In situ growth of ZIF-8 nanoparticles on chitosan to form the hybrid nanocomposites for high-efficiency removal of Congo Red

Integration of STING activation and COX-2 inhibition via steric-hindrance effect tuned nanoreactors for cancer chemoimmunotherapy

Integrating immunotherapy with nanomaterials-based chemotherapy presents a promising avenue for amplifying antitumor outcomes. Nevertheless, the suppressive tumor immune microenvironment (TIME) and the upregulation of cyclooxygenase-2 (COX-2) induced by chemotherapy can hinder the efficacy of the chemoimmunotherapy. This study presents a TIME-reshaping strategy by developing a steric-hindrance effect tuned zinc-based metal-organic framework (MOF), designated as CZFNPs. This nanoreactor is engineered by in situ loading of the COX-2 inhibitor, C-phycocyanin (CPC), into the framework building blocks, while simultaneously weakening the stability of the MOF. Consequently, CZFNPs achieve rapid pH-responsive release of zinc ions (Zn2+) and CPC upon specific transport to tumor cells overexpressing folate receptors. Accordingly, Zn2+ can induce reactive oxygen species (ROS)-mediated cytotoxicity therapy while synchronize with mitochondrial DNA (mtDNA) release, which stimulates mtDNA/cGAS-STING pathway-mediated innate immunity. The CPC suppresses the chemotherapy-induced overexpression of COX-2, thus cooperatively reprogramming the suppressive TIME and boosting the antitumor immune response. In xenograft tumor models, the CZFNPs system effectively modulates STING and COX-2 expression, converting "cold" tumors into "hot" tumors, thereby resulting in ≈ 4-fold tumor regression relative to ZIF-8 treatment alone. This approach offers a potent strategy for enhancing the efficacy of combined nanomaterial-based chemotherapy and immunotherapy.

Improving the particulate matter filtration, antibacterial, and degradation properties of electrospinning poly(lactic acid) membranes with ZIF-8@chitosan

In order to improve the filtration efficiency of electrospinning poly(lactic acid) (PLA) membrane on particulate matter (PM), endow the membrane with good antibacterial properties, and accelerate the degradation effect of PLA materials in natural water and soil environments, ZIF-8@chitosan (ZIF-8@CS) was prepared by in situ growth method and was combined with PLA to manufacture the PLA/ZIF-8@CS electrospinning membranes. The PLA/ZIF-8@CS (3 wt%) membrane exhibited filtration efficiencies of 96.79 % for PM2.5 and 91.21 % for PM10, which were significantly higher than that of PP melt-blown cloth. Due to the inherently positive charge and the synergistic interaction between CS and ZIF-8, the antibacterial rates of PLA/ZIF-8@CS membranes were up to 100 % for E. coli and S. aureus after contact for 8 h. The addition of ZIF-8@CS in the membranes also influenced the degradation behavior of PLA/ZIF-8@CS membranes evidently.

Yolk-shell MOF-on-MOF hybrid solid-phase microextraction coatings for efficient enrichment and detection of pesticides: Structural regulation cause performance differences

Metal-organic frameworks (MOFs) based composites with different structure-activity relationships have been widely used in the field of organic pollutant adsorption and extraction. Here, two MOF-on-MOF composites with different structures (yolk-shell and core-shell) from homologous sources were prepared by a simple in-situ growth synthesis method and structural regulation. In order to verify the effect of composite structure on the extraction capacity, the adsorption performance of the yolk-shell structure (YS-NH2-UiO-66@CoZn-ZIF) and the core-shell structured (NH2-UiO-66@CoZn-ZIF) material were compared by using them as coating material of direct immersion solid-phase microextraction (DI-SPME) to enrich six pesticides in five matrices. The results showed that because of the unique hollow hierarchical structure, high specific surface area (930.68 m2 g-1), abundant and open active sites, and synergistic and complementary adsorption forces, YS-NH2-UiO-66@CoZn-ZIF composites had the maximum adsorption amount of 36.01-66.31 mg g-1 under the same experiment condition, which was 6.81%-34.26 % higher than that of NH2-UiO-66@CoZn-ZIF. In addition, the adsorption mechanism of the prepared materials was verified and elaborated through theoretical simulations and material characterization. Under the optimized conditions, the YS-NH2-UiO-66@CoZn-ZIF-coated SPME-HPLC-UV method had a wide linear range (0.241-500 μg L-1), a good linear correlation coefficient (R2 > 0.9988), a low detection limits (0.072-0.567 μg L-1, S/N = 3) and low quantification limits (0.241-1.891 μg L-1, S/N = 10). The relative standard deviations of individual fibers and different batches of fibers were 0.47-6.20 % and 0.22-2.48 %, respectively, and individual fibers could be recycled more than 104 times. This work provided a good synthetic route and comparative ideas for exploring the in-situ growth synthesis of yolk-shell composites with reasonable structure-activity relationships.

Stable production of hydrogen peroxide over zinc oxide @ zeolitic imidazolate Framework-8 composite catalysts

A promising method of producing hydrogen peroxide (H2O2) is the electrochemical two-electron water oxidation reaction (2e- WOR). In this process, it is important to design electrocatalysts that are both earth abundant and environmentally friendly, as well as offering high stability and production rates. The research of WOR catalysts, such as the extensively used transition metal oxides, is mainly focused on the modification of transition metal elements. Few studies pay attention to the protective heterostructure of metal oxides. Here, we demonstrate for the first time an organometallic skeleton protection strategy to develop highly stable WOR catalysts for H2O2 generation. Unlike the pure ZnO and zeolite imidazole framework-8 (ZIF-8) catalysts, ZnO@ZIF-8 enabled the production of hydrogen peroxide at high voltages. The experimental results demonstrate that the ZnO@ZIF-8 catalyst stably generates H2O2 even under a high voltage of 3.0 V vs. RHE, with a yield reaching 2845.819 μmolmin-1 g-1. ZnO@ZIF-8 shows a relatively low overpotential, with a current density of 10 mA cm-2 and an overpotential of 110 mV. The ZnO@ZIF-8 catalyst's maximal FE value was 4.72 %. Moreover, the ZnO@ZIF-8 catalyst exhibits remarkable durability even after an extended 60-hour stability test. Operando Raman and theoretic calculation analyses reveal that the metal-organic skeleton being encapsulated on the metal oxide surface synergizes with each other, not only expanding the electrochemical surface area, but also adjusting the catalyst metal sites' adsorption capacity. A novel approach to the modification of 2e- WOR metal oxide catalyst is presented in this work.

