Highly selective and visual detection of vanillin based on fluorescence Cd-MOF sensor in milk powders.

Vanillin is a commonly used synthetic flavoring agent in daily life. However, excessive intake of vanillin may pose risks to human health. Therefore, there is an urgent need for rapid and sensitive detection methods for vanillin. In this study, we developed a fluorescent sensor based on Cd-MOF for the sensitive and selective recognition of vanillin. The presence of vanillin leads to significant fluorescence quenching of Cd-MOF due to competitive absorption and photoinduced electron transfer (PET). The limit of detection was determined to be 39.6 nM, which is the lowest-among the reported fluorescent probes. The sensor was successfully applied for the detection of vanillin in real samples such as powdered milk and milk, with a recovery rate ranging from 96.88 % to 104.83 %. Furthermore, by immobilizing the Cd-MOF probe into a polyvinyl alcohol (PVA) film, we achieved a portable and visual detection composite materials for vanillin.

Multifunctional MOF: Cold/hot adapted sustainable oxidase-like MOF nanozyme with ratiometric and color tonality for nitrite ions detection.

Integrating multiple functionalities into a single entity is highly important, especially when a broad spectrum of application is required. In the present work, we synthesized a novel manganese-based MOF (denoted as UoZ-6) that functions as a cold/hot-adapted and recyclable oxidase nanozyme (Km 0.085 mM) further developed for ratiometric-based colorimetric and color tonality visual-mode detection of nitrite in water and food. Nitrite ions promote the diazotization process of the oxTMB product, resulting in a decay in the absorbance signal at 652 nm and the emergence of a new signal at 461 nm. The dual-absorbance ratiometric platform for nitrite ion detection functions effectively across a wide temperature range (0 °C to 100 °C), offering a linear detection range of 5-45 µM with a detection limit of 0.15 µM using visual-mode. This approach is sensitive, reliable, and selective, making it effective for detecting nitrite ions in processed meat and water.

An electrochemical sensor based on 2D Zn-MOFs and 2D C-Ti3C2Tx composite materials for rapid and direct detection of various foodborne pathogens.

Rapid screening for foodborne pathogens is crucial for food safety. A rapid and one-step electrochemical sensor has been developed for the detection of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Salmonella typhimurium (S. typhimurium). Through the construction of aptamer/two-dimensional carboxylated Ti3C2Tx (2D C-Ti3C2Tx)/two-dimensional Zn-MOF (2D Zn-MOF) composites, the recognition elements, signal tags, and signal amplifiers are integrated on the electrode surface. Pathogens are selectively captured using the aptamer, which increases the impedance of the electrode surface，leads to a decrease in the 2D Zn-MOF current. Bacteria can be rapidly quantified using a one-step detection method and the replacement of aptamers. The detection limits for E. coli, S. aureus, and S. typhimurium are 6, 5, and 5 CFU·mL-1, respectively. The sensor demonstrated reliable detection capabilities in real-sample testing. Therefore, the one-step sensor based on the 2D Zn-MOF and 2D C-Ti3C2Tx has significant application value in the detection of foodborne pathogens.

Multiplicative rGO/Cu-BDC MOF for 4-nitrophenol reduction and supercapacitor applications.

Two-dimensional nanosheets, with their distinct characteristics, are widely used in various applications such as water splitting, supercapacitors, catalysis etc. In this research, we produced Cu-BDC MOF nanosheets by using Cu2O nanotubes for metal ions and H2BDC as the organic linker. We combined these Cu-BDC MOF nanosheets with reduced graphene oxide (rGO) to form a nanocomposite. The collaboration between Cu-BDC MOF and rGO boosts both the catalytic reduction of 4-nitrophenol and the electrochemical capabilities. The conversion of 4-nitrophenol to 4-aminophenol is achieved using sodium borohydride as both a reducing agent and a catalyst. The study explores the impact of different concentrations of 4-nitrophenol and sodium borohydride on catalytic efficiency. The increase in sodium borohydride concentration enhances catalytic efficiency by providing more BH4- ions and electrons for the reduction process. The catalytic reduction process adheres to the Langmuir-Hinshelwood mechanism with apparent pseudo-first-order kinetics. Specifically, Cu-BDC MOF and rGO/Cu-BDC MOF exhibit specific capacities of 468.4 mA h/g and 656.4 mA h/g at a current density of 2 A/g, respectively, while also enhancing the operating voltage window. Therefore, electrodes based on rGO/Cu-BDC MOF nanosheets present a novel approach for environmental remediation and energy storage applications across various fields.

