Facile fabrication of hierarchical porous ZIF-8 for enhanced adsorption of antibiotics

Fluorescence sensing probe based on functionalized mesoporous MOFs for non-invasive and detection of dopamine in human fluids

Abnormal amount of dopamine (DA) in human body is closely relate to various diseases, such as Parkinson's disease, pheochromocytoma. Real-time monitoring DA is crucial for disease warning, diagnosis and treatment. Currently, most methods rely on invasive blood testing for detecting DA, which is only completed with the aid of the medical staffs in hospitals. Herein, a non-invasive fluorescence visual strategy is developed for the real-time monitoring DA, based on luminescent nanoparticles and modified mesoporous zeolite imidazole framework (ZIF-8-NH2) dodecahedrons. During the reaction process, DA is enriched through the spatial configuration of ZIF-8-NH2 and hydrogen bonding effect. The luminescence of Cr3+-doped zinc gallate (ZnGa2O4:Cr3+, ZGC) is inhibited by the photo-induced electron transfer (PET) mechanism to realize sensitively detecting DA. The intelligent sensing platform based on the designed fluorescence probe and color recognition system is structured for real-time detection of DA in urine. Furthermore, a skin-fitting hydrogel patch is prepared by combining a fluorescent probe with chitosan, which enables sensitive and accurate detection of DA in sweat without the complex sample pretreatment. The non-invasive fluorescence detection method provides an effective strategy for quantitatively monitoring DA in human fluids.

Synthesis of a novel cost-effective double-ligand Zr-based MOF via an inverted modulator strategy towards enhanced adsorption and photodegradation of tetracycline

Developing visible-light response photocatalysts with high activity and adsorption alongside sustainability is vitally important to environmental restoration. Here, we fabricated a novel metal organic framework (MOF) with cost-effective double-ligands (fumaric acid and 2-aminoterephthalic acid as ligand precursors, denoted as MA-MOF) via a facile solvothermal method. Specifically, crystalline [Zr6O4(OH)4(fumarate)6] (MOF-801) can be only formed with monocarboxylic acids as modulators. Therefore, in the construction of crystalline double-ligand MA-MOF, the absence of monocarboxylic acid modulators successfully prevents the formation of crystalline MOF-801. Instead, the crystalline double-ligand MA-MOF is formed. Properties of MA-MOFs including the surface area, porosity, charge transfer resistance, and energy level position can be adjusted via altering the ratio of ligands. The optimal sample, MA-MOF2 (prepared with a molar ratio of fumaric acid and 2-aminoterephthalic acid being 2:1), shows a total 94.6% removal of tetracycline via adsorption and photodegradation, far exceeding the corresponding single-ligand counterparts. This work proposes an innovative inverted modulator strategy for constructing double-ligand MOFs.

Synthesis of LDH-MgAl and LDH-MgFe composites for the efficient removal of the antibiotic from water

In this study, novel lamellar double hydroxide composites (LDH-MgAl and LDH-MgFe) were synthesized at different metal salt ratios (1:1 to 3:1) and fully characterized using various techniques such as XRD, FTIR, SEM, EDS, and TGA. The resulting LDHs demonstrated a high affinity for efficiently removing tetracycline (TC) antibiotic from water, particularly at a moderate molar ratio of 3:1. This ratio exhibited improved structural characteristics, resulting in better TC uptake from water. The improved performance was supported by the increased abundance of surface functional groups (OH, NO3, CO32-, C-O-C, Fe-O, and Al-O-Al). The TGA analysis established the high stability of the LDHs when subjected to high temperatures. The kinetics of TC adsorption onto LDH fitted with the PSO (R2 = 0.935-0.994) and Avrami (R2 = 0.9528-0.9824) models, while the equilibrium data fitted the Liu and Langmuir isotherm models, with maximum monolayer adsorption capacities of 101.1 mg g-1 and 70.83 mg g-1, respectively-significantly higher than many reported values in the literature. The positive values of ΔH0 and ΔS0 indicate an endothermic process, with TC removal mechanisms influenced by physical interactions, such as hydrogen bonding, electrostatic interaction, and π-cation with the surface functional groups of the LDH adsorbents. These results suggest that LDH-MgAl and LDH-MgFe are promising adsorbents for the removal of TC from water.

Simultaneous size and defect control of metal-organic framework by deep eutectic solvent for efficient perfluoroalkyl substances adsorption: Delving into mechanism

This study reports an environment-friendly protocol to prepare a metal-organic framework (MOF) with simultaneously controlled particle size and open metal site for adsorption removal of perfluoroalkyl substances (PFASs). The successful preparation of UiO-66 with defect and crystal size modulation was achieved using a green and straightforward method, adjusting the components and molar ratios of ammonium salt/glycolic acid deep eutectic solvents (DESs). The corresponding modulation mechanism primarily relied on the combined regulation of the deprotonation and competitive coordination abilities of the eutectic solvent components. The adsorption process was thoroughly examined using spectral analyses, adsorption behavior profiling, and ab initio molecular dynamics simulations. The results revealed that PFAS adsorption is driven by combined capturing effects, such as CF-π, acid/base coordination, C-F⋯Zr, hydrogen bonding, and hydrophobic interactions. Our findings were not thus that the smaller the crystal size of MOF and the higher the defect concentration in the material, the better the PFAS adsorption performance. The result demonstrated the combined effect of these adsorbent features on PFAS mixtures. Furthermore, they revealed unique differences in sorption properties between these targets with different carbon chain lengths. Extensive defects in DES-based UiO-66 led to larger pores, increasing the availability of many adsorption sites and aiding in PFAS adsorption and diffusion. Nevertheless, the surplus of larger pores in the substance increased the competitive adsorption, reducing the total quantity of PFASs absorbed. Furthermore, various interactions and a less restrictive configuration increased the contact of functional groups with adsorbates, substantially enhancing the adsorption. This study investigates the basic questions about how PFAS molecules are adsorbed on DES-based MOFs and the relationship among the structure, properties, and performance to improve the efficiency of this novel adsorbent.