One-pot co-crystallized hexanal-loaded ZIF-8/quaternized chitosan film for temperature-responsive ethylene inhibition and climacteric fruit preservation

Controlling ethylene production and microbial infection are key factors to prolong the shelf life of climacteric fruit. Herein, a nanocomposite film, hexanal-loaded ZIF-8/CS (HZCF) with "nano-barrier" structure, was developed by a one-pot co-crystallized of ZIF-8 in situ growth on quaternized chitosan (CS) and encapsulation of hexanal into ZIF-8 via microporous adsorption. The resultant film realized the temperature responsive release of hexanal via the steric hindrance and hierarchical pore structure as "nano-barrier", which can inhibit ethylene production in climacteric fruit on demand. Based on this, the maximum ethylene inhibition rate of HZCF was up to 52.6 %. Meanwhile, the film exhibits excellent antibacterial, mechanical, UV resistance and water retention properties, by virtue of the functional synergy between ZIF-8 and CS. Contributed to the multifunctional features, HZCF prolonged the shelf life of banana and mango for at least 16 days, which is 8 days longer than that of control fruit. More strikingly, HZCF is washable and biodegradable, which is expected to replace non-degradable plastic film. Thus, this study provides a convenient novel approach to simplify the encapsulation of active molecule on metal-organic frameworks (MOFs), develops a packaging material for high-efficient freshness preservation, and helps to alleviate the survival crisis caused by food waste.

Fabrication and characterization of a Bi2O3-modified chitosan@ZIF-8 nanocomposite for enhanced drug loading-releasing efficacy

In this study, a simple novel hybrid mesoporous nanomaterial derived from a metal-organic framework (ZIF-8) and chitosan, which were coated on green bismuth oxide, has been successfully synthesized, characterized, and applied to investigate its dapsone loading-releasing capability in the aqueous media. This suggested nanocomposite showed promise for drug loading from water b using hydrogen bonds, pi-pi, and electrostatic interactions. Structural and morphological analyses were performed on the proposed green synthesized nanocomposite through scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, and thermogravimetric analysis. Various influencing parameters, including pH, nanocomposite dose, and contact time, were investigated to optimize the dapsone loading process. Utilizing the non-linear optimization methodology, the results show that dapsone-loading efficiency was >85 % for 50 mg.L-1 of dapsone drug. The optimum parameters for achieving maximal loading of dapsone drug were pH = 6.8, hybrid mesosphere dose = 2.6 mg.mL-1, and time = 53 min. Based on the release investigations, the dapsone-loaded nanocomposite was put into phosphate buffer saline, at pH = 7.4 and T = 37 °C, with a maximum efficiency of 93.9 after 24 h.

Application of three-dimensional material CZIF-8/CS-MS as adsorbents for the determination of plant growth regulators in Schisandra chinensis

In this study, we employed a melamine sponge (MS) as the skeleton material and utilized carbonized ZIF-8 (CZIF-8) and chitosan (CS) as the raw materials to prepare CZIF-8/CS-MS, a novel material featuring a three-dimensional interconnected porous network. The resulting CZIF-8/CS-MS material possesses a unique porous structure, significant specific surface area and abundant active sites. These characteristics make CZIF-8/CS-MS a promising absorbent for selective purification of plant growth regulators (PGRs) including 1-naphthlcetic acid (NAA), naphthoxyacetic acid (NOA), 4-chlorophenoxyacetic acid (4-CPA), 2,4-dichlorophenoxyacetic acid (2,4-D). After optimizing the extraction conditions, excellent linearity (r > 0.9994) was observed within a wide linear range of 1-100 ng/mL using ultra high performance liquid chromatography-tandem quadrupole mass spectrometry. The detection limits (LODs) and limits of quantification (LOQs) were found to be in the range of 0.013-0.154 ng/mL and 0.044-0.515 ng/mL, respectively. Additionally, the relative recovery of Schisandra chinensis fruit samples was determined to be 89.7-99.4 %, with a relative standard deviation (RSDs) of ≤ 8.4 % (n = 3). Compared to other methods, this approach offers a multitude of benefits, which include but are not limited to exceptional sensitivity, reduced sample volume requirements, low LODs, a comparable linear range, and high reproducibility. The findings of this study pave the way for exploring novel functionalized sponge columns, which leverage the integration of nano-sorbent materials and coating agents, for the purpose of analyzing PGRs within intricate matrix samples.

