Preparation of magnetic MIL-101 (Cr) for efficient removal of ciprofloxacin

Synthesis of reusable hierarchical Pore PVDF-MIL-101(Cr) foam for Solid phase extraction of fluoroquinolones from water and its adsorption behavior for anionic and cationic dyes

In this study, a novel hierarchical pore MIL-101(Cr) foam (HPF-MIL-101) was designed and prepared using the sacrificial template method with NaCl as the sacrificial template. This method involved grinding, heating, and washing the NaCl template to produce HPF-MIL-101, with PVDF as the binder and MIL-101(Cr) as the adsorbent. This preparation process is both straightforward and cost-effective, avoiding the use or generation of any organic reagents, thereby offering an environmentally sustainable approach for producing metal-organic framework (MOF) composites. The prepared HPF-MIL-101 exhibited excellent adsorption capabilities for both anionic dye (methyl orange, MO) and cationic dye (methylene blue, MB). The adsorption process followed a pseudo-second-order kinetic model and Friedrich isotherm model, indicating a multilayer adsorption. This is further supported by the Weber-Morris intraparticle diffusion model, which divided the adsorption process into three stages. Furthermore, the adsorption process was consistent with the Freundlich isotherm model, with a correlation coefficient (r) greater than 0.96. HPF-MIL-101 can also be used as an adsorbent for solid phase extraction (SPE). Therefore, an SPE method combined with high-performance liquid chromatography (HPLC) was developed using HPF-MIL-101 as the adsorbent to analyze five fluoroquinolones (FQs) in water samples. This analytical method showed good linearity in the range of 30-2000 ng·mL-1, with excellent linear correlation coefficient (r = 0.9991-0.9999), reasonable extraction recoveries ranging from 80.39 to 112.7 % (RSD ≤ 7.9 %), and low limits of detection (8-30 ng·mL-1). Overall, the results indicated that HPF-MIL-101 not only had a simple, environment-friendly, and pollution-free preparation process but also can be reused for enrichment and detection of trace FQs in water. Thus, HPF-MIL-101 exhibits immense application potential in environmental pollutant removal and also provides a valuable reference for the preparation and application of other MOF composites.

Chitin/calcite composite extracted from shell waste as a low-cost adsorbent for removal of tetracycline and ciprofloxacin: Effects and mechanisms

Recently, water contamination caused by the misuse of antibiotics has become a growing concern. In this study, an economical chitin/calcite composite (CCA) was extracted from crab shell waste, and the effects and mechanisms of its removal of ciprofloxacin (CIP) and tetracycline (TC) from aqueous solution were investigated. The functional groups of chitin and the metal phase of calcite gave CCA the ability to remove antibiotics. Experiments on kinetics, isothermal adsorption, thermodynamics, co-removal, and reusability were conducted to systematically explore the adsorption performances of CCA toward antibiotics. The pseudo-second-order (FSO) and Langmuir models suited the data obtained from experiments best and displayed a good fit for the chemisorption and a certain homogeneity of adsorption sites. At 25 °C, the maximum adsorption capacities (Qmax) toward CIP and TC were 228.86 and 150.76 mg g-1, respectively. The adsorption mechanisms of CCA with TC and CIP are pH dependent since pH can affect the surface charge of CCA and the form in which CIP and TC are existing. The X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) demonstrated that the keto-O and carboxyl groups of CIP and the carbonyl, hydroxyl, and amido groups of TC could be responsible for the binding with the calcite and the functional groups of chitin through surface complexation, cation bridge and hydrogen bonding.

Nanotechnology-assisted treatment of pharmaceuticals contaminated water

The presence of pharmaceutical compounds in wastewater due to an increase in industrialization and urbanization is a serious health concern. The demand for diverse types of pharmaceutical compounds is expected to grow as there is continuous improvement in the global human health standards. Discharge of domestic pharmaceutical personal care products and hospital waste has aggravated the burden on wastewater management. Further, the pharmaceutical water is toxic not only to the aquatic organism but also to terrestrial animals coming in contact directly or indirectly. The pharmaceutical wastes can be removed by adsorption and/or degradation approach. Nanoparticles (NPs), such as 2D layers materials, metal-organic frameworks (MOFs), and carbonaceous nanomaterials are proven to be more efficient for adsorption and/or degradation of pharmaceutical waste. In addition, inclusion of NPs to form various composites leads to improvement in the waste treatment efficacy to a greater extent. Overall, carbonaceous nanocomposites have advantage in the form of being produced from renewable resources and the nanocomposite material is biodegradable either completely or to a great extent. A comprehensive literature survey on the recent advancement of pharmaceutical wastewater is the focus of the present article.