Sulfate Radical-Based Degradation of Organic Pollutants: A Review on Application of Metal-Organic Frameworks as Catalysts

The degradation of organic pollutants present in domestic and industrial effluents is a matter of concern because of their high persistence and ecotoxicity. Recently, advanced oxidation processes (AOPs) are being emphasized for organic pollutant removal from effluents, as they have shown higher degradation efficiencies when compared to conventional activated sludge processes. Sulfate radical-based methods are some of the AOPs, mainly carried out using persulfate (PS) and peroxymonosulfate (PMS), which have gained attention due to the ease of sulfate radical generation and the effective degradation of organic molecules. PMS is gaining more popularity because of its high reactivity and ability to generate excess sulfate radicals. PMS has been the major focus; therefore, its mechanism has been explained, and limitations have been elaborated. The involvement of metal-organic frameworks for PMS/PS activation applied to organic pollutant removal and recent advances in the application of biochar and hydrogel-assisted metal-organic frameworks have been discussed.

Hierarchical porous zeolitic imidazolate framework‑8 supported hollow-fiber liquid-phase microextraction of nine typical phenolic pollutants in water samples followed by electrophoretic analysis

Hierarchical porous zeolitic imidazolate framework‑8 (HpZIF-8) have not only good chemical and thermal stability, but also pore structures of different sizes. In this work, HpZIF-8 supported hollow-fiber liquid-phase microextraction (HpZIF-8@HF-LPME) co-modified with tributyl phosphate and 2-nitroethyl benzene was firstly developed for purification and enrichment of nine typical phenolic pollutants followed by electrophoretic separation and amperometric detection (CE-AD). The key enrichment parameters were optimized by full factorial experimental and central composite designs. Under the optimum conditions, the maximum enrichment factors for the nine analytes were 479 (phenol), 249 (2-chlorophenol), 821 (4-chlorophenol), 1253 (3-methylphenol), 1376 (2,4-dichlorophenol), 1078 (2,4,6-trichlorophenol), 200 (pentachlorophenol), 614 (4-nitrophenol) and1827 times (bisphenol A), respectively. The limits of detection were 0.060-1.5 µg L-1 (S/N = 3) in real sample matrixes. This proposed method has been successfully applied to water samples with high ionic strength, and the average recoveries were in the range of 80.2-118.0%. This developed method of HpZIF-8@HF-LPME/CE-AD needs no desorption and derivatization, providing an alternative for monitoring typical phenolic pollutants in water samples.

Fabricating Materials of Institute Lavoisier-53(Fe)/zeolite imidazolate framework-8 hybrid materials as high-efficiency and reproducible adsorbents for removing organic pollutants

Environmental pollution by emerging contaminants has become an urgent problem. Herein, novel binary metal-organic framework hybrids were constructed from Materials of Institute Lavoisier-53(Fe) (MIL-53(Fe)) and zeolite imidazolate framework-8 (ZIF-8) for the first time. A battery of characterizations were employed to determine the MIL/ZIF hybrids' properties and morphology. Furthermore, the MIL/ZIF towards toxic antibiotics (tetracycline, ciprofloxacin and ofloxacin) were studied to explore their adsorption abilities. The present work disclosed that the obtained MIL-53(Fe)/ZIF-8 = 2:3 possessed an eminent specific surface area with an admirable removal efficiency of tetracycline (97.4%), ciprofloxacin (97.1%) and ofloxacin (92.4%), respectively. The tetracycline adsorption process conformed to the pseudo-second-order kinetic model and this process was more compatible with the Langmuir isotherm model with the highest adsorption capacity of 215.0 mg g^-1. Moreover, the process of removing tetracycline was proved to be spontaneous and exothermic by the thermodynamic results. Furthermore, the MIL-53(Fe)/ZIF-8 = 2:3 towards tetracycline exhibited significant regeneration ability. The effects of pH, dosage, interfering ions and oscillation frequency on tetracycline adsorption capacity and removal efficiency were also investigated. The primary factors contributing to the decent adsorption ability between MIL-53(Fe)/ZIF-8 = 2:3 and tetracycline included electrostatic, π-π stacking, hydrogen bonding and weak coordination interactions. Additionally, we also investigated the adsorption ability in real wastewater. Thus, the proposed binary metal-organic framework hybrid materials can be deemed a promising adsorbent in wastewater purification.