Carbonized wood fiber-supported S, N-codoped carbon layer-coated multinary metal sulfide nanoarchitecture for efficient oxygen evolution reaction at ampere-level current density.

Multinary metal sulfides (MMSs) are highly suitable candidates for the application of electrocatalysis as they offer numerous parameters for optimizing the electronic structure and catalytic sites. Herein, a stable nanoarchitecture consisting of MMSs ((NiCoCrMnFe)Sx) nanoparticles embedded in S, N-codoped carbon (SNC) layers derived from metal organic framework (MOF) and supported on carbonized wood fibers (CWF) was fabricated by directly carbonization. Benefiting from this carbon-coated configuration, along with the synergistic effects within multinary metal systems, (NiCoCrMnFe)Sx@SNC/CWF delivers an exceptionally low overpotential of 260 mV at a high current density of 1000 mA cm-2, a small Tafel slope of 48.5 mV dec-1, and robust electrocatalytic stability. Furthermore, the (NiCoCrMnFe)Sx@SNC/CWF used as the cathode of rechargeable Zn-air batteries demonstrates higher power density and remarkable durability, surpassing that of commercial RuO2. Thus, we showcase the feasibility and advantages of employing highly efficient and durable MMSs materials for low-cost and sustainable energy conversion.

MOF-on-MOF-derived FeCo@NC OER&ORR bifunctional electrocatalysts for zinc-air batteries.

Zinc-air batteries, as one of the emerging areas of interest in the quest for sustainable energy solutions, are hampered by the intrinsically sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), and still suffer from the issues of low energy density. Herein, we report a MOF-on-MOF-derived electrocatalyst, FeCo@NC-II, designed to efficiently catalyze both ORR (Ehalf = 0.907 V) and OER (Ej=10 = 1.551 V) within alkaline environments, surpassing esteemed noble metal benchmarks (Pt/C and RuO2). Systematically characterizations and density functional theory (DFT) calculations reveal that the synergistic effect of iron and cobalt bimetallic and the optimized distribution of nitrogen configuration improved the charge distribution of the catalysts, which in turn optimized the adsorption / desorption of oxygenated intermediates accelerating the reaction kinetics. While the unique leaf-like core-shell morphology and excellent pore structure of the FeCo@NC-II catalyst caused the improvement of mass transfer efficiency, electrical conductivity and stability. The core and shell of the precursor constructed through the MOF-on-MOF strategy achieved the effect of 1 + 1 > 2 in mutual cooperation. Further application to zinc-air batteries (ZABs) yielded remarkable power density (212.4 mW/cm2), long cycle (more than 150 h) stability and superior energy density (∼1060 Wh/kg Zn). This work provides a methodology and an idea for the design, synthesis and optimization of advanced bifunctional electrocatalysts.

Insights into Thermal Conductivity at the MOF-Polymer Interface.