Enhancing bone scaffold interfacial reinforcement through in situ growth of metal-organic frameworks (MOFs) on strontium carbonate: Achieving high strength and osteoimmunomodulation

Bioceramics have been extensively used to improve osteogenesis of polymers because of their excellent bone-forming capabilities. However, the inadequate interfacial bonding between ceramics and polymers compromises their mechanical properties. In this study, zeolitic imidazolate framework-8 (ZIF-8) was grown in situ on strontium carbonate (SrCO3) to construct a core-shell SrCO3@ZIF-8, which was then added to poly-l-lactic acid (PLLA) to print a SrCO3@ZIF-8/PLLA composite scaffold using selective sintering technology. First, ZIF-8 characterized by its multiple organic ligands, forms a robust interface with PLLA. Second, SrCO3 characterized by its negative zeta potential in solution, exhibits the ability to adsorb positively charged zinc ions. This, in turn, promotes the in situ growth of ZIF-8 on SrCO3, eventually achieving perfect bonding between the second phase and the PLLA matrix. Our findings indicated that the composite scaffold exhibited the highest compressive strength (21.93 MPa) and significantly promoted the osteogenic differentiation of mouse mesenchymal stem cells. Moreover, the in vivo results established that the SrCO3@ZIF-8/PLLA scaffold significantly accelerated bone regeneration efficiency in rat femur defects. The prepared scaffold, with its favorable mechanical properties and osteogenic activity, shows considerable promise for applications in bone repair.

Hydrophilic Chitosan-Doped Composite Diaphragm Reducing Gas Permeation for Alkaline Water Electrolysis Producing Hydrogen

The present paper studied the chitosan-doped composite diaphragm by the phase exchange method with the objective of developing a composite diaphragm that complies with the alkaline water electrolysis requirements, as well as tested the electrolytic performance of the diaphragm in alkaline water electrolysis. The structure and morphology are characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The performance of chitosan-doped composite diaphragms was tested; CS3Z12 composite diaphragm with a low area resistance (0.20 Ω cm2), a high bubble point pressure (2.75 bar), and excellent electrochemical performance (current density of 650 mA cm-2 at 1.83 V) shows the best performance. Moreover, the performance of the synthesized composite diaphragm is significantly elevated compared to commercial diaphragms (Zirfon PERL), which is promising for practical application in alkaline electrolytic cells.

Poly(acrylic acid-co-2-acrylamido-2-methyl-1-propanesulfonic acid)-grafted chitosan hydrogels for effective adsorption and photocatalytic degradation of dyes

As a result of the growth of industrialization and urbanization, the water ecosystem is contaminated by various pollutants, including heavy metal ions and dyes. The use of low-cost and environmentally friendly dye adsorbents has been investigated. A hydrogel was fabricated via graft polymerization of acrylic acid (AA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) onto chitosan. The hydrogel was used as a dye adsorbent and support for a zinc oxide (ZnO) powder photocatalyst. The adsorption capacity of the bare hydrogel was greater towards cationic dyes than anionic dyes. Grafting P(AA-co-AMPS) exhibited a 23-time increase in adsorption capacity towards crystal violet (CV) compared to pristine chitosan. The effect of the AA-AMPS molar ratio on CV adsorption was studied. A hydrogel with an AA-AMPS ratio of 10 : 1 had the highest adsorption capacity towards CV in water, removing 91% of the dye in 12 h. The maximum adsorption capacity was 2023 mg g-1. The adsorption kinetics and isotherm were described by the pseudo-second-order model and the Langmuir model, respectively. ZnO particles were in situ synthesized within the 10 : 1 hydrogel to facilitate the recovery of the photocatalyst. The ZnO hydrogel composite could remove 95% and 92% of CV from solutions on the 1st and 2nd cycle, respectively. In addition, the hydrogel composite containing only 8.7 wt% of ZnO particles effectively degraded adsorbed CV under sunlight and could be reused without requiring a chemical regeneration or photocatalyst recovery procedure. This hydrogel composite is an effective dual-functional material for the adsorption and photodegradation of dye pollutants in wastewater.

Transition Metal Ion Doping on ZIF-8 Enhances the Electrochemical CO2 Reduction Reaction

The electrochemical reduction of CO2  to diverse value-added chemicals is a unique, environmentally friendly approach for curbing greenhouse gas emissions while addressing sluggish catalytic activity and low Faradaic efficiency (FE) of electrocatalysts. Here, zeolite-imidazolate-frameworks-8 (ZIF-8) containing various transition metal ions-Ni, Fe, and Cu-at varying concentrations upon doping are fabricated for the electrocatalytic CO2 reduction reaction (CO2 RR) to carbon monoxide (CO) without further processing. Atom coordination environments and theoretical electrocatalytic performance are scrutinized via X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations. Upon optimized Cu doping on ZIF-8, Cu0.5 Zn0.5 /ZIF-8 achieves a high partial current density of 11.57 mA cm-2 and maximum FE for CO of 88.5% at -1.0 V (versus RHE) with a stable catalytic activity over 6 h. Furthermore, the electron-rich sp2 C atom facilitates COOH* promotion after Cu doping of ZIF-8, leading to a local effect between the zinc-nitrogen (Zn-N4 ) and copper-nitrogen (Cu-N4 ) moieties. Additionally, the advanced CO2 RR pathway is illustrated from various perspectives, including the pre-H-covered state under the CO2 RR. The findings expand the pool of efficient metal-organic framework (MOF)-based CO2 RR catalysts, deeming them viable alternatives to conventional catalysts.

The use of chitosan-based composites for environmental remediation: A review

The presence of hazardous pollutants in water sources as a result of industrial activities is a major environmental challenge that impedes the availability of safe drinking water. Adsorptive and photocatalytic degradative removal of various pollutants in wastewater have been recognized as cost-effective and energy-efficient strategies. In addition to its biological activity, chitosan and its derivatives are considered as promising materials for the removal of various pollutants. The abundance of hydroxyl and amino groups in the chitosan macromolecular structure results in a variety of concurrent pollutant's adsorption mechanisms. Furthermore, adding chitosan to photocatalysts increases the mass transfer while decreasing both the band gap energy and the amount of intermediates produced during photocatalytic processes, improving the overall photocatalytic efficiency. Herein, we have reviewed the current design and preparation of chitosan and its composites, as well as their applications for the removal of various pollutants by adsorption and photocatalysis processes. Effects of operating variables such as the pH, catalyst mass, contact time, light wavelength, initial pollutant's concentration, and catalyst recyclability, are discussed. Various kinetic and isotherm models are presented to elucidate the rates, and mechanisms of pollutant's removal, onto chitosan-based composites, and several case studies are presented. Additionally, the antibacterial activity of chitosan-based composites has been discussed. This review aims to provide a comprehensive and up-to-date overview of the applications of chitosan-based composites in wastewater treatment and put forward new insights for the development of highly effective chitosan-based adsorbents and photocatalysts. Finally, the main challenges and future directions in the field are discussed.