Preparation of Biochar with Developed Mesoporous Structure from Poplar Leaf Activated by KHCO3 and Its Efficient Adsorption of Oxytetracycline Hydrochloride

The effective removal of oxytetracycline hydrochloride (OTC) from the water environment is of great importance. Adsorption as a simple, stable, and cost-effective technology is regarded as an important method for removing OTC. Herein, a low-cost biochar with a developed mesoporous structure was synthesized via pyrolysis of poplar leaf with potassium bicarbonate (KHCO₃) as the activator. KHCO₃ can endow biochar with abundant mesopores, but excessive KHCO₃ cannot continuously promote the formation of mesoporous structures. In comparison with all of the prepared biochars, PKC-4 (biochar with a poplar leaf to KHCO₃ mass ratio of 5:4) shows the highest adsorption performance for OTC as it has the largest surface area and richest mesoporous structure. The pseudo-second-order kinetic model and the Freundlich equilibrium model are more consistent with the experimental data, which implies that the adsorption process is multi-mechanism and multi-layered. In addition, the maximum adsorption capacities of biochar are slightly affected by pH changes, different metal ions, and different water matrices. Moreover, the biochar can be regenerated by pyrolysis, and its adsorption capacity only decreases by approximately 6% after four cycles. The adsorption of biochar for OTC is mainly controlled by pore filling, though electrostatic interactions, hydrogen bonding, and π-π interaction are also involved. This study realizes biomass waste recycling and highlights the potential of poplar leaf-based biochar for the adsorption of antibiotics.

Facile synthesis of dual-hydrolase encapsulated magnetic ZIF-8 composite for efficient removal of multi-pesticides induced pollution in water

Multi-pesticides pollution induced by organophosphorus insecticides (OPs) and aryloxyphenoxypropionate herbicides (AOPPs) has become a significant challenge in bioremediation of water pollution due to their prolonged and over application. Though a number of physical, chemical, and biological approaches have been developed for different pesticides, the explorations usually focus on eliminating single pesticide pollution. Herein, a heterostructure nanocomposite OPH/QpeH@mZIF-8, encapsulating OPs hydrolase OPH and AOPPs hydrolase QpeH in the magnetic zeolitic imidazolate frameworks-8 (mZIF-8), was synthesized through a facile one-pot method in aqueous solution. The immobilized OPH and QpeH in mZIF-8 showed high activities towards the two most common OPs and AOPPs, i.e., chlorpyrifos and quizalofop-P-ethyl, which were hydrolyzed to 3,5,6-Trichloro-2-pyridino (TCP) and quizalofop acid, respectively. Moreover, the magnetic nanocatalyst possessed great tolerance towards broad pH range, high temperatures, and different chemical solvents and excellent recyclability. More importantly, compared to free OPH and QpeH, OPH/QpeH@mZIF-8, with significantly enhanced degradation capability, exhibited enormous potential for simultaneous removal of chlorpyrifos and quizalofop-p-ethyl from the surface and industrial wastewater. Overall, the study demonstrates the applicability of this strategy for utilizing magnetic nanocatalysts encapsulating multiple enzymes due to its simplicity, high efficiency, and economic benefits to removing pesticide compound pollution from various water resources.

Bimetallic MOFs loaded cellulose as an environment friendly bioadsorbent for highly efficient tetracycline removal

Due to the increasingly serious antibiotic-related pollution, it is crucial to develop novel green bioadsorbents to effectively remove antibiotics from aqueous solutions. In this study, Fe doped zeolitic imidazolate frameworks-8 loaded cellulose (Fe/ZIF-8@cellulose) aerogels were prepared. The synthesized Fe/ZIF-8@cellulose aerogels were characterized experimentally including morphology observation and chemical compositions determination. The effects of bioadsorbent dosage, solution pH, adsorption time, initial TC concentration and adsorption temperature on the TC adsorption behaviors were systematically studied. Due to the introduction of Fe in the ZIF-8, the maximum adsorption capacity of Fe/ZIF-8@cellulose for TC could reach as high as 1359.2 mg/g, which is higher than the reported ZIF-8 loaded polysaccharide based adsorbents. The adsorption kinetics and isotherm of TC adsorption were also determined. With the cellulose as the matrix to load Fe/ZIF-8, the obtained Fe/ZIF-8@cellulose aerogels exhibited good reusability. Most importantly, the TC adsorption mechanism was proposed. The results of our finding suggest that the Fe doping into MOFs is an effective strategy to improve the antibiotics adsorption performance and the application of cellulose as the matrix is a valuable method to increase the cyclic utilization. This study highlights the potentials of applying the Fe/ZIF-8@cellulose aerogels in the antibiotics removal for practical wastewater.

Adsorption performance and optimization by response surface methodology on tetracycline using Fe-doped ZIF-8-loaded multi-walled carbon nanotubes

Herein, an iron-doped ZIF-8-loaded multi-walled carbon nanotube (FZM) was synthesized and its adsorption performance on tetracycline (TC) was investigated. The experimental conditions (solution pH, temperature, adsorbent dose) were optimized by Box-Behnken design (BBD) in response surface methodology (RSM). The results show that the adsorption effect of TC by FZM is optimal under the conditions of temperature = 298 K, pH = 6, and contact time = 360 min. The adsorption processes of TC by FZM follow the pseudo-second-order (PSO) kinetic and Freundlich isotherm models, indicating that chemisorption is the dominant factor and the adsorption reaction is multi-layer, with a theoretical maximum saturation capacity of 1111.11 mg/g at 298 K. The adsorption thermodynamic results indicate that the adsorption of TC by FZM is a spontaneous and endothermic process. The mechanism of TC adsorption by FZM possibly occurs through hydrogen bonding, surface complexation, π-π interaction, and electrostatic interaction. From the statistical results, the optimal adsorption capacity of TC by FZM is 599.78 mg/g at a pH of 7.1, a temperature of 312.5 K, and an adsorbent dose of 64.43 mg/L, with a deviation of 1.73% from the actual value. Furthermore, regeneration experiments demonstrate that FZM has excellent reusability with a 15% loss of adsorption capacity after four cycles. This study provides some insights to study the adsorption behavior of TC by MOFs and the optimization of the adsorption experimental conditions, and also shows the potential of FZM for TC removal.