Understanding the thermal conductivity in metal-organic framework (MOF)-polymer composites is crucial for optimizing their performance in applications involving heat transfer. In this work, several UiO66-polymer composites (where the polymer is either PEG, PVDF, PS, PIM-1, PP, or PMMA) are examined using molecular simulations. Our contribution highlights the interface's impact on thermal conductivity, observing an overall increasing trend attributable to the synergistic effect of MOF enhancing polymer thermal conductivity. Flexible polymers such as PEG and PVDF exhibit increased compatibility with the MOF, facilitating their integration with the MOF lattice. However, this integration leads to a moderated enhancement in thermal conductivity compared to polymers that remain separate from the MOF structure, such as PS or PP. This effect can be attributed to alterations in phonon transport pathways and shifts in interfacial interactions between the polymer and MOF. Specifically, the infiltration of the polymer like PEG and PVDF into the MOF disrupted the MOF's ordered network, introducing defects or barriers that hindered phonon propagation. In contrast, nonpolar and rigid polymers like PP, PMMA, PS, and PIM-1 exhibited greater improvements in thermal conductivity when combined with MOFs compared to the flexible polymers PVDF and PEG. Most notably, our analysis identifies a critical interface region within approximately 30-50 Å that profoundly influences thermal conductivity. The interface region, as indicated by the density profile and radius of gyration, is notably shorter but plays a pivotal role in modulating the thermal properties. The sensitivity of the system to these interface characteristics underscores the crucial role of this particular interface area in dictating the thermal conductivity. Our findings emphasize the sensitivity of thermal conductivity in polymer matrices to interface characteristics and highlight the critical role of a specific interface region in modulating thermal properties.

Zwitterionic MOF-embedded alginate beads with polydopamine surface functionalization for efficient doxycycline removal: Optimization and mechanistic study.

The adsorptive removal of amphoteric antibiotics like doxycycline (DOX) is a difficult task because of the electrostatic repulsion between these amphoteric molecules and adsorbents. For this purpose, a zwitter adsorbent was fabricated by incorporating zwitter ZIF-67/MIL-88A binary MOF into the matrix of alginate (Alg); in addition, the surface of the beads was modified by polydopamine (PDA). The batch experiments implied the super-high adsorption efficacy of ZIF-67/MIL-88A@Alg@PDA toward DOX attained 384.61 ±â€¯5.08 mg/g at a neutral pH medium, 25 °C, and using 0.02 g. The isotherm analysis implied the physisorption of DOX onto ZIF-67/MIL-88A@Alg@PDA, while the kinetic analysis denoted the chemisorption of DOX. The results of XPS, Zeta potential, and Lab experiments identified the types of physical and chemical interactions between ZIF-67/MIL-88A@Alg@PDA and DOX. The durability of the ZIF-67/MIL-88A@Alg@PDA beads was inspected by the recycling test, clarifying that the DOX adsorption aptitude declined by 12.22 mg/g. In addition, the measured leaching concentrations of cobalt and iron from leaching test were 0.008 and 0.098 mg/L. The ionic strength of ZIF-67/MIL-88A@Alg@PDA, implying an enhancement in the DOX removal (%) from 83.51 to 93.50 % by raising the NaCl concentration from 0.2 to 1.0 mol/L. Therefore, our study could provide a simple procedure to overcome the electrostatic repulsion that retard the adsorption process of the amphoteric drugs onto charged adsorbents with positive or negative charges. Additionally, this procedure could also generate an electrostatic interaction between the zwitter adsorbents and the amphoteric drugs at specific pH media when they are in a zwitterionic nature.

Recent Focuses in the Syntheses and Applications of Magnetic Metal-Organic Frameworks.

In this article, we examine the recent uses of magnetic metal-organic frameworks (MMOFs). MMOFs can be used in various fields such as water purification, laboratory, food, environment, etc. Their materials can be composed of different metals and ligands, each of which has its own properties. Also, the presence of a magnetic property in these absorbents adds good features such as easy separation, faster absorption, and better interaction with other particles, which improves their application and performance. In recent years, various types of these compounds have been made, and, in this article, while classifying them, we will discuss the structure and application of some MMOFs.

Eu-MOF-based highly sensitive and selective luminescence probe for trace, in situ and visual detection of flunitrazepam.