Photo-Fenton degradation of tetracycline antibiotic over MIL-101(Cr)/FeOOH nanocomposite as stable and efficient visible light responsive photocatalyst

Designing an inexpensive, easily synthesized, stable and efficient photocatalyst is a major challenge in photocatalysis area, especially when photo-reaction is performed in aquatic medium to degrade organic pollutants. To this aim, nano-sized MIL-101(Cr) (MIL = Materials Institute Lavoisier), as chemically tolerant metal-organic framework (MOF), was simply prepared via HF-free hydrothermal synthesis procedure. In order to decorate amorphous FeOOH quantum dots (QDs) on the surface of this MOF, various amounts of FeOOH QDs (i.e., 5, 10, 15 and 20 wt%) were synthesized in the presence of MIL-101(Cr) to prepare MIL-101(Cr)/FeOOH(x%) nanocomposites. Decoration of such iron oxide quantum dots on the surface of MIL-101(Cr) and investigation of its activity in photo-Fenton degradation of tetracycline (TC) antibiotic is reported here for the first time. Among the synthesized nanocomposites, MIL-101(Cr)/FeOOH(15%) demonstrated superior photo-Fenton activity in degradation of TC (80%) at short reaction time under optimum reaction condition using the energy-efficient white LED lamps as visible light source. It was observed that the synergy between any component of this photo-Fenton system such as nanocomposite, hydrogen peroxide and visible light is the main reason for enhancement of TC removal over time. Also, neither MIL-101(Cr) nor FeOOH QDs exhibited poor degradation efficiency, which implies the positive role of the coupling of these materials. Furthermore, the stability and recoverability of MIL-101(Cr)/FeOOH(15%) nanocomposite was investigated in four photo-Fenton cycles, which no significant decrease in TC degradation performance was observed.

Magnetic metal-organic frameworks immobilized enzyme-based nano-biocatalytic systems for sustainable biotechnology

Nanobiocatalysts, in which enzyme molecules are integrated into/onto multifunctional materials, such as metal-organic frameworks (MOFs), have been fascinating and appeared as a new interface of nanobiocatalysis with multi-oriented applications. Among various nano-support matrices, functionalized MOFs with magnetic attributes have gained supreme interest as versatile nano-biocatalytic systems for organic bio-transformations. From the design (fabrication) to deployment (application), magnetic MOFs have manifested notable efficacy in manipulating the enzyme microenvironment for robust biocatalysis and thus assure requisite applications in several areas of enzyme engineering at large and nano-biocatalytic transformations, in particular. Magnetic MOFs-linked enzyme-based nano-biocatalytic systems offer chemo-regio- and stereo-selectivities, specificities, and resistivities under fine-tuned enzyme microenvironments. Considering the current sustainable bioprocesses demands and green chemistry needs, we reviewed synthesis chemistry and application prospects of magnetic MOFs-immobilized enzyme-based nano-biocatalytic systems for exploitability in different industrial and biotechnological sectors. More specifically, following a thorough introductory background, the first half of the review discusses various approaches to effectively developed magnetic MOFs. The second half mainly focuses on MOFs-assisted biocatalytic transformation applications, including biodegradation of phenolic compounds, removal of endocrine disrupting compounds, dye decolorization, green biosynthesis of sweeteners, biodiesel production, detection of herbicides and screening of ligands and inhibitors.

Advances in Metal-Organic Frameworks MIL-101(Cr)

MIL-101(Cr) is one of the most well-studied chromium-based metal-organic frameworks, which consists of metal chromium ion and terephthalic acid ligand. It has an ultra-high specific surface area, large pore size, good thermal/chemical/water stability, and contains unsaturated Lewis acid sites in its structure. Due to the physicochemical properties and structural characteristics, MIL-101(Cr) has a wide range of applications in aqueous phase adsorption, gas storage and separation, and catalysis. In this review, the latest synthesis of MIL-101(Cr) and its research progress in adsorption and catalysis are reviewed.