Highly efficient removal of glyphosate from water by hierarchical-pore UiO-66: Selectivity and effects of natural water particles

The selective removal of glyphosate (GP) from aqueous environments is crucial for ensuring human health and environmental sustainability. The preparation of hierarchical-pore MOFs and the reasonable regulation of the pore size are effective strategies for achieving selective removal. In this study, we applied hierarchical-pore UiO-66 analogues (HUiO-66s) synthesized by the template technique through a mild method for the removal of GP from water. The results showed that the maximum adsorption capacity of HUiO-66s was as high as 400 mg/g, which is higher than that of most reported adsorbents. Notably, HUiO-66s showed the highest adsorption rate and distribution coefficient for GP in a multivariate system containing different organophosphorus pesticides and antibiotics, exhibiting suitable selective adsorption performance for GP. Furthermore, GP adsorption onto HUiO-66-2 (prepared from 2 mL of MOF-5 template) did not affect the presence of competing anions and humic acids. Naturally occurring particles in the water body had an enhanced (i.e., Al2O3, sepiolite, and montmorillonite), reduced (i.e., illite and SiO2), or insignificant (i.e., kaolin) effect on the GP adsorption rate of HUiO-66-2. Further analysis based on the bulk adsorption results and microscopic characterisation indicated that the pore structure synergistically occurred with metal-ligand bonding, hydrogen bonding, and electrostatic interactions, which together determined the GP adsorption. Overall, the high adsorption and apparent adsorption selectivity of HUiO-66s facilitated the rapid separation and removal of GP in complex aqueous environments. Our findings provide insights into the transport and fate of MOFs and contaminants in natural aquatic systems.

A simple and green method to prepare non-typical yolk/shell nanoreactor with dual-shells and multiple-cores: Enhanced catalytic activity and stability in Fenton-like reaction

Nowadays, non-typical yolk/shell structure has drawn much attentions due to the better catalytic performance than traditional counterparts (one yolk/one shell). In this study, ZIF-67 @Co₂SiO₄/SiO₂ yolk/shell structure was prepared in one-step at room temperature, in which ZIF-67 was served as the hard-template, H₂O was served as etchant and tetraethyl orthosilicat was served as the raw material for Co₂SiO₄/SiO₂. After calcination, the non-typical Co_xO_y @Co₂SiO₄/SiO₂ yolk/shell nanoreactor with Co₂SiO₄/SiO₂ dual-shells and Co_xO_y multiple-cores was obtained. On the one hand, more active sites were exposed on multiple-cores surface and better protection were provided by dual-shells. On the other hand, the sheet-like Co₂SiO₄ inner shell not only extended the travel path and retention time of pollutants trapped in cavity, but also separated the multiple-cores from aggregation. Therefore, the nanoreactor displayed the outstanding catalytic activity and recyclability in Fenton-like reaction. Metronidazole (20 mg/L) was completely degraded after 30 min, rhodamine B (50 mg/L) and methyl orange (20 mg/L) were removed even within 5.0 min. Catalytic mechanism indicated that ¹O₂ greatly contributed to the pollutant degradation. This paper presented a simple, versatile, green and energy-saving method for non-typical yolk/shell nanoreactor, and it could inspire to prepare other catalysts with high activity and stability for environmental remediation.

Photoassisted highly efficient activation of persulfate over a single-atom Cu catalyst for tetracycline degradation: Process and mechanism

A single-atomic-site Cu catalyst (SAS-Cu) supported on carbon nitride (CN) material was synthesized by a pyrolyzing coordinated polymer (PCP) strategy. The introduction of a single-atomic Cu site improved the charge transfer and separation efficiency. The reaction rate constant of SAS-Cu_1.0 is 4.5 times higher than that of CN. Under the condition of only 0.1 mM sodium persulfate (PS) and 0.1 g/L catalyst, the removal rate of tetracycline (TC) reached 82.5% after 30 min of LED illumination, which greatly improved the utilization of oxidant. Mechanistic analysis shows that there are free radical (•O₂^-, SO₄•^-, •OH) and nonradical pathways (¹O₂ and direct electron transfer) in the system, and they have synergistic effect. Density functional theory (DFT) calculations show that SAS-Cu_1.0 can optimize the adsorption and activation of PS. This work illustrates the application value of SAC combined with activated persulfate and the low energy consumption of the LED light in the field of environment, which provides a new strategy for reducing the salinity and treatment cost of treated water.