Flunitrazepam, as an emerging new psychoactive substance classified as a third-generation drug that is more harmful and camouflaged, is gradually proliferating globally. Maliciously used as a criminal tool in homicide and rape cases, it has already caused serious harm to public safety and social stability. Owing to its special molecular structure, low concentration level and rapid metabolic process in the human body, accurate detection of flunitrazepam remains a major challenge, especially for real sample and on-site detection. In this paper, a lanthanide MOF (Eu-MOF) based on bi-ligand was constructed as a luminescence probe and used for the first time to detect trace amounts of flunitrazepam. The 'antenna effect' promotes strong luminescence of Eu-MOF, while the lower LUMO orbital energy level of flunitrazepam allows it to accept electrons from the electron donor leading to quenching of Eu-MOF luminescence. The probe has a high sensitivity and can detect flunitrazepam in the range of 0-800 µM with a detection limit as low as 73 nM. Moreover, flunitrazepam was detected in urine from real samples as well as in a variety of beverages to further validate its accuracy and practicality. The reported Eu-MOF represents one of the pioneering luminescence probes for the detection of flunitrazepam, which offers great promise for the on-site or on-line analysis of flunitrazepam.

Construction of heterogeneous MOF-on-MOF for highly efficient gaseous iodine sequestration under static conditions.

Considering the unexpected nuclear power waste emission and potential nuclear leakage, the exploration of robust materials for the effective capture and storage of radioactive iodine is of great importance but still remains a challenge. In this work, we report the rational synthesis of functionalized NH2-UiO-66-on-ZIF-67 architecture to enhance the static adsorption and retention of volatile iodine. Such MOF-on-MOF heterostructures was fabricated through seeding ZIF-67 core on the surface of NH2-UiO-66 satellite via a facile polyvinylpyrrolidone (PVP) regulated internal extended growth strategies. NH2-UiO-66-on-ZIF-67 exhibited unique core-satellite structure, which significantly promotes the binding interactions with iodine through synergizing of the N-rich imidazole moieties and surface functionalized amino groups within the porosity channels. As a result, the as fabricated NH2-UiO-66-on-ZIF-67 achieves enhanced mass diffusion and high capture capacity of 3600 mg/g for iodine vapor under static sorption conditions. Moreover, water vapor in humid conditions (relative humidity of 18 %) has almost no effect on the static iodine adsorption performance of the material. This study sheds light on a reliable MOF-on-MOF hybrid strategy for effective radioiodine treatment to ensure the safety nuclear waste management.

A glutathione-activated bismuth-gallic acid metal-organic framework nano-prodrug for enhanced sonodynamic therapy of breast tumor.

Sonodynamic therapy is a promising, noninvasive, and precise tumor treatment that leverages sonosensitizers to generate cytotoxic reactive oxygen species during ultrasound stimulation. Gallic acid (GA), a natural polyphenol, possesses certain anti-tumor properties, but exhibits significant toxicity toward normal cells, limiting its application in cancer treatment. To overcome this issue, we synthesized a bismuth-gallic acid (BGA), coordinated metal-organic framework (MOF) nano-prodrug. Upon encountering glutathione (GSH), BGA gradually dissociated and depleted GSH, releasing GA, which had anti-tumor effects. As an MOF with semiconductor properties, BGA primarily produced superoxide anion radical upon ultrasound excitation. After the release of GA, GA generated superoxide anion radical and further produced high toxic singlet oxygen under ultrasound stimulation, while further oxidizing and consuming GSH, enhancing sonocatalytic performance. Additionally, the released GA induced cell cycle arrest, ultimately leading to apoptosis. Our results revealed that BGA, as a GSH-activated, metal-polyphenol MOF nano-prodrug, showed potential for use in breast tumor sonodynamic therapy, providing a novel strategy for precise tumor treatment.

Surface-modified composites of metal-organic framework and wood-derived carbon for high-performance supercapacitors.