Nanofused Hierarchically Porous MIL-101(Cr) for Enhanced Methyl Orange Removal and Improved Catalytic Activity

Hierarchically porous MIL-101(Cr) (H-MIL-101(Cr)) with meso/macro-pores was directly prepared via nanofusion progress by using butyric acid as a modulating agent. In the methyl orange (MO) adsorption experiments, H-MIL-101(Cr) showed a high adsorption capability of 369.8 mg g⁻¹, which was 1.52-fold greater than that of pristine MIL-101(Cr) (P-MIL-101(Cr)). While in the oxidation reaction of indene and 1-dodecene tests, H-MIL-101(Cr) presented much higher catalytic efficiency, with turnover frequency (TOF) values of 0.7242 mmol g⁻¹ min⁻¹ and 0.1492 mmol g⁻¹ min⁻¹, respectively, which were 28% and 34% greater than that in the case of P-MIL-101(Cr). Thus, compared with P-MIL-101(Cr), H-MIL-101(Cr) exhibited better removal efficiency and higher levels of activity in the oxidation reactions of indene and 1-dodecene. The unique structure of H-MIL-101(Cr) also contributed to its superior performance in these processes.

Preparation of magnetic metal-organic framework MIL-101(Fe) and its application in the extraction of anthraquinones in rhubarb

In this work, a magnetic octahedral metal organic framework (Fe₃ O₄ @NH₂ -MIL-101(Fe)) was synthesized for the magnetic solid phase extraction of three anthraquinones, including aloe-emodin, emodin, and physcion, in rhubarb. The Fe₃ O₄ @NH₂ -MIL-101(Fe) exhibited a high specific surface area of 259.2 m² /g with an average pore size of 6.0 nm and a high magnetic responsivity of 23.4 emu/g, which may be used as an adsorbent for rapid preconcentration and separation of target analytes. The main parameters for magnetic solid phase extraction of anthraquinones, including the amount of adsorbent, extraction time, extraction temperature, extraction pH, elution solvent, and elution time, were systematically optimized. The whole extraction process required a very low amount of adsorbent and a small volume of the sample. Besides, under the optimized conditions, the method showed satisfactory spiked recovery for anthraquinones in the range of 93.3%-109.1%, and the LODs were 1.7-3.4 ng/mL. The RSDs for intra- and inter- day precision were 0.2%-1.3% and 0.2%-0.6%, respectively. The experimental results indicate that the developed method is feasible for the analysis of anthraquinones in rhubarb. This article is protected by copyright. All rights reserved.

Effect of magnetization on the adsorptive removal of an emerging contaminant ciprofloxacin by magnetic acid activated carbon

Magnetic acid activated carbons (MAAC) were prepared from the shells of Sterculia villosa Roxb by activating the biomass and magnetizing it using the co-precipitation technique. Characterization of MAAC prior and post adsorption was performed using various microscopic and spectroscopic analytical techniques, and they verified the formation of magnetic aggregates over porous activated carbon surface. Vibrating Sample Magnetometer (VSM) analysis confirmed the superparamagnetic behaviour of the adsorbent with saturation magnetization (Ms) value of 18.2 emu/g, causing an easy and rapid recovery from the adsorption setup in the presence of an external magnetic field. Langmuir isotherm and pseudo-second-order kinetic model best fit the experimental data with theoretical Langmuir maximum adsorption capacity as 81.97 mg/g and verifying chemisorption type of adsorption process, respectively. Thermodynamic analysis verified the interaction among adsorbate and adsorbent as endothermic, spontaneous, and thermodynamically favourable. Co-existing metal cations showed a significant reduction in ciprofloxacin removal efficiency; co-existing anions, though, showed a negligible influence on the adsorption efficiency of MAAC. Recyclability studies verified that the adsorption efficiency fell from 98% in the first cycle to 43% in the fifth cycle. The Ms value fell to 7.6 emu/g (after five adsorption cycles), affecting the adsorbent's recovery. The Phyto-toxicological assessment was performed to evaluate the environmental risk to human and aquatic life using Vigna mungo seeds. MAAC proved to be an effective and magnetically separable adsorbent for removing antibiotics.