Composite beads from chitosan and zeolitic imidazolate framework-8 for the adsorption and photocatalytic degradation of reactive red 141

This study describes the fabrication of composite beads comprising chitosan and zeolitic imidazolate framework-8 (ZIF-8) as a natural biodegradable dye adsorbent and support for ZnO photocatalyst. Chitosan beads were cross-linked with trisodium citrate dihydrate to enhance the adsorption capacity for the reactive red 141 dye (RR141). The ability was further improved by adding ZIF-8. The optimum loading was 2.5%, and the adsorption equilibrium was reached within 2 h. The maximum adsorption capacity of the composite beads was 6.51 mg g^-1 at pH 4 when an initial concentration of 1000 mg L^-1 was used. The pseudo-second-order kinetics model and the Langmuir isotherm model best described the adsorption process. The composite beads could also adsorb dyes like reactive black, Congo red, direct yellow, reactive orange, rhodamine B, crystal violet, and methylene blue (MB). Thermal stability was significantly improved after coating the surface of the 2.5% ZIF beads with a ZnO photocatalyst. After UV irradiation for 5 h, the photocatalytic beads containing 2.59 weight percent of ZnO could decolorize 99% of MB and 90% of RR141 dyes with a degradation rate of 0.6032 h^-1 and 0.3198 h^-1, respectively. Furthermore, the photocatalytic beads remained effective for at least ten consecutive cycles.

High strength, controlled release of curcumin-loaded ZIF-8/chitosan/zein film with excellence gas barrier and antibacterial activity for litchi preservation

Polysaccharide films containing protein additives have good application prospects in agriculture and food field. However, interfacial incompatibility between hydrophobic proteins and hydrophilic polymers remains a major technical challenge. In this work, the interfacial compatibility between hydrophobic zein and hydrophilic chitosan (CS) is improved by the chemical crosslinking between zinc ions of curcumin-loaded zeolitic imidazolate framework-8 (Cur-ZIF-8) with CS and zein. With the improvement of interface compatibility, the results show that the elongation at break and O₂ barrier property of synthesized Cur-ZIF-8/CS/Zein are 9.2 and 1.5 times higher than CS/Zein, respectively. And the Cur-ZIF-8/CS/Zein exhibits superior antibacterial and antioxidant properties as well. Importantly, Cur-ZIF-8/CS/Zein can also be used as an intelligent-responsive release platform for curcumin. As a result, Cur-ZIF-8/CS/Zein can keep the freshness and appearance of litchi at least 8 days longer than that of CS/Zein. Therefore, this study provides a novel method to improve the interfacial compatibility between hydrophobic proteins and hydrophilic polymers, and is expected to expand the application of protein/polymer composites in agriculture and food field.

Preparation of metal organic frameworks modified chitosan composite with high capacity for Hg(II) adsorption

In this study, a novel modified chitosan composite adsorbent (UNCS) was prepared by crosslinking between chitosan and metal organic frameworks (MOFs) material UiO-66-NH₂ using epichlorohydrin as crosslinker. The influence of the prepared conditions was investigated. The structure and morphology of the composite were characterized by FT-IR, XRD, SEM, TGA, BET and zeta potential analysis. Effects of different variables for adsorption of Hg(II) on this adsorbent were explored. The kinetic studies indicated that the adsorption process followed the pseudo-second-order kinetic model and the adsorption equilibrium could be reached within 2 h. The adsorption was mainly controlled by chemical process. Adsorption isothermal studies illustrated that the adsorption fitted Langmuir isotherm model, implying the homogeneous adsorption on the surface of the adsorbent. The adsorbent exhibited high uptake and the maximum capacity from Langmuir model could reach 896.8 mg g^-1 at pH 6. Thermodynamic studies showed the spontaneous nature and exothermic nature of the adsorption process. Additionally, the removal of Hg(II) on UNCS could achieve over 90 %. The adsorption-desorption cycled experiments indicated the appropriate reusability of the adsorbent. Hence, this adsorbent would be promising for the removal of Hg(II) from wastewater.

Efficient adsorption of Congo red by micro/nano MIL-88A (Fe, Al, Fe-Al)/chitosan composite sponge: Preparation, characterization, and adsorption mechanism

MIL-88A crystals with three different metal ligands (Fe, Al, FeAl) were prepared by hydrothermal method for the first time. The three materials' crystal structure and surface morphology are different, leading to different adsorption properties of Congo red (CR). The maximum adsorption capacities of MIL-88A (Fe), MIL-88A (FeAl), and MIL-88A (Al) are 607.7 mg · g^-1, 536.4 mg · g^-1, and 512.1 mg · g^-1 respectively. In addition, MIL-88A was combined with chitosan (CS) respectively, and MIL-88A/CS composite sponge was prepared by the freeze-drying method, which not only solved the defect that MIL-88A powder was difficult to recover but also further improved the removal ability of CR by the adsorbent. The maximum adsorption capacities of MIL-88A (FeAl)/CS, MIL-88A (Fe)/CS, MIL-88A (Al)/CS, and CS are 1312 mg · g^-1, 1056 mg · g^-1, 996.7 mg · g^-1, and 769.6 mg · g^-1, respectively. The structure and physicochemical properties of the materials were analyzed by SEM, FTIR, XRD, TGA, BET, and Zeta. The adsorption process of CR follows pseudo-second-order kinetics and Langmuir, Sips isotherm model. Combined with thermodynamic parameters, the adsorption behavior was described as endothermic monomolecular chemical adsorption. The removal of CR is attributed to electrostatic interactions, hydrogen bonding, metal coordination effects, and size-matching effects.