The renewable nature, high carbon content, and unique hierarchical structure of wood-derived carbon make it an optimal self-supporting electrode for energy storage. However, the limitations in specific surface area and electrical conductivity defects pose challenges to achieving satisfactory charge storage in wood-derived carbon electrodes. Therefore, exploring diverse and effective surface strategies is crucial for enhancing the electrochemical energy storage performance. Herein, a decoration technique for enhancing aesthetic appeal involves applying a metal-organic framework (Ni/Co-MOF) containing nickel and cobalt onto the inner walls of wood tracheids. The sequential modification steps include carbonization, oxidation activation, and acid-etching. The Ni/NiO/CoO-CW-4 electrode, made by acid-etching carbonized wood (CW) doped with nickel, nickel oxide, and cobalt oxide for 4 h, has excellent surface area and pore size distribution, high graphitization degree, and exceptional conductivity. Furthermore, surface modification optimizes the surface chemistry and phase composition, resulting in a 0.8 mm thick Ni/NiO/CoO-CW-4 electrode with an exceptionally high areal capacitance of 16.76 F cm-2 at 5 mA cm-2. Meanwhile, the fabricated solid-state supercapacitor achieves an impressive energy density of 0.67 mWh cm-2 (8.38 mWh cm-3) at 2.5 mW cm-2 (31.25 mW cm-3), surpassing representative modified wood-based carbon electrodes by approximately 2-7 times. Additionally, the supercapacitor demonstrates exceptional stability, maintaining 96.21 % of capacitance even over 10,000 cycles. The parameters presented here demonstrate a significant improvement compared to those typically observed in most modified wood-derived carbon-based supercapacitors, effectively addressing common issues of low energy density and suboptimal cycling performance with wood carbon composites.

Constructing high-throughput and highly adsorptive lithium-sulfur battery separator coatings based on three-dimensional hexagonal star-shaped MOF derivatives.

The electrochemical performance of high-performance lithium-sulfur (Li-S) batteries is affected by many factors such as shuttle effect and lithium dendrites. To effectively solve this problem, a hexagonal star-shaped composite catalyst containing Co-N-C active sites (Co-NC-X) has been rationally developed under the joint action of Zn2+ and Co2+ bimetallic ions. By modifying it to the Li-S battery separator, Co-NC-X can not only act as a physical barrier to effectively prevent the diffusion of lithium polysulfide (LiPS), but also the special morphology can expose more active sites and have a strong chemisorption effect on LiPS, which effectively promotes the redox conversion of LiPS and mitigates the shuttle effect. Li-S battery with Co-NC-X exhibits excellent electrochemical performance. It has a high specific capacity and stable cycling performance, with an initial discharge capacity of 1406.9 mAh·g-1 at 0.2 C and 876.8 mAh·g-1 at 2 C, and a lower capacity decline rate of 0.093 % for 500 cycles.

High-Valence Mn MOF Inspired by Laccase Mediators Enables Versatile Nature-Mimicking Catalysis.

In nature, active Mn3+ -ligand complexes produced by laccase catalyzed oxidation can act as the low-molecular mass, diffusible redox mediators to oxidize the phenolic substrates overcoming the limitations of natural enzymes. Learning from the metal-ligand coordination of natural functional units, high-valence Mn metal-organic framework (Mn MOF) is constructed to simulate the catalysis in natural mediator system. Benefiting from the characteristics of nanoscale size, rich metal coordination unsaturated sites, and mixed valence state dominated by Mn(III), Nano Mn(III)-TP exhibits superior laccase-mimicking activity, whose Vmax (maximal reaction rate) is much higher than that of natural laccase. Referring to natural systems, relevant free radical experiments prove that the material induces the production of active oxygen species with the assistance of carboxylic acid, and active oxygen species further oxidize phenolic substrates. Based on its robust performances, the primary oxidative degradation of an emerging pollutant triclosan (TCS) is creatively applied, an important antiasthmatic medicine terbutaline sulfate (TBT) detection, and the synthesis of non-toxic and black near-natural dyes for dyeing. By simulating the essential mediators of natural enzymatic catalysis, an Mn MOF-based material that demonstrates multiple novel applications is successfully developed, which introduces a new reliable strategy for achieving versatile nature-mimicking catalysis.

MOFs with the Stability for Practical Gas Adsorption Applications Require New Design Rules.