Fast cost-effective synthesis of metal ions/biopolymer/silica composites by supramolecular hydrogels crosslink with superior tetracycline sorption performance

In this study, a fast one-pot method was developed for the preparation of Cu/CS/Si ternary composites, which can efficiently remove antibiotic tetracycline from aqueous solutions. Our results demonstrated that the Cu and its content in the composites played a significant role in determining the physical properties and internal morphology of the Cu/CS/Si composites, which subsequently affected the efficiency of the composites for the sorptive removal of tetracycline. Among the studied composites, Cu₃-CS₂-Si materials had the largest sorption capacity for tetracycline (1076.7 mg/g) with a fast sorption kinetics (>99% in 30 min) under a broad working pH range (5-10). The results from the batch sorption experiments, together with spectroscopic and microscopic analyses, collectively indicated that Cu-tetracycline inner-sphere surface complexation through Cu-O bond was responsible for the tetracycline sorption on Cu₃-CS₂-Si. In addition, the Cu₃-CS₂-Si showed an excellent reusability in removing tetracycline. The desired sorption and reuse properties, coupled with the facile and cost-effective synthesis method, indicated that Cu/CS/Si composites have a promising potential for the efficient removal of tetracycline from contaminated solutions.

A ZIF-8-based multifunctional intelligent drug release system for chronic osteomyelitis

Chronic osteomyelitis (COM) is an inflammatory bone disease caused by bacterial infection. Conventional treatment with antibiotics is prone to resistance and other side effects, and it is ineffective against inflammation caused by infection and bone loss. To treat COM comprehensively, based on the acidic microenvironment of osteomyelitis, we used ZIF-8 and celecoxib to construct a multifunctional intelligent drug release system with pH response effect, named CEL@ZIF-8. Material characterization revealed that celecoxib is successfully loaded into ZIF-8. Ion release and drug release experiments indicated that CEL@ZIF-8 can respond well to the pH and intelligently control the release of ions and drugs. Antibacterial assays manifested that CEL@ZIF-8 is able to inhibit the growth of bacteria significantly. In vitro cell experiments demonstrated that CEL@ZIF-8 can significantly up-regulate the expression of osteogenesis-related cytokines and down-regulate the levels of inflammatory factors. Studies verify that the novel drug release system possesses multiple functions: antibacterial, osteogenesis, anti-inflammatory and intelligent release, suggesting a tremendous clinical promise for the treatment of COM.

Recent advances in performance improvement of Metal-organic Frameworks to remove antibiotics: Mechanism and evaluation

Antibiotic pollution is a serious global problem, which may threaten the health of human and ecosystem. Thereinto, water pollution is the most common way. Thus, it is necessary to develop effective methods to remove antibiotics from the natural aqueous environments. Metal-organic Frameworks (MOFs) - based adsorption and photocatalysis strategies have been demonstrated to be efficient, environmental and promising methods to solve antibiotic pollution and repair the environment. In this review, several strategies to improve the properties of MOFs for removal were summarized and discussed. And the removal mechanisms were also discussed. Besides, new and more reliable evaluation methods of MOFs to remove antibiotics were presented, including preferential adsorption (q_p), quantum yields (QY), space time yields (SY) and figure of merit (FOM). This paper provides alternative perspectives for researchers to improve the properties of MOFs and raise analytic efficiency of antibiotic removal.

Spray drying-assisted construction of hierarchically porous ZIF-8 for controlled release of doxorubicin

The intrinsic properties and structure of carrier materials, as well as the drug-loading method, are crucial to the fabrication of high-performance controlled drug release systems. Metal-organic frameworks (MOFs) have attracted great attention in drug delivery due to their rich variety and very precisely designable structures, but their inherent small pores limit their application towards large-size drug molecules. Herein, we report a facile and efficient approach for the construction of hierarchically porous ZIF-8 (HP-ZIF-8) by spray drying. The homogeneously distributed mesopores, which result from the interspaces in the closely arranged nanosized ZIF-8 (N-ZIF-8), can be tuned by adjusting the primary particle size. More importantly, a drug (doxorubicin (DOX), for example) can be simultaneously encapsulated during the fabrication process of HP-ZIF-8, achieving a high loading rate of 79% and an encapsulation efficiency of 79%. Furthermore, we demonstrate that the obtained DOX@HP-ZIF-8 is a pH-responsive system and the release can also be controlled by the mesopore size. Although HP-ZIF-8 shows obvious advantages in drug loading and release performance compared with N-ZIF-8 loaded with DOX by the same solvent adsorption approach, DOX@HP-ZIF-8 displays significantly increased loading capacity (more than 3 times) and the slowest release rate due to its drug-loading method. Their therapeutic efficacy on HeLa cells has also been proved. These findings have important implications for the construction of HP-MOFs as drug carriers and will also present a new platform for controlled drug release and biomedical applications.

Facile fabrication of N-doped hierarchical porous carbons derived from soft-templated ZIF-8 for enhanced adsorptive removal of tetracycline hydrochloride from water

N-doped hierarchical porous carbons (NHPCs) were successfully prepared from soft-templated zeolitic imidazolate framework-8 (ZIF-8) precursors using sodium dodecylbenzene sulfonate (SDBS) as a template through facile one-step carbonization and applied in tetracycline hydrochloride (TCH) adsorption. The NHPC synthesized at 1000 °C with an SDBS/Zn²⁺ molar ratio of 0.075 exhibited the highest TCH adsorption (q_m = 80.92 mg g^-1) owing to its relatively large BET surface area (1067.41 m² g^-1) and pore volume (1.22 cm³ g^-1) and the stronger surface interaction between TCH and NHPCs (HC1000-0.075). Compared with surfactant-free ZIF-8-derived carbon (HC), introduction of SDBS in the ZIF-8 precursor not only improved the pore structure of the carbon materials but also increased the nitrogen content and the number of surface functional groups. Adsorption kinetics and isotherms showed that the pseudo-second-order model and Sips model fit the TCH adsorption behavior on HC and HC1000-0.075 well. Adsorption experiments and characterizations revealed that the adsorption mechanism involved in TCH adsorption on HC1000-0.075 mainly depended on the synergistic effect of pore filling, H-bonding, π-π interactions, and weak electrostatic interactions. This study provides an effective and simple strategy for fabricating MOF-derived NHPCs as a promising adsorbent for the removal of antibiotics from water.