Treatment of fluorinated wastewater with chitosan modified activated sludge lysis ash

Preparation of a novel environmentally friendly and cost-effective composite adsorbent for fluoride removal is presented in this work. An activated sludge lysis ash/chitosan (ASLA/C) composite adsorbent was synthesised using an in situ coprecipitation method, and the removal effect of the material was analysed by static adsorption, isothermal adsorption and kinetic adsorption tests. Langmuir model could better describe the adsorption process and the adsorption was in accordance with the kinetic equation of the pseudo-second-order kinetics reaction. The values of adsorption thermodynamic and kinetic parameters were indicated that the adsorption of fluoride ions is a spontaneous, heat-absorbing entropic process, and the reaction was carried out by a combination of mechanisms, such as electrostatic adsorption, ion exchange, surface complexation and hydrogen bonding. The experimental results indicated that ASLA/C can be used as a cheap and readily available alternative efficient adsorbent where the maximum fluorinate absorption was observed with 7.714 mg g^-1, while solving the problem of waste from activated sludge lysis disposal and realizing the environmental benefits of waste.

ZIF-8 metal organic framework materials as a superb platform for the removal and photocatalytic degradation of organic pollutants: a review

Metal organic frameworks (MOFs) are attracting significant attention for applications including adsorption, chemical sensing, gas separation, photocatalysis, electrocatalysis and catalysis. In particular, zeolitic imidazolate framework 8 (ZIF-8), which is composed of zinc ions and imidazolate ligands, have been applied in different areas of catalysis due to its outstanding structural and textural properties. It possesses a highly porous structure and chemical and thermal stability under varying reaction conditions. When used alone in the reaction medium, the ZIF-8 particles tend to agglomerate, which inhibits their removal efficiency and selectivity. This results in their mediocre reusability and separation from aqueous conditions. Thus, to overcome these drawbacks, several well-designed ZIF-8 structures have emerged by forming composites and heterostructures and doping. This review focuses on the recent advances on the use of ZIF-8 structures (doping, composites, heterostructures, etc.) in the removal and photodegradation of persistent organic pollutants. We focus on the adsorption and photocatalysis of three main organic pollutants (methylene blue, rhodamine B, and malachite green). Finally, the key challenges, prospects and future directions are outlined to give insights into game-changing breakthroughs in this area.

Historical development and prospect of intimately coupling photocatalysis and biological technology for pollutant treatment in sewage: A review

Through the synergistic effect of photocatalysis and biodegradation, intimately coupling photocatalysis and biological (ICPB) technology could improve the removal rate and mineralization rate of refractory pollutants and reduce the toxicity of intermediate products. ICPB system was characterized with the advantages of simple operation, low energy consumption and high treatment efficiency. As a new sewage treatment technology, ICPB system has shown great potential in the treatment of refractory pollutants, and has been widely concerned. In this study, the research progress of photocatalyst, carrier and biofilm in ICPB system were discussed, and the degradation mechanism was introduced. The shortcomings of the current ICPB system were pointed out, and the possible research directions of ICPB in the future were proposed. This review aimed to deepen the understanding of ICPB technology and promoted the further development of ICPB technology in the treatment of refractory pollutants.

Rapid degradation of Congo red wastewater by Rhodopseudomonas palustris intimately coupled carbon nanotube - Silver modified titanium dioxide photocatalytic composite with sodium alginate

With a large number of Congo red used in textiles, Congo red wastewater was not easily degraded, resulting in environmental and health-related problems. In order to improve the degradation efficiency of Congo red wastewater, A novel intimately coupled photocatalysis and biodegradation (ICPB) system was prepared by coupling Rhodopseudomonas palustris (R. Palustris), carbon nanotube - silver modified titanium dioxide photocatalytic composite (CNT-Ag -TiO₂, CAT) and sodium alginate (SA) (R. palustris/CAT@SA). Compared with immobilized CAT and R. palustris, the R. palustris/CAT@SA improved the degradation and removal rates of Congo red by 14.3% and 42.1%, and the COD removal rates by 76% and 44.6%, respectively. The mechanism of the degradation of Congo red by the new ICPB was that the Congo red on the surface of the support was degraded into long-chain alkanes by the superoxide and hydroxyl radicals of CAT product, and then the long-chain alkanes were completely mineralization by R. Palustris, which reduced the accumulation of intermediates in the photocatalysis. Most of the Congo red was adsorbed to the interior of the carrier was degraded into aromatic hydrocarbons by R. Palustris, and then oxidized and degraded by CAT, and a small part of the Congo red would be directly mineralized by R. Palustris. A novel technical solution of R. palustris/CAT@SA provided a potential application to the degradation of dye wastewater.

Applications of nanocomposites based on zeolitic imidazolate framework-8 in photodynamic and synergistic anti-tumor therapy

Due to the limitations resulting from hypoxia and the self-aggregation of photosensitizers, photodynamic therapy (PDT) has not been applied clinically to treat most types of solid tumors. Zeolitic imidazolate framework-8 (ZIF-8) is a common metal-organic framework that has ultra-high porosity, an adjustable structure, good biocompatibility, and pH-induced biodegradability. In this review, we summarize the applications of ZIF-8 and its derivatives in PDT. This review is divided into two parts. In the first part, we summarize progress in the application of ZIF-8 to enhance PDT and realize theranostics. We discuss the use of ZIF-8 to avoid the self-aggregation of photosensitizers, alleviate hypoxia, increase the PDT penetration depth, and combine PDT with multi-modal imaging. In the second part, we summarize how ZIF-8 can achieve synergistic PDT with other anti-tumor therapies, including chemotherapy, photothermal therapy, chemodynamic therapy, starvation therapy, protein therapy, gene therapy, and immunotherapy. Finally, we highlight the challenges that must be overcome for ZIF-8 to be widely applied in PDT. To the best of our knowledge, this is the first review of ZIF-8-based nanoplatforms for PDT.