Metal-organic frameworks (MOFs) have been widely studied for their ability to capture and store greenhouse gases. However, most computational discovery efforts study hypothetical MOFs without consideration of their stability, limiting the practical application of novel materials. We overcome this limitation by screening hypothetical ultrastable MOFs that have predicted high thermal and activation stability, as judged by machine learning (ML) models trained on experimental measures of stability. We enhance this set by computing the bulk modulus as a measure of mechanical stability and filter 1102 mechanically robust hypothetical MOFs from a database of ultrastable MOFs (USMOF DB). Grand Canonical Monte Carlo simulations are then employed to predict the gas adsorption properties of these hypothetical MOFs, alongside a database of experimental MOFs. We identify privileged building blocks that lead MOFs in USMOF DB to show exceptional working capacities compared to the experimental MOFs. We interpret these differences by training ML models on CO2 and CH4 adsorption in these databases, showing how poor model transferability between data sets indicates that novel design rules can be derived from USMOF DB that would not have been gathered through assessment of structurally characterized MOFs. We identify geometric features and node chemistry that will enable the rational design of MOFs with enhanced gas adsorption properties in synthetically realizable MOFs.

Catalytically Active Site Mapping Realized through Energy Transfer Modeling.

The demands of a sustainable chemical industry are a driving force for the development of heterogeneous catalytic platforms exhibiting facile catalyst recovery, recycling, and resilience to diverse reaction conditions. Homogeneous-to-heterogeneous catalyst transitions can be realized through the integration of efficient homogeneous catalysts within porous matrices. Herein, we offer a versatile approach to understanding how guest distribution and evolution impact the catalytic performance of heterogeneous host-guest catalytic platforms by implementing the resonance energy transfer (RET) concept using fluorescent model systems mimicking the steric constraints of targeted catalysts. Using the RET-based methodology, we mapped condition-dependent guest (re)distribution within a porous support on the example of modular matrices such as metal-organic frameworks (MOFs). Furthermore, we correlate RET results performed on the model systems with the catalytic performance of two MOF-encapsulated catalysts used to promote CO2 hydrogenation and ring-closing metathesis. Guests are incorporated using aperture-opening encapsulation, and catalyst redistribution is not observed under practical reaction conditions, showcasing a pathway to advance catalyst recyclability in the case of host-guest platforms. These studies represent the first generalizable approach for mapping the guest distribution in heterogeneous host-guest catalytic systems, providing a foundation for predicting and tailoring the performance of catalysts integrated into various porous supports.

Effective synthesis and characterization of citric acid cross-linking of modified ferrous metal-organic framework and chitosan nanocomposite sponge for Th(IV) elimination: Adsorption isotherms, kinetic analysis, and optimization by Box-Behnken design.

This research presents a novel nanocomposite of ferrous metal-organic framework (Fe(II)-MOF) that has been encapsulated with chitosan matrix, leading to the development of a new adsorbent referred to as NH2-Fe(II)-MOF@CSC composite sponge. This composite sponge has shown effectiveness in removing radioactive thorium (IV) contamination from water sources. The adsorbent underwent characterization using techniques including FTIR, PXRD, BET analysis, and SEM. The adsorbent has a high surface area of 1360.8 m2/g. The most effective conditions for adsorbing Th(IV) were found to be a pH of 5, using 0.02 g of adsorbent dose per 25 mL, and maintaining a contact time of 100 min. The composite sponge demonstrated an impressive maximum adsorption capacity of 618.8 mg/g for Th(IV). The adsorption process was fitted to Langmuir isothermally and kinetically fitted to pseudo-second-order. Nonetheless, the relatively low adsorption energy of 6.22 kJ/mol suggests that the main adsorption mechanism is physisorption, which is marked by weaker van der Waals forces. This discovery could have implications for the material's potential for easy regeneration. In the analysis of the influence of temperature on the adsorption of Th(IV), it was discovered that the adsorption process is endothermic because the positive ΔHo value was 24.48 kJ.mol-1. Furthermore, a positive ΔSo value of 87.46 J.mol-1 K-1 suggests the existence of disorder at the solid-solution interface. Conversely, a temperature rise resulted in a higher negatively charged ΔGo, indicating that the adsorption process is spontaneous. The research also examined the mechanism of interaction, such as π-π interaction, hydrogen bonding, pore filling, and electrostatic interaction. It was noted that the adsorbent can be efficiently used for a maximum of six cycles, demonstrating its economic viability. The adsorption outcomes were optimized using the Box Behnken design (BBD).