Adsorption of Sulfonamides in Aqueous Solution on Reusable Coconut-Shell Biochar Modified by Alkaline Activation and Magnetization

Biochar is a low-cost adsorbent for sorptive removal of antibiotics from wastewater, but the adsorption efficiency needs to be improved. In this study, coconut-shell biochar was activated with KOH to improve the adsorption efficiency and magnetically modified with FeCl3 to enable recycling. The amount of KOH and the concentration of FeCl3 were optimized to reduce the pollution and production cost. The KOH-activated and FeCl3-magnetized biochar gave good sulfonamide antibiotic (SA) removal. The maximum adsorption capacities for sulfadiazine, sulfamethazine and sulfamethoxazole were 294.12, 400.00 and 454.55 mg g-1, respectively, i.e., five to seven times higher than those achieved with raw biochar. More than 80% of the adsorption capacity was retained after three consecutive adsorption-desorption cycles. A combination of scanning electron microscopy, Brunauer-Emmett-Teller analysis, X-ray diffraction, Fourier-transform infrared and Raman spectroscopies, and magnetic hysteresis analysis showed that KOH activation increased the specific surface area, porosity, and number of oxygen-rich functional groups. Iron oxide particles, which were formed by FeCl3 magnetization, covered the biochar surface. The SAs were adsorbed on the modified biochar via hydrogen bonds between SA molecules and -OH/-COOH groups in the biochar. Investigation of the adsorption kinetics and isotherms showed that the adsorption process follows a pseudo-second-order kinetic model and a monolayer adsorption mechanism. The adsorption capacity at low pH was relatively high because of a combination of π+-π electron-donor-acceptor, charge-assisted hydrogen-bonding, electrostatic, and Lewis acid-base interactions, pore filling, van der Waals forces and hydrophobic interactions. The results of this study show that magnetically modified biochar has potential applications as an effective, recyclable adsorbent for antibiotic removal during wastewater treatment.

A new 3D 8-connected Cd(ii) MOF as a potent photocatalyst for oxytetracycline antibiotic degradation

1 exhibits the best photocatalytic decomposition efficiency towards antibiotic OXY. The plausible photocatalytic mechanism has been explained with the help of the density of states calculations and Hirshfeld surface analysis.

g-C3N4: Properties, Pore Modifications, and Photocatalytic Applications

Graphitic carbon nitride (g-C3N4), as a polymeric semiconductor, is promising for ecological and economical photocatalytic applications because of its suitable electronic structures, together with the low cost, facile preparation, and metal-free feature. By modifying porous g-C3N4, its photoelectric behaviors could be facilitated with transport channels for photogenerated carriers, reactive substances, and abundant active sites for redox reactions, thus further improving photocatalytic performance. There are three types of methods to modify the pore structure of g-C3N4: hard-template method, soft-template method, and template-free method. Among them, the hard-template method may produce uniform and tunable pores, but requires toxic and environmentally hazardous chemicals to remove the template. In comparison, the soft templates could be removed at high temperatures during the preparation process without any additional steps. However, the soft-template method cannot strictly control the size and morphology of the pores, so prepared samples are not as orderly as the hard-template method. The template-free method does not involve any template, and the pore structure can be formed by designing precursors and exfoliation from bulk g-C3N4 (BCN). Without template support, there was no significant improvement in specific surface area (SSA). In this review, we first demonstrate the impact of pore structure on photoelectric performance. We then discuss pore modification methods, emphasizing comparison of their advantages and disadvantages. Each method's changing trend and development direction is also summarized in combination with the commonly used functional modification methods. Furthermore, we introduce the application prospects of porous g-C3N4 in the subsequent studies. Overall, porous g-C3N4 as an excellent photocatalyst has a huge development space in photocatalysis in the future.

Photocatalytic Degradation of Tetracycline in Aqueous Solution Using Copper Sulfide Nanoparticles

In this paper, spherical-shaped pure phase djurleite (Cu31S16) and roxbyite (Cu7S4) nanoparticles were prepared by a solvothermal decomposition of copper(II) dithiocarbamate complex in dodecanthiol (DDT). The reaction temperature was used to control the phases of the samples, which were represented as Cu31S16 (120 °C), Cu31S16 (150 °C), Cu7S4 (220 °C), and Cu7S4 (250 °C) and were characterized by using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and absorption spectroscopy. The samples were used as photocatalysts for the degradation of tetracycline (TC) under visible light irradiation. The results of the study showed that Cu7S4 (250 °C) exhibited the best activity in the reaction system with the TC degradation rate of up to 99% within 120 min of light exposure, while the Cu31S16 (120 °C) system was only 46.5% at the same reaction condition. In general, roxbyite Cu7S4 (250 °C) could be considered as a potential catalyst for the degradation of TC in solution.