Using recycled coffee grounds for the synthesis of ZIF-8@BC to remove Congo red in water

Around 6.6 million tons of spent coffee is produced per year, resulting in resources loss and potential environmental risks. Hence, a green technique is required to reuse the spent coffee grains. In this study, coffee grounds were burnt at 900 °C to generate the biochar (BC) for the synthesis of the porous adsorbent (ZIF-8 @BC) by growing ZIF-8 on the surface of BC. We applied the well-prepared ZIF-8 @BC to remove Congo red (CR) in water. The maximum adsorption capacity of ZIF-8 @BC on Congo red in water was up to 1080.4 mg/g, which was significantly higher than that of many different types of BCs reported in previous studies. The reasons for its highly efficient adsorption of CR probably was attributed to metal ions and coordinatively unsaturated sites in the material. Also, BC enabled the less aggregation of ZIF-8 to provide sufficient specific surface area for CR adsorption. From the analysis of the pseudo-second-order kinetic model and Langmuir model, the adsorption of ZIF-8 @BC on CR was a homogeneously chemical adsorption process regulated by electrostatic interaction, π-π stacking and metal coordination.

Exploiting the Fracture in Metal-Organic Frameworks: A General Strategy for Bifunctional Atom-Precise Nanocluster/ZIF-8(300 °C) Composites

Atom-precise nanoclusters-metal-organic framework (APNC/MOF) composites, as bifunctional material with well-defined structures, have attracted considerable attention in recent years. Despite the progress made to date, there is an urgent need to develop a generic and scalable approach for all APNCs. Herein, the authors present the Exploiting Fracture Strategy (EFS) and successfully construct a super-stable bifunctional APNC/ZIF-8(300 °C) composite overcoming the limitations of previous strategies in selecting APNCs. The EFS utilizes the fracture of ZnN in ZIF-8 after annealing at 300 °C. This method is suitable for all kinds of S/P protected APNCs with different sizes, including uncharged clusters Au₁ Ag₃₉ , Ag₄₀ , negatively charged Au₁₂ Ag₃₂ , positively charged Ag₄₆ Au₂₄ , Au₄ Cu₄ and P-ligand-protected Pd₃ Cl. Importantly, the generated APNC/MOF show significantly improved performances, for example, the activities of Au₁₂ Ag₃₂ /ZIF-8(300°C), Au₄ Cu₄ /ZIF-8(300°C), and Au₁ Ag₃₉ /ZIF-8(300°C) in the corresponding reactions are higher than those of Au₁₂ Ag₃₂ , Au₄ Cu₄ , and Au₁ Ag₃₉ , respectively. In particular, Au₁₂ Ag₃₂ /ZIF-8(300 °C) shows higher activity than Au₁₂ Ag₃₂ @ZIF-8. Therefore, this work offers guidance for the design of bifunctional APNC/MOF composites with excellent optimization of properties and opens up new horizons for future related nanomaterial studies and nanocatalyst designs.

Enhanced performance of photocatalytic treatment of Congo red wastewater by CNTs-Ag-modified TiO2 under visible light

In order to improve the treatment efficiency of printing and dyeing wastewater, the carbon nanotubes-silver-modified-titanium dioxide (CNTs-Ag-TiO₂, CAT) ternary composite was prepared by a mechanical mixing method. It was found that the morphology of the prepared CAT sample was uniformly coated with strips of CNTs, speckled Ag, and lumpy TiO₂. The (002) crystal plane of CNTs, the (101) crystal plane of TiO₂, and the (111) crystal plane of Ag were observed, which possessed functional groups such as Ti-OH and Ti-O-C, indicating that the prepared CAT sample had photocatalytic reaction sites. The visible light utilization of titanium dioxide can be improved. The treatment effect of different proportions of CNTs-Ag-TiO₂ on Congo red wastewater was tested, and the results showed that the optimum degradation effect of Congo red wastewater was CNTs: Ag = 10:1, and the doped amount of CNTs/Ag was 15%, and the removal rate of Congo red wastewater could reach 100% within 140 min. The excellent removal effect of CAT ternary composite on Congo red wastewater provided a new idea and way for the modification of TiO₂ and its composites for the potential of organic dyes degradation.

Adsorption of Congo red and tetracycline onto water treatment sludge biochar: characterisation, kinetic, equilibrium and thermodynamic study

In this study, readily available inexpensive water treatment sludge (WTS) was used to prepare adsorbent for the removal of Congo red (CR) and tetracycline (TC) from aqueous solutions. The structural characteristics and adsorption properties of WTS biochar were characterised via scanning electron microscope, energy dispersive X-ray spectroscopy, Brunauer-Emmett-Teller and Fourier Transform infrared spectroscopy. In batch experiments, the adsorption factors, kinetics, isothermal curves and thermodynamics of the adsorption properties were investigated. The optimum preparation condition of WTS biochar was 400 °C for 4 h under O₂-limited pyrolysis, which exhibited increased specific surface area and pore structures. The best adsorption was observed when the pH of the CR and TC solutions was 7 and 4, respectively. The adsorption process followed the pseudo-second-order model, indicating that the main control step was the chemical adsorption process. Isotherm data were best described by the Langmuir model, and the maximum adsorption capacities for CR and TC were 116.4 and 58.5 mg·g^-1, respectively. Thermodynamic parameters revealed that the adsorption process was spontaneous and endothermic. According to the analysis, the adsorption mechanism of CR could be attributed to electrostatic attraction, π-π conjugation and hydrogen bonding, whereas that of TC was potentially associated with cation exchange, complex precipitation, π-π conjugation and hydrogen bonding.