Defect-Engineered MOF-801/Sodium Alginate Aerogel Beads for Boosting Adsorption of Pb(II).

Metal-organic frameworks (MOFs) are attractive adsorbents for heavy metal capture due to their superior stability, easy modification, and adjustable pore size. However, their inherent microporous structure poses challenges in achieving a higher adsorption capacity. Defect engineering is considered a simple method to create hierarchical MOFs with larger pores. Here, we employed l-aspartic acid as a mixed linker to bind Zr4+ clusters in competition with fumaric acid of MOF-801 to create defects, and the pore size was increased from 4.66 to 15.65 nm. Mercaptosuccinic acid was subsequently used as a postexchange ligand to graft the resultant MOF-801 by acid-ammonia condensation to further expand the pore size to 22.73 nm. Notably, the -NH2, -COOH, and -SH groups contributed by these two ligands increased the adsorption sites for Pb(II). The obtained defective MOF-801 with larger pores was thereafter loaded onto sodium alginate to form aerogel beads as adsorbents, and an adsorption capacity of 375.48 mg/g for Pb(II) was achieved, which is ∼51 times that of pristine MOF-801. The aerogel beads also exhibited outstanding reusability with a removal efficiency of ∼90.23% after 5 cycles of use. The adsorption mechanism of Pb(II) included ion-exchange interaction, as well as chelation interactions of Pb-O, Pb-NH2, and Pb-S. The versatile combination of defect engineering and composite beads provides novel inspirations for MOF modification for boosting heavy metal adsorption.

MOF Nanosheet-Functionalized Poly(lactic acid) Meta-membranes for Long-Term Air Purification and Intelligent Monitoring.

The wide use of conventional polymeric air filters is causing a dramatically increasing accumulation of plastic and microplastic pollution. The development of poly(lactic acid) (PLA) fibrous membranes for efficient air purification is of important significance but frequently challenged by the rapid decay of filtration performance due to the intrinsically poor electret properties of PLA. Here, we propose an electroactivity promotion methodology, involving the one-step synthesis and homogeneous incorporation of high-dielectric ZIF-8 nanosheets (ZIFNSs), to facilitate interfacial polarization and fiber refinement during electrospinning of PLA nanofibers. The preparative electrospun PLA/ZIFNS meta-membranes exhibited an unusual combination of significantly reduced nanofiber diameter (∼462 nm), enhanced surface potential (approaching 10 kV), and increased surface activity and facilitated the formation of electroactive phases. With well-controlled morphological features, the highly electroactive PLA/ZIFNS meta-membranes exhibited exceptional filtration efficiencies for PM2.5 and PM0.3 (99.2 and 96.0%, respectively) even at the highest airflow rate of 85 L/min, in clear contrast to that of its pure PLA counterpart (only 79.3 and 74.6%). Arising from the increased electroactivity and active contact sites, remarkable triboelectric performance and self-charging mechanisms were demonstrated for the PLA/ZIFNS meta-membranes, contributing to long-term efficient PM0.3 filtration (97.5% for over 360 min). Moreover, as triggered by physiological activities like respiration and speaking, the electroactive PLA/ZIFNS meta-membranes enabled real-time monitoring with high sensitivity and specificity. The proposed strategy affords significant promotion of electroactivity and triboelectric performance for PLA nanofibers, which may motivate the development of ecofriendly protective membranes for respiratory healthcare and real-time monitoring.