The Effectiveness of MOFs for the Removal of Pharmaceuticals from Aquatic Environments: A Review Focused on Antibiotics Removal

There is an increasing level of various pollutants and their persistence in aquatic environments. The improper use of antibiotics and their inefficient metabolism in organisms result in their release into aquatic environments. Antibiotic abuse has led to hazardous effects on human health. Thereby, efficient removal of pharmaceuticals, particularly antibiotics, from wastewater and contaminated water bodies is greatly interested in international research communities. Metal-organic framework (MOF) materials, as a hybrid group of material containing metallic center and organic linkers, offer a porous structure that is highly efficient for removing different pollutants from contaminated water and wastewater streams. This article aims to review the recent advancement in using MOF-based adsorbents and catalysts for the removal of pharmaceuticals, especially antibiotics, from polluted water. Applying MOFs-based structures for removing antibiotics using photocatalytic removal and adsorptive removal techniques will be discussed and evaluated in this review paper. Various MOF-based materials such as functionalized MOFs, MOF-based composites, magnetic MOF-based composites, MOFs templated-metal oxide catalysts for removing pharmaceuticals, personal care products, and antibiotics from contaminated aqueous media are discussed. Furthermore, effective operational parameters on the adsorption, adsorption mechanisms, adsorption isotherms, and thermodynamic parameters are explained and discussed. Finally, in the concluding remarks, the challenges and future outlooks of using MOFs-based adsorbents and catalysts for removing antibiotics are summarized.

Treatment technologies to mitigate the harmful effects of recalcitrant fluoroquinolone antibiotics on the environ- ment and human health

Antibiotic proliferation in the environment and their persistent nature is an issue of global concern as they induce antibiotic resistance threatening both human health and the ecosystem. Antibiotics have therefore been categorized as emerging pollutants. Fluoroquinolone (FQs) antibiotics are an emerging class of contaminants that are used extensively in human and veterinary medicine. The recalcitrant nature of fluoroquinolones has led to their presence in wastewater, effluents and water bodies. Even at a low concentration, FQs can stimulate antibacterial resistance. The main sources of FQ contamination include waste from pharmaceutical manufacturing industries, hospitals and households that ultimately reaches the wastewater treatment plants (WWTPs). The conventional WWTPs are unable to completely remove FQs due to their chemical stability. Therefore, the development and implementation of more efficient, economical, convenient treatment and removal technologies are needed to adequately address the issue. This review provides an overview of the technologies available for the removal of fluoroquinolone antibiotics from wastewater including adsorptive removal, advanced oxidation processes, removal using non-carbon based nanomaterials, microbial degradation and enzymatic degradation. Each treatment technology is discussed on its merits and limitations and a comparative view is presented on the choice of an advanced treatment process for future studies and implementation. A discussion on the commercialization potential and eco-friendliness of each technology is also included in the review. The importance of metabolite identification and their residual toxicity determination has been emphasized. The last section of the review provides an overview of the policy interventions and regulatory frameworks that aid in retrofitting antibiotics as a central key focus contaminant and thereby defining the discharge limits for antibiotics and establishing safe manufacturing practices.

Enhancement of aqueous stability of NH2-MIL-101(Fe) by hydrophobic grafting post-synthetic modification

The development of water-stable metal-organic frameworks is a critical issue for their photocatalysis applications in water treatment. A phenyl-ethyl side chain with low surface energy was grafted into NH₂-MIL-101(Fe) through a post-synthetic modification (PSM) method. As a result, a novel MIL-101(Fe)-1-(4-(ethyl)phenyl)urea (named MIL-101(Fe)-EPU) was synthesized. Basic morphology, crystal structure, and chemical bond features of MIL-101(Fe)-EPU were retained after PSM. Nitrogen X-ray photoelectron spectroscopy analysis confirmed the successful introduction of the phenyl-ethyl side chain, and this transformation increased its hydrophobicity and water stability. Contact angles of MIL-101(Fe)-EPU to water raised from 59.6 to 140.4°. And its structure maintained intact after 72 h water exposure, indicating higher stability than parent NH₂-MIL-101(Fe). In the photocatalysis reaction with visible light and oxidant donor (H₂O₂), MIL-101(Fe)-EPU demonstrated a degradation efficiency of tetrabromobisphenol A with a reaction rate at 0.0313 min^-1. The predominant reaction mechanism was OH·oxidation. The acid condition was beneficial for this photocatalysis reaction and high stability was observed. Besides, photocatalysis efficiency, crystal structure, and chemical structures were all retained in different actual water mediums, suggesting high adaptability of MIL-101(Fe)-EPU. In general, hydrophobic group grafting using a PSM method endows MIL-101(Fe)-EPU the potentiality as photocatalyst for organic contaminant elimination from water.