Zeolitic imidazolate framework-8 as a dispersive solid phase extraction sorbent for simultaneous determination of 145 pesticide residues in polyphenol-rich plants

Many plants showed higher polyphenol content, which caused the matrix effect and made the analysis of trace pesticide residues highly challenging. A common approach to improving matrix effects is to purify pesticides through the use of sorbents, but this requires a combination of multiple sorbents and extensive use. Zeolitic imidazolate framework-8 is widely used for pesticide analysis due to its high porosity, large specific surface area and versatility. Here, We established and validated a modified quick, easy, cheap, effective, rugged, and safe method based on a zeolitic imidazolate framework-8 that was used to test the removal ability for polyphenols. And 145 pesticide residues in peppermint, perilla, fennel, and mulberry leaves were analyzed by the modified method coupled with LC-MS/MS. The mean recoveries of all pesticide residues were in the range of 74.3%-103.7%, with mean relative standard deviations≤ 9.1% at spiked concentrations of 1, 10, 50, and 100 μg kg^-1 for mulberry leaves. The limits of quantitation of the method ranged from 1 to 50 μg kg^-1 . This study offers a reliable approach for the accurate quantitative analysis of various trace substances in the polyphenol-rich plants. This article is protected by copyright. All rights reserved.

Metal-organic framework grown in situ on chitosan microspheres as robust host of palladium for heterogeneous catalysis: Suzuki reaction and the p-nitrophenol reduction

In this study, the metal-organic framework ZIF-8 has been successfully planted on the surface of chitosan microspheres (CS/PDA@ZIF-8) using polydopamine as connecting material for the first time, which avoids the use of expensive, non-renewable, and non-biodegradable polystyrene microspheres commonly used as templates to prepare core-shell structures. Moreover, the metal-organic framework ZIF-8 was prepared specially by three different methods and all characterized by SEM, TEM, and BET, and the ZIF-8 shell prepared at room temperature presents a regular morphology, uniform size, large specific surface area (353.1 m²/g) than the shells prepared by the other methods including. The CS/PDA@ZIF-8₂₅@Pd with high catalytic activity and high stability was especially prepared by encapsulating Pd nanoparticles into the pores of CS/PDA@ZIF-8₂₅. Notably, the fabricated catalyst performed well in an array of reactions, for example the Kapp value of the p-nitrophenol reduction reaction reached 0.0426 s^-1, and the TOF of the Suzuki coupling reaction reached 128 h^-1. In addition, the ZIF-67, UiO-66, UiO-66-NH₂, HKUST-1, and NH₂-MIL-53(Al) were also grown on chitosan microcapsules successively to prepare the core-shell microspheres, which prove the universal applicability of this strategy. And beyond that, the introduction of chitosan microspheres endows the material with biodegradable properties and excellent recycling properties.

Antibacterial Zeolite Imidazole Frameworks with Manganese Doping for Immunomodulation to Accelerate Infected Wound Healing

Numerous nanomedicines currently emerge to reduce the dramatic threat in antibiotics resistance for antibacterial application against severe bacterial infections, while it is restricted by over-reacted immune response to pathogenic bacteria. Herein, enzymatic activity is introduced into the zeolitic imidazolate framework-8 (ZIF-8) to achieve sterilization by releasing Zn ions, as well as inflammation regulation through the variable valence of Mn ions that are uniformly doped into its framework. Within this simple metal organic framework (MOF) structure design, Mn-ZIF-8 possesses the co-existence of Mn²⁺ /Mn⁴⁺ to endow the nanocomposite with the anti-inflammatory capabilities, which can be adjusted through the redox environment. The enzymatic activity of Mn ions and superiority of pore structure of ZIF-8 are effectively combined to realize the substrate selection via reactant molecular size and high-efficiency internal catalytic performance. By such design, this nanocomposite would not only exhibit an excellent antibacterial performance against pathogenic bacteria, but also reshape the inflammatory immunity by regulating macrophage polarization to suppress over-reacted inflammation, leading to a favorably therapeutic efficiency on bacteria-infected wound healing in animal models. Taken together, this nanoplatform provides effective approach for accelerating infected wound healing via bacteria killing and inflammation modulation, and may be extended for the therapy of other severe bacteria-induced infections.

In situ growth zeolite imidazole framework materials on chitosan for greatly enhanced antibacterial effect

Zeolite imidazole framework materials (ZIFs) are a new type of antibacterial material with high chemical and thermal stability, and good antibacterial effect. However, powder ZIFs materials have the disadvantages of difficult separation and easy aggregation, which limit their application. In this work, ZIFs and chitosan (CS) were compounded by in-situ growth method to prepare a new antibacterial agent. The synergism of CS and ZIFs can effectively promote antibacterial effect compared with CS and pristine ZIFs, and CS/ZIF-67(1:6) has the best antibacterial activity, and its inhibitory rate (in 15 h) of E. coli is 96.75%, and the inhibitory rate of S. aureus reaches as high as 100%. This composites can effectively cause bacterial cell membrane rupture and leakage of internal nucleic acid and protein, leads to achieve antibacterial effect, and also exhibit excellent long-term (at least 5 days) antibacterial properties, the leaching of cobalt is below than 0.5 mg·L^-1, and this composites are with excellent bio-compatibility.

