study reports new hybrid materials wherein six types of common MOFs of different porosity and particle size are incorporated into sustainable cellulose fiber from bamboo pulp, resulting in a series of cellulose filter samples abbreviated as MOF@CF. The obtained hybrid cellulose filters were fully characterized and investigated in nicotine adsorption from cigarette smoke, using a specially designed experimental setup. The results revealed that the UiO-66@CF material features the best mechanical performance, facile recyclability, and excellent nicotine adsorption efficiency that attains 90% with relative standard deviations lower than 8.80%. This phenomenon may be caused by the large pore size, open metal sites, and high loading of UiO-66 in cellulose filters. Additionally, the high adsorption capacity showed almost 85% removal of nicotine after the third adsorption cycle. The DFT calculation methods allowed further investigation of the nicotine adsorption mechanism, showing that the energy difference between HOMO and LUMO for UiO-66 was the closest to that of nicotine, which further proves the adsorption ability of nicotine by this material. Owing to the flexibility, recyclability, and excellent adsorption performance, the prepared hybrid MOF@CF materials may find prospective applications in nicotine adsorption from cigarette smoke.

Ring-Oven-Assisted In Situ Synthesis of Metal-Organic Frameworks on the Lab-On-Paper Device for Chemiluminescence Detection of Nitrite in Whole Blood

In situ synthesis of metal-organic frameworks (MOFs) on flexible materials for the fabrication of functional platforms and micro-devices is challenging. The time-/precursor-consuming procedure and uncontrollable assembly are stumbling blocks for constructing this platform. Herein, a novel in situ MOF synthesis method on paper substrates by use of the ring-oven-assisted technique was reported. Utilizing the ring-oven's heating and washing function, MOFs can be synthesized in 30 min on the designated position of paper chips with extremely low-volume precursors. The principle of this method was explained by steam condensation deposition. The MOFs' growth procedure was theoretically calculated by crystal sizes and the results conformed to the Christian equation. As different MOFs (Cu-MOF-74, Cu-BTB, Cu-BTC) can be synthesized successfully on paper-based chips, the ring-oven-assisted in situ synthesis method has great generality. Then, the prepared Cu-MOF-74 loading paper-based chip was applied to the chemiluminescence (CL) detection of nitrite (NO₂^-), based on the catalysis effect of Cu-MOF-74 on the NO₂^--H₂O₂ CL system. Also, by the delicate design of the paper-based chip, NO₂^- can be detected with the detection limit (DL) of 0.5 nM in whole blood samples without sample pretreatment. This work establishes a distinctive method for the in situ synthesis of MOFs and the application of MOFs on paper-based CL chips.

Enhanced removal of oxytetracycline from wastewater using bimetallic Fe/Ni nanoparticles combined with ZIF-8 nanocomposites

The integration of metal-organic frameworks with other functional materials has recently emerged as a promising approach for creating innovative materials for environmental remediation. Here, a nano-sized iron/nickel (Fe/Ni) functionalized zeolitic imidazolate framework-8 (ZIF-8-Fe/Ni) was fabricated for oxytetracycline (OTC) removal from wastewater. Cyclic voltammetry and amperometric I-t measurements indicated that OTC was degraded by ZIF-8-Fe/Ni. X-ray diffraction spectroscopy (XRD), transmission electron microscopy mapping (TEM-mapping) and X-ray photoelectron spectroscopy (XPS) indicated that Fe/Ni was evenly dispersed throughout ZIF-8 and partially oxidized after reaction with OTC. OTC adsorption isotherms and kinetics best fitted the Langmuir isotherm (R² > 0.982) and pseudo-second-order model (R² > 0.997), respectively. Reduction kinetics data followed the pseudo-first-order model (R² > 0.905), where the apparent activation energy (Ea) was 22.9 kJ mol^-1, demonstrating that OTC degradation was mainly via a chemical process. The practical removal efficiency of OTC from real wastewater by ZIF-8-Fe/Ni was 92.6%, where even after application of ZIF-8-Fe/Ni for 5 consecutive removal cycles, a high OTC removal of 74.9% was maintained. Thus ZIF-8-Fe/Ni exhibited both high removal efficiency and good recyclability.