Effective removal of levofloxacin drug and Cr(VI) from water by a composed nanobiosorbent of vanadium pentoxide@chitosan@MOFs

Wastewaters is generally polluted with various inorganic and organic contaminants which require effective multipurpose purification technology. In this respect, a novel V₂O₅@Ch/Cu-TMA nanobiosorbent was constructed via encapsulation of nanoscale metal organic frameworks (Cu-TMA) into vanadium pentoxide-imbedded-chitosan matrix to comprehensively investigate its efficiency in removal of levofloxacin drug (LEVO) (e.g., organic pollutant) and chromium (VI) (e.g., inorganic pollutant) from water. Both LEVO drug and Cr(VI) adsorptions were correlated to pseudo-second order (R² = 1) and Langmuir isotherm (R² = 0.9924 for LEVO and R² = 0.9815 for Cr(VI)). Adsorption of Cr(VI) was confirmed to be spontaneous and endothermic reactions, while LEVO was found to proceed via spontaneous and exothermic reactions based on the thermodynamic parameters. The emerged V₂O₅@Ch/Cu-TMA is regarded as an excellent nanobiosorbent for removal of inorganic contaminant as Cr(VI) from all natural water samples (tap, sea and wastewater) with percentages range 92.43%-96.95% and organic contaminant as LEVO drug from tap and wastewater (91.99%-97.20%).

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.

Efficient removal of tetracycline by a hierarchically porous ZIF-8 metal organic framework

Most reported metal organic frameworks (MOFs) have microporous structures and defective active sites, limiting their practical application to macromolecular substances. A hierarchical porous zeolitic imidazolate framework-8 (ZIF-8) was prepared using poly(diallyldimethylammonium chloride) (PDDA) as a structure-directing agent under facile "aqueous room-temperature" conditions to increase the mass transfer and adsorption capacity tetracycline hydrochloride (TCH). The ZIF-8 pore structure and morphology were synchronously tuned by controlling the PDDA molecular weight and dosage. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Bruner-Emmett-Teller (BET), scanning electron microscopy (SEM), NH₃-temperature-programmed desorption (NH₃-TPD) and adsorption results revealed abundant pore structures and open metal sites in the prepared materials, along with excellent TCH adsorption performance compared with ZIF-8, despite decreased BET surface areas. Initial screens revealed large adsorption capacities of hierarchical porous ZIF-8P3(4) (976.8 mg g^-1) due to the presence of more abundant unsaturated metal sites than ZIF-8 and novel hierarchical porous structures. Therefore, TCH adsorption on ZIF-8 and ZIF-8P3(4), including the kinetics, isotherms, thermodynamics and pH effect, was studied. The adsorption process follows pseudo-second-order kinetics and the Freundlich models better, indicating multilayer adsorption of TCH on the surface of the two absorbents. Adsorption behavior test, FTIR, XPS, BET and XRD results show that TCH adsorption on ZIF-8 and ZIF-8P3(4) most likely involves coordination bonds, electrostatic and π-π interactions, hydrogen bonds, and pore-filling effects. This study provides new insights into the template preparation of MOFs with high adsorption performance as potentially economical adsorbents to remove organic matter from contaminated water.

A review of metal organic framework (MOFs)-based materials for antibiotics removal via adsorption and photocatalysis

Antibiotic abuse has led to serious water pollution and severe harm to human health; therefore, there is an urgent need for antibiotic removal from water sources. Adsorption and photodegradation are two ideal water treatment methods because they are cheap, simple to operate, and reusable. Metal organic frameworks (MOFs) are excellent adsorbents and photocatalysts because of their high porosity, adaptability, and good crystal form. The aim of this study is to suggest ways to overcome the limitations of adsorption and photocatalysis treatment methods by reviewing previous applications of MOFs to antibiotic adsorption and photocatalysis. The different factors influencing these processes are also discussed, as well as the various adsorption and photocatalysis mechanisms. This study provides a valuable resource for researchers intending to use MOFs to remove antibiotics from water bodies.

Fast one-step preparation of porous carbon with hierarchical oxygen-enriched structure from waste lignin for chloramphenicol removal

This work explored the use of porous carbon (PC) materials converted from waste lignin as raw materials for the removal of chloramphenicol (CAP) in water. The PC with controllable pores was prepared through a facile, cost-effective one-step method. The physical and chemical properties of the material were characterized by BET, SEM, FT-IR, and XRD, and the best conditions for preparation were selected based on the results of adsorption experiments. The PC, which was prepared at reaction temperature of 800 °C and the K₂CO₃/sodium lignosulfonate mass ratio of 4, namely PC-800-4, had a high specific surface area (1305.5 m² g^-1) and pore volume (0.758 cm³ g^-1). At a lower initial concentration of CAP (C₀ = 120 mg L^-1), the maximum adsorption capacity of this adsorbent was 534.0 mg g^-1 at 303 K. In addition, PC-800-4 maintained good adsorption performance in a wide pH range and strongly resisted the interference of ions and humic acid. The results showed that the adsorption removal CAP was based on physical adsorption and chemical adsorption as a process supplement. The advantages of wide sources, high efficiency and speed, wide application, and rich oxygen-containing functional groups made the adsorbent have great application potential for removal chloramphenicol from water.