The difference in the adsorption mechanisms of magnetic ferrites modified carbon nanotubes

Various ferrites modified carbon nanotubes (MFe₂O₄/CNTs; M = Co, Cu, Mn) were synthesized and characterized using TEM-EDS, FTIR, BET, TG-DTA, VSM, and XRD. MFe₂O₄/CNTs were used as adsorbents for removing ciprofloxacin (CIP), and the adsorption mechanism was revealed in a comparative manner based on the experimental results and density functional theory calculations. The adsorption capacities of CIP on MFe₂O₄/CNTs were 63.32 (Co), 61.60 (Cu), and 46.35 (Mn) mg/g, respectively. Different M components of MFe₂O₄ affected the adsorption behavior of CIP on them, while the specific surface area and total pore volume showed no significant impact. The investigation on the adsorption energy and the bond formation indicated that CIP was more favorably captured by CoFe₂O₄/CuFe₂O₄ than MnFe₂O₄. The local density of states of metal atoms and O atoms (from the ketone or carboxyl groups of CIP) showed that the d-band centers of Co and Cu atoms were above the Fermi level, while that of Mn was below the Fermi level, providing the fundamental understanding of the promoted O adsorption on CoFe₂O₄ and CuFe₂O₄ and restrained adsorption on MnFe₂O₄. This observation was supported by the electron localization function in terms of the stronger charge density overlap between Co-O/Cu-O than that of Mn-O.

Difunctional covalent organic framework hybrid material for synergistic adsorption and selective removal of fluoroquinolone antibiotics

Due to the low efficiency of traditional sewage treatment methods, the effective removal of zwitterionic fluoroquinolone (FQs) antibiotics is of vital significant for environment protection. In this work, a SO₃H-anchored covalent organic framework (TpPa-SO₃H) was deliberately designed by linking phenolic trialdehyde with triamine through Schiff reaction, then low-content Tb³⁺ ions were loaded onto covalent organic framework according to wet-chemistry immersion dispersion method which benefitting for efficient FQs antibiotics uptaking. Tb@TpPa-SO₃H functionalized with regularly distributed sulfonic acid groups and terbium ions which could provide difunctional binding sites. Tb³⁺ sites could capture carboxylic acid group of FQs molecules according to the complexes coordination effect and sulfonic acid sites play a significant role in the adsorption of FQs molecules through electrostatic interaction with amine group. Tb@TpPa-SO₃H with dual complementary function sites exhibited ultra-fast adsorption kinetics (< 2 min, average over 99% removing rate) and high adsorption capacities of 989, 956, and 998 mg g^-1 for Norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), respectively. Furthermore, Tb@TpPa-SO₃H showed excellent selectivity for the adsorption of FQs in tanglesome system. This work not only explored synergistic adsorption in ion-functionalized 2D covalent organic framework with dual binding sites, but also delineated a promising strategy for the elimination of organic pollutants in environmental remediation.

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.

Effects of electrolytes and fractionated dissolved organic matter on selective adsorption of pharmaceuticals on terephthalic acid-based metal-organic frameworks

In this study, we investigated the synergetic effects of coexisting electrolytes and dissolved organic matter (DOM) on Carbamazepine (CBZ) and Ciprofloxacin (CIP) adsorption on the 1D flexible structure of MIL-53(Al) and 3D rigid structure of UiO-66(Zr). The effects of electrolytes on the adsorption of CBZ and CIP on 1D flexible framework of MIL-53(Al) were more significant than those observed from the 3D framework of UiO-66(Zr). The presence of sulfate, nitrate, and phosphate anions indicates high potential to promote the adsorption of CBZ and CIP onto MIL-53(Al) and UiO-66(Zr) because of the decrease of solubility and strengthening of electrostatic interactions by substitution of oxo-anions at the metal complex node via covalent bonding. The lower hydration energy of the potassium ion enhanced CBZ adsorption on MIL-53(Al), while the higher hydration energy of calcium and magnesium ions reduced the adsorption capacity of CBZ and CIP on MIL-53(Al) and UiO-66(Zr). CBZ interacted with fractionated humic acid better than CIP. High-density carboxylic and aromatic functional groups on humic acid ensured that only humic acid larger than 1KDa was adsorbed by MIL-53(Al). Tryptophan-like and humic acid-like DOM were both detected in real hospital effluent, and their effects on CIP and CBZ adsorption onto MIL-53(Al) were investigated. The presence of tryptophan did not affect CBZ adsorption on MIL-53(Al) (except when coexisting with calcium ions). Conversely, tryptophan interfered with CIP adsorption. The presence of humic acid lower than 1KDa promoted the adsorption of CBZ and CIP by increasing the breathing effect of MIL-53(Al)'s 1D flexible framework. The presence of humic acid with molecular size greater than 1KDa enhanced both CBZ and CIP adsorption via a multilayer adsorption mechanism.