Diatomite Composited with a Zeolitic Imidazolate Framework for Removing Phosphate from Water

Adsorption technology based on various adsorbents has been widely applied in wastewater treatment containing phosphate. A novel diatomite adsorbent composited with ZIF-8 (CZD) was developed for removing phosphate from water in this work. The chitosan was used to pre-modify the diatomite so that ZIF-8 could be anchored on the surface of the diatomite solidly and uniformly. The diatomite composited with ZIF-8 was then used to remove phosphate in water by an adsorption process, the process variables such as adsorption time, temperature, pH, and competitive ions were investigated. The electrostatic attraction was the primary mechanism of phosphate removal. The adsorption reached equilibrium within 90 min, and its sorption capacity increased when adsorption time and temperature increased. Especially, CZD had a rapid adsorption rate and 85% of the phosphate in the solution can be adsorbed within the first 10 min. The maximum phosphate adsorption capacities of the modified diatomite reached 13.46, 13.55, and 13.95 mg/g at 25, 35, and 45 °C, respectively. The removal efficiencies of CZD for phosphate were more than 98% and even came up to 100% at 45 °C. The adsorption isotherms fit well with the Langmuir isotherm model. The Freundlich isotherm and Temkin isotherm showed that the adsorption process is physical in nature. The kinetic data of the adsorption process were fitted by the pseudo-second-order kinetics. Thermodynamic parameters indicated that the adsorption process was endothermic. This adsorbent provided an alternative for phosphate removal on account of the high adsorption efficiency in a short time. Therefore, CZD could be a promising and eco-friendly phosphate adsorbent for wastewater treatment.

ZIF-8-derived photocatalyst membrane for water decontamination: From static adsorption-degradation to dynamic flow removal

Photocatalysis has been considered a promising method for environmental purification. However, powder nanomaterials are not suitable for large-scale application due to the limit of low recyclability and energy-intensive operation. Integrating and depositing powder photocatalysts on monolithic substrates may solve these issues. In this study, a ZIF-8 photocatalyst membrane and its derived product (ZnS photocatalyst membrane) was constructed by a facile in-situ treatment of cellulose-based substrate (take filter paper as an example). Both the two nanomaterials were confirmed to be tightly anchored to filter paper with the aid of chemical interaction. Under visible light irradiation, excellent dynamic-flow photocatalytic removal efficiencies of methylene blue (MB) degradation (97% within 80 min, k = 0.042 ± 0.002 min^-1) and Cr(VI) reduction (100% within 60 min, k = 0.116 ± 0.007 min^-1) were achieved by the prepared ZIF-8 photocatalyst membrane and its derived ZnS photocatalyst, respectively. Considering the high MB adsorption capacity and facile regeneration process of ZIF-8 photocatalyst membrane, the adsorption-degradation strategy was promising for its universal applications. The MB degradation pathway and photocatalytic mechanisms were also explored. Ultimately, a comprehensive discussion on the advantages and implications of prepared photocatalyst membranes for photocatalytic water treatment was rationally proposed. This study provided a promising method for water decontamination and demonstrated the significant superiority of monolithic membrane for photocatalytic water treatment.

Cellulose filter paper immobilized α-glucosidase and its application to screening inhibitors from traditional Chinese medicine

In this study, α-glucosidase was successfully immobilized on cellulose filter paper and further applied to screening inhibitors from traditional Chinese medicines combined with CE analysis. For α-glucosidase immobilization, cellulose filter paper was used as the carrier and grafted with amino groups by coating chitosan, then α-glucosidase was covalently bonded on the amino-modified carrier via epoxy ring-opening reaction using polyethylene glycol diglycidyl ether as the crosslinker. Several parameters influencing the enzyme immobilization were optimized and the optimal values were enzyme concentration of 4 U mL^-1 , polyethylene glycol diglycidyl ether concentration of 1.25%, chitosan concentration of 7.5 mg mL^-1 , immobilization pH 7.0, crosslinking time of 4 h and immobilization time of 2 h. The immobilized α-glucosidase exhibited good batch-to-batch reproducibility (RSD = 2.1%, n = 5), excellent storage stability (73.5% of its initial activity after being stored at 4°C for 15 days) and reusability (75% of its initial activity after 10 repeated cycles). The Michaelis constant of immobilized α-glucosidase and half-maximal inhibitory concentration of acarbose were calculated to be 1.12 mM and 0.38 μM, respectively. Finally, the immobilized α-glucosidase was used for screening inhibitors from 14 kinds of Traditional Chinese Medicine extracts, and Sanguisorbae Radix showed the strongest inhibitory effect on α-glucosidase. This article is protected by copyright. All rights reserved.