Simultaneous introduction of oxygen vacancies and hierarchical pores into titanium-based metal-organic framework for enhanced photocatalytic performance

Photo-generated radicals play an important role in photocatalytic reactions, yet numerous radicals undergo self-quenching before contact with the substrate because of their ultrafast lifetimes and limited diffusion distances, which decreases the utilization of free radicals and reduces the activity of photocatalysts. Herein, both hierarchical pores and oxygen vacancies (OVs) were successfully introduced into a titanium-based metal-organic framework (MOF), namely MIL-125-NH₂ (MIL for Materials of Institut Lavoisier), via a simple and controllable acid etching method. The generation of OVs increased the yield of photogenerated radicals, while the hierarchical pore structure conferred a pore enrichment effect, thus enhancing the utilization of photogenerated radicals. Owing to the synergistic effect of the hierarchical pores and OVs, the obtained single-crystal nanoreactor, H-MIL-125-NH₂-V_O, showed much higher catalytic activity for rhodamine (RhB) degradation than pristine MIL-125-NH₂. In fact, the rate constant for catalytic RhB degradation in H-MIL-125-NH₂-V_O was approximately eight times that of MIL-125-NH₂. This work highlights the significant contribution of both hierarchical pores and OVs to enhancing the photocatalytic performance of MOFs.

Efficient removal of levofloxacin from different water matrices via simultaneous adsorption and photocatalysis using a magnetic Ag3PO4/rGO/CoFe2O4 catalyst

A magnetic Ag₃PO₄/rGO/CoFe₂O₄ ternary catalyst was firstly prepared and used for removing levofloxacin (LVF) from different water matrices via simultaneous adsorption and photocatalysis. Compared with Ag₃PO₄ and Ag₃PO₄/CoFe₂O₄, Ag₃PO₄/rGO/CoFe₂O₄ shows a superior adsorption-photocatalysis performance for LVF elimination since rGO component not only improves the adsorption ability but also enhances the charge separation efficiency of the catalyst. About 90.7% of LVF in distilled water (10 mg/L) was removed by the ternary catalyst after adsorption for 0.5 h and photocatalysis for 1.0 h, and the removal of LVF performed well in the pH range of 3.51-9.47. Singlet oxygen (¹O₂) was the major reactive oxygen species for LVF degradation in Ag₃PO₄/rGO/CoFe₂O₄ system under visible light, as confirmed by the quenching experiments and ESR study. Based on the detected intermediates in the photocatalytic process, the possible LVF degradation pathways were well-established. As-synthesized Ag₃PO₄/rGO/CoFe₂O₄ can also efficiently remove LVF from the different real water matrices (river water, lake water and secondary effluent) via simultaneous adsorption and photocatalysis. Moreover, magnetic Ag₃PO₄/rGO/CoFe₂O₄ can be easily recovered and effectively reused for the removal of LVF in actual water bodies.

Enhanced removal of pefloxacin from aqueous solution by adsorption and Fenton-like oxidation using NH2-MIL-88B

While Fe-based metal-organic frameworks (MOFs) can be used to remove antibiotics by adsorption, knowledge of how antibiotics are degraded by MOFs is still limited. In this study, one Fe-based MOF, NH₂-MIL-88B was used to remove pefloxacin from aqueous solution via a combination of adsorption and Fenton-like oxidation. NH₂-MIL-88B exhibited a high adsorption capacity for pefloxacin (41.37 mg·g^-1), with >99% removal efficiency within 120 min based on Fenton-like oxidation. To better understand the mechanisms involved in integrated adsorption and Fenton-like oxidation, various advanced characterization techniques were used to monitor the changes in morphology and composition of NH_2-MIL-88B before and after removal of pefloxacin. Scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) all supported adsorption and Fenton oxidation of pefloxacin. In addition, the pefloxacin degradation products identified by LC-UV and LC-MS provided information on the potential adsorption-Fenton oxidation mechanism. These results suggested that NH₂-MIL-88B has remarkably potential to be used in an integrated adsorption and Fenton-like process for the removal of antibiotics from aqueous solution.

One-pot synthesis of N-doped carbon intercalated molybdenum disulfide nanohybrid for enhanced adsorption of tetracycline from aqueous solutions

Nitrogen-doped carbon intercalated molybdenum disulfide nanohybrid (NC-MoS₂) with well-interconnected nanosheets was successfully fabricated using a one-pot hydrothermal method and applied as a novel adsorbent to remove tetracycline (TC) from aqueous solutions. Series material characterizations indicated that the intercalation of nitrogen-doped carbon into MoS₂ nanosheets could produce widened interlayer spacing, enlarge the specific surface area and create more extensive functional groups. The adsorption kinetics and isotherms investigations revealed that the pseudo-second-order model and Langmuir isotherm model could fit well the TC adsorption behavior of NC-MoS₂. Particularly, NC-MoS₂ possessed a high maximum adsorption capacity (1128.4 mg/g) that was approximately 2.8 times that of pristine MoS₂ (409.84 mg/g) at 308 K and pH = 6.0 ± 0.1. Furthermore, the relevant thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic. The adsorption process was dependent on multiple interactions including hydrophobicity, π-π stacking interaction and hydrogen bond. These findings demonstrated that NC-MoS₂ had potential applications for treating TC-containing water and broadened the application of metal sulfides in the environmental field.