Magnetic Metal Organic Framework Immobilized Laccase for Wastewater Decolorization

The laccase enzyme was successfully immobilized over a magnetic amino-functionalized metal–organic framework Fe3O4-NH2@MIL-101(Cr). Different techniques were used for the characterization of the synthesized materials. The Fe3O4-NH2@MIL-101(Cr) laccase showed excellent resistance to high temperatures and low pH levels with a high immobilization capacity and large activity recovery, due to the combination of covalent binding and adsorption advantages. The long-term storage of immobilized laccase for 28 days indicated a retention of 88% of its initial activity, due to the high stability of the immobilized system. Furthermore, a residual activity of 49% was observed at 85 °C. The immobilized laccase was effectively used for the biodegradation of Reactive Black 5 (RB) and Alizarin Red S (AR) dyes in water. The factors affecting the RB and AR degradation using the immobilized laccase (dye concentration, temperature and pH) were investigated to determine the optimum treatment conditions. The optimum conditions for dye removal were a 5 mg/L dye concentration, temperature of 25 °C, and a pH of 4. At the optimum conditions, the biodegradation and sorption-synergistic mechanism of the Fe3O4-NH2@MIL-101(Cr) laccase system caused the total removal of AR and 81% of the RB. Interestingly, the reusability study of this immobilized enzyme up to five cycles indicated the ability to reuse it several times for water treatment.

Series of highly stable Cd(ii)-based MOFs as sensitive and selective sensors for detection of nitrofuran antibiotic

The oxygen atom of the MOF ether-bridging group acts as a Lewis base site, improving the connection and allowing the detection of 10 antibiotics through the fluorescence quenching effect.

Adsorptive removal of pharmaceuticals from water using metal-organic frameworks: A review

Pharmaceutical pollution has emerged as a highly concerned issue due to its adverse effects. Elevated concentrations of pharmaceuticals in water should be regulated to satisfy the requirement for the provision of clean water. Metal-organic frameworks (MOFs) with high specific surface area, controllable porous structure, and facile modification can serve as promising adsorbents for the removal of pharmaceutical contaminants from water. In this review, a selected collection illustrating the reliable strategies and concepts to prepare the MOFs-based materials with superior water stability is described. In addition, recent progress on the adsorptive removal of pharmaceutical pollutant using burgeoning and functional MOFs is also summarized in terms of maximum capacity, equilibrium time, and regenerate ability. Meanwhile, to understand the adsorption mechanism, related interactions including coordination with unsaturated site, pore-filling effect, hydrogen bonding, electrostatic, and π-π stacking are further discussed. Finally, critical perspectives/assessment of future research emphasising on fabricating desirable MOFs and establishing structure-property relationships to facilitate capture performance are identified.

Lewis acid sites in MOFs supports promoting the catalytic activity and selectivity for CO esterification to dimethyl carbonate

We studied the effect of Lewis acidity in metal–organic frameworks (MOFs) on their activity as catalyst supports for the esterification of CO to dimethyl carbonate.

Laccase immobilization on amino-functionalized magnetic metal organic framework for phenolic compound removal

An amino-functionalized magnetic metal organic framework (MOF), Fe₃O₄-NH₂@MIL-101(Cr), was employed for laccase immobilization for the first time. The immobilized laccase was synthesized by the adsorption and covalent binding method, thus exhibited high activity recovery, large immobilization capacity and good tolerance to low pH and high temperature conditions. The excellent stability enabled the immobilized laccase to retain 89% of its initial activity after storage for 28 days. When the ambient temperature reached 85 °C, the immobilized laccase showed 49.1% residual activity even after 6 h preservation. The stability of laccase in organic solvents such as methanol was also greatly improved. Application of the immobilized laccase for 2,4-dichlorophenol removal was also investigated. The adsorption by Fe₃O₄-NH₂@MIL-101(Cr) contributed to a quick removal in the first hour, and the