Recent advances in metal-organic framework membranes for water treatment: A review

Among many separation membranes reported to date, the favorable polymer affinity and unique physio-chemical performances of metal-organic frameworks (MOFs) including ultra-high surface area, regular and highly controlled porosity have drawn widespread attention in industrial and academic communities. In this comprehensive review, the developmental timeline of MOF containing membranes for water treatment were clarified. The removal efficiencies, elimination mechanisms, as well as possible influencing factors of various MOF containing membranes that applied to water treatment were systematically summarized. The excellent removal performances of MOF containing membranes for various pollutants were determined by the size-exclusion, π-π stacking interaction, electrostatic interaction, hydrogen bonding and so on. Since the progress of engineered MOF containing membranes for practical wastewater treatment applications lags, we further analyzed the potential environmental application of MOF containing membranes from four aspects (stability of MOFs, antifouling performance of membranes, compatibility between MOF fillers and polymer matrix, dispersity of MOF nanoparticles in matrix), hoping to provide some meaningful insights.

Hybrid Metal-Organic Framework-Cellulose Materials Retaining High Porosity: ZIF-8@Cellulose Nanofibrils

Metal-organic frameworks have attracted a great deal of attention for future applications in numerous areas, including gas adsorption. However, in order for them to reach their full potential a substrate to provide an anchor may be needed. Ideally, this substrate should be environmentally friendly and renewable. Cellulose nanofibrils show potential in this area. Here we present a hybrid material created from the self-assembly of zeolitic imidazolate framework (ZIF-8) nanocrystals on cellulose nanofibrils (CNF) in aqueous medium. The CNF/ZIF-8 was freeze dried and formed free standing materials suitable for gas adsorption. A BET area of 1014 m2 g−1 was achieved for the CNF/ZIF-8 hybrid materials ZIF-8@cellulose which is comparable with reported values for free standing ZIF-8 materials, 1600 m2 g−1, considering the dilution with cellulose, and a considerable enhancement compared to CNF on its own, 32 m2 g−1.

In-situ growth of zeolitic imidazolate frameworks into a cellulosic filter paper for the reduction of 4-nitrophenol

Whatman® cellulosic filter paper was used as a substrate for the synthesis of two zeolitic imidazolate frameworks (ZIFs); ZIF-8 and ZIF-67 with and without 2,2,6,6-tetramethyl-1-piperidine oxoammonium salt (TEMPO)-oxidized cellulose nanofibril (TOCNF). All synthesis procedures take place at room temperature via a one-pot procedure. The synthesis steps were followed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transforms infrared (FT-IR). Data indicated the formation of metal oxide that converted to a pure phase of ZIFs after the addition of the organic linker i.e. 2-methyl imidazole (Hmim). The materials were characterized using XRD, FT-IR, SEM, energy dispersive X-ray (EDX), nitrogen adsorption-desorption isotherms, and X-ray photoelectron microscope (XPS). Data analysis confirms the synthesis of ZIFs into Whatman® filter paper. The materials were used for the reduction of pollutants such as 4-nitrophenol (4-NP) compound to 4-aminophenol (4-AP). The materials exhibit high potential for water treatment and may open new exploration for hybrid materials consisting of cellulose and ZIFs.

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.

Rational Design and Growth of MOF-on-MOF Heterostructures

Multiporous metal-organic frameworks (MOFs) have emerged as a subclass of highly crystalline inorganic-organic materials, which are endowed with high surface areas, tunable pores, and fascinating nanostructures. Heterostructured MOF-on-MOF composites are recently becoming a research hotspot in the field of chemistry and materials science, which focus on the assembly of two or more different homogeneous or heterogeneous MOFs with various structures and morphologies. Compared with one single MOF, the dual MOF-on-MOF composites exhibit unprecedented tunability, hierarchical nanostructure, synergistic effect, and enhanced performance. Due to the difference of inorganic metals and organic ligands, the lattice parameters in a, b, and c directions in the single crystal cells could bring about subtle or large structural difference. It will result in the composite material with distinct growth methods to obtain secondary MOF grown from the initial MOF. In this review, the authors wish to mainly outline the latest synthetic strategies of heterostructured MOF-on-MOFs and their derivatives, including ordered epitaxial growth, random epitaxial growth, etc., which show the tutorial guidelines for the further development of various MOF-on-MOFs.