Adsorption of REEs from Aqueous Solution by EDTA-Chitosan Modified with Zeolite Imidazole Framework (ZIF-8)

Chitosan (CS) modified with ethylenediamine tetraacetic acid (EDTA) was further modified with the zeolite imidazole framework (ZIF-8) by in situ growth method and was employed as adsorbent for the removal of rare-earth elements (REEs). The material (EDTA-CS@ZIF-8) and ZIF-8 and CS were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and nitrogen adsorption/desorption experiments (N2- Brunauer-Emmet-Teller (BET)). The effects of adsorbent dosage, temperature, the pH of the aqueous solution, contact time on the adsorption of REEs (La(III), Eu(III), and Yb(III)) by EDTA-CS@ZIF-8 were studied. Typical adsorption isotherms (Langmuir, Freundlich, and Dubinin-Radushkevich (D-R)) were determined for the adsorption process, and the maximal adsorption capacity was estimated as 256.4 mg g-1 for La(III), 270.3 mg g-1 for Eu(III), and 294.1 mg g-1 for Yb(III). The adsorption kinetics results were consistent with the pseudo-second-order equation, indicating that the adsorption process was mainly chemical adsorption. The influence of competing ions on REE adsorption was also investigated. After multiple cycles of adsorption/desorption behavior, EDTA-CS@ZIF-8 still maintained high adsorption capacity for REEs. As a result, EDTA-CS@ZIF-8 possessed good adsorption properties such as stability and reusability, which have potential application in wastewater treatment.

DETA impregnated attapulgite hybrid ZIF-8 composite as an adsorbent for the adsorption of aspirin and ibuprofen in aqueous solution

The diethylenetriamine (DETA) impregnated modified attapulgite hybrid ZIF-8 composite is a new type of amine impregnated hybrid MOF adsorbent, which has an excellent ability to remove aspirin and ibuprofen from aqueous solution.

Synthesis of Fe3O4@chitosan@ZIF-8 towards removal of malachite green from aqueous solution: Theoretical and experimental studies

Discharges of dyes-containing wastewater from industries have created global concern. Removal of these substances from aqueous solution is very important and essential. Magnetic chitosan coated with ZIF-8 was prepared successfully and used to eliminate cationic dye malachite green in various conditions. To find the effectiveness of ZIF-8 towards malachite green removal, their surface interaction was investigated using density functional theory (DFT) calculations for the first time which the results show physisorption of malachite green on ZIF-8. The characteristics of adsorbent synthesized were evaluated using XRD, FTIR, FE-SEM, TEM and TGA analysis. In addition, the influence of different parameters on malachite green removal was investigated. The results showed that pH = 7, 40 mg of adsorbent dosage, 10 mg/L initial concentration, 40 min contact time and temperature of 25 °C were obtained as an optimum values for Fe₃O₄@chitosan@ZIF-8. The equilibrium data were in good agreement with the Langmuir model having maximum capacity (q_m) value of 3.282 mg/g. The experimental data revealed that the adsorption process obeyed to pseudo-second order kinetic model. It was concluded that Fe₃O₄@chitosan@ZIF-8 can be utilized as an efficient and effective adsorbent for removal of toxic malachite green dye from aqueous solution.

A mechanistic insight into the rapid and selective removal of Congo Red by an amide functionalised Zn(ii) coordination polymer

New CPs [Zn(μ-1κOO':2κN-L)(H₂O)(BDC)_0.5]_n·n(DMF) (1), [Cd(μ-1κO:2κN-L)₂(H₂O)₂]_n (2), and [Pb(μ-1κOO':2κO'-L)(μ-1κO:2κO':3κN-L)]_n (3) [L = 4-(pyridin-3-ylcarbamoyl)benzoate; BDC = benzene-1,4-dicarboxylate] were synthesized and characterized by elemental, FT-IR, powder, and single-crystal X-ray diffraction analyses. Single crystal X-ray diffraction analysis discloses 1D polymeric architectures for 1 and 2 and a 2D one for 3. The topological analysis exemplifies a 2,2,3-connected 3-nodal net with the point symbol {8²·12}₂{8}₃ for 1, a 2,4-connected bimodal net for 2, and a 3,4,7-connected trinodal net for 3. CP 1 shows a selective removal of the Congo Red (CR) dye amongst various dyes. It can be recycled and reused without any significant loss of its dye removal efficiency. An insight into the selective removal of the Congo dye is provided by in silico studies, being accounted for by anion-π, cation-π, and π-π stacking interactions, involving the Zn(ii) ion, phenyl rings, and O_carboxylate of L, and the phenyl rings, naphthalene rings, and O_sulfonate of CR.

Enhanced chemical sensing for Cu2+ based on composites of ZIF-8 with small molecules

Two organic molecules, pyridoxal hydrazide (PAH) and salicylaldehyde based Rhodamine B hydrazone (RBS) were integrated into zeolitic imidazolate framework-8 (ZIF-8) to give composites, namely PAH/ZIF-8 and RBS/ZIF-8. The organic molecules and ZIF-8 are proposed to be assembled via hydrogen bonds and π–π stacking in the composites. The mass fraction of PAH and RBS in the composites was calculated to be 21.86% and 29.3%. The fluorescence of PAH/ZIF-8 is quenched regularly by Cu²⁺. The detection limit for Cu²⁺ was calculated to be 1.42 nM for PAH/ZIF-8, which is one order of magnitude lower than that of PAH. The detection limit for Cu²⁺ was determined to be 0.8 μM for RBS/ZIF-8, which is three times lower than that of RBS. The two composites both display high selectivity to Cu²⁺ over competing metal ions. The PAH/ZIF-8 fluorescent sensor was successfully applied to Cu²⁺ determination in environmental water. PAH/ZIF-8 exhibits excellent cell membrane permeability and low cytotoxicity in cellular imaging. The enhanced chemical sensor was designed by introducing small molecules into ZIF-8 for the specific recognition of Cu²⁺.

An enhanced chemical sensor was designed by introducing small molecules into ZIF-8 for the specific recognition of Cu²⁺.

Reusable ZIF-8@chitosan sponge for the efficient and selective removal of congo red

A light ZIF-8@chitosan sponge was prepared by an in situ method for the efficient and selective removal of congo red from aqueous solution.