Zinc Metal-Organic Framework Growing on the Surface of Fruit Peels and Its Photocatalytic Activity

The development of water treatment materials using environmentally friendly natural biomasses as substitutes plays an increasingly important role in environmental protection. Zeolitic imidazolate framework-8 (ZIF-8) is often used for the catalytic degradation of dye wastewater, but due to its small particle size, its disadvantage of easy agglomeration prevents it from being fully functional. Herein, we report an efficient method for synthesizing biomasses/ZIF-8 using four different fruit peels as carriers. ZIF-8 nanoparticles are in-situ grown uniformly on their surface. The Brunauer-Emmett-Teller surface area of shaddock peel/ZIF-8 was found to be 752.15 m²g^-1. After catalytic activity comparison, the loose shaddock peel/ZIF-8 showed the fastest and most significant degradation efficiency of 94% in methylene blue aqueous solution and could be used multiple times through a simple washing process.

UiO-66 metal-organic frameworks/gold nanoparticles based substrates for SERS analysis of food samples

Recently, metal-organic frameworks (MOFs) based substrates have shown great potential for the quantitative analysis of food samples by surface-enhanced Raman scattering (SERS) due to their unique properties. Herein, we developed two UiO-66 MOFs/gold nanoparticles (AuNPs) based substrates by self-assembly, including UiO-66/AuNPs suspension substrate and UiO-66(NH₂)/AuNPs/Nylon-66 flexible membrane substrate, for quantitative analysis of complex food samples by SERS. UiO-66/AuNPs suspension substrate was prepared for SERS-based determination of a carcinogenic heterocyclic amine in barbecue meat. UiO-66(NH₂)/AuNPs/Nylon-66 membrane substrate was fabricated for the simultaneous separation, enrichment, and in situ analysis of Sudan Red 7B in chilli products. The heterocyclic amine and Sudan dye in real samples could be detected and quantified with the recoveries of 82.3-110% and 84.5-114% and relative standard deviations (RSDs) of 3.1-11.0% and 1.9-5.6% (n = 3) by use of these two substrates, respectively. These two UiO-66/AuNPs based substrates combined molecular enrichment and SERS activity, achieving excellent analytical accuracy and widening SERS application in practical food safety analysis.

Performance Fabrics Obtained by In Situ Growth of Metal-Organic Frameworks in Electrospun Fibers

Metal-organic frameworks (MOFs) exhibit an exceptional surface area-to-volume ratio, variable pore sizes, and selective binding, and hence, there is an ongoing effort to advance their processability for broadening their utilization in different applications. In this work, we demonstrate a general scheme for fabricating freestanding MOF-embedded polymeric fibers, in which the fibers themselves act as microreactors for the in situ growth of the MOF crystals. The MOF-embedded fibers are obtained via a two-step process, in which, initially, polymer solutions containing the MOF precursors are electrospun to obtain microfibers, and then, the growth of MOF crystals is initiated and performed via antisolvent-induced crystallization. Using this approach, we demonstrate the fabrication of composite microfibers containing two types of MOFs: copper (II) benzene-1,3,5-tricarboxylic acid (HKUST-1) and zinc (II) 2-methylimidazole (ZIF-8). The MOF crystals grow from the fiber's core toward its outer rims, leading to exposed MOF crystals that are well rooted within the polymer matrix. The MOF fibers obtained using this method can reach lengths of hundreds of meters and exhibit mechanical strength that allows arranging them into dense, flexible, and highly durable nonwoven meshes. We also examined the use of the MOF fiber meshes for the immobilization of the enzymes catalase and horse radish peroxidase (HRP), and the enzyme-MOF fabrics exhibit improved performance. The MOF-embedded fibers, demonstrated in this work, hold promise for different applications including separation of specific chemical species, selective catalysis, and sensing and pave the way to new MOF-containing performance fabrics and active membranes.

A self-made portable separation device based on 2-D MOF nanosheets for the efficient separation of dyes in solutions

Herein we reported a simple and economical method for fabricating a portable separation device based on 2D-MOF nanosheets, which can be used disposably for a special purpose due to the low cost, simple manufacturing process in an emergency.

Practical MOF Nanoarchitectonics: New Strategies for Enhancing the Processability of MOFs for Practical Applications

Over the past decades, the development of porous materials has directly or indirectly affected industrial production methods. Metal-organic frameworks (MOFs) as an emerging class of porous materials exhibit some unique advantages, including controllable composition, a large surface area, high porosity, and so on. These attractive characteristics of MOFs have led to their potential applications in energy storage and conversion devices, drug delivery, adsorption and storage, sensors, and other areas. However, powdered MOFs have limited practical applications owing to poor processability, safety hazards from dust formation, and poor recyclability. In addition, the inherent micro/mesoporosities of MOFs also reduce the accessibility and diffusion kinetics for large molecules. To improve their processability for practical applications, MOFs are often deposited as MOF layers or films (i.e., MOF-coated composites) on supporting materials or are formed into 3D structured composites, such as aerogels and hydrogels. In this article, we review recent researches on these MOF composites, including their synthetic methods and potential applications in energy storage devices, heavy metal ion adsorption, and water purification. Finally, the future outlook and challenges associated with the large-scale fabrication of MOF-based composites for practical applications are discussed.

Zeolitic Imidazolate Framework-Based Composite Incorporated with Well-Dispersed CoNi Nanoparticles for Efficient Catalytic Reduction Reaction

Incorporation of metal nanocatalysts within a well-defined porous support is of great importance for stabilizing unstable metal nanocatalysts, so that they display an effective and long-lasting catalytic activity. In particular, metal-organic frameworks (MOFs) with a wide range of structures serve as excellent porous supports for stabilizing unstable nanocatalysts. In addition, the development of inexpensive metal nanocatalysts is necessary to replace expensive noble metal nanocatalysts. Herein, we report on a simple method for the preparation of porous MOF-based or carbon-based composites incorporated with catalytically active CoNi alloy nanoparticles. CoNi alloy nanoparticles were produced from the concurrent reduction of Co and Ni ions existing within a zeolitic imidazolate framework (ZIF)-based precursor material during the thermal treatment. In particular, a part of the highly porous ZIF was preserved during the thermal treatment at 400 °C, which eventually resulted in a composite of ZIF and CoNi (CoNi@ZIF). The resulting CoNi@ZIF showed excellent catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol. The synergy between the highly porous ZIF support and the well-dispersed CoNi nanoparticles within CoNi@ZIF provided an outstanding catalytic performance, even with inexpensive transition-metal nanocatalysts. Moreover, the catalytic activity of CoNi@ZIF was well conserved even after five consecutive reactions.

Shapeable Aerogels of Metal-Organic-Frameworks Supported by Aramid Nanofibrils for Efficient Adsorption and Interception

The immobilization of the metal-organic frameworks (MOFs) on aerogels has risen to be a promising approach for the combination of advantages on both sides. Shapeable MOF hybrid aerogels were obtained by the growth of MOF crystals on aramid nanofibril (ANF) aerogels to retain high porosities, crystal structures, and original stabilities of individual MOFs and the mechanical robustness, flexibility, and low density of ANFs. The MOF hybrid aerogels exhibited superior adsorption performance for organic dyes (e.g., 113.8 mg/g for methyl violet and 107 mg/g of rhodamine B), offered a simple, efficient, and extensible platform for removing organic dyes from aqueous solution continuously, with high flux (620 L/(h·m²·bar) at a thickness of ∼0.87 mm) and excellent rejection (>98%). This work provided a practicable pathway to manage MOF crystals into a shapeable and recyclable form for extended applications in wide fields.

Multifunctional polymers with interpenetrating structures: luminescence sensing, ECL behaviors, selective detection of Fe3+ ion and rapid removal of anionic dyes

Three unprecedented metal–organic frameworks with interspersed structures have been synthesized and structurally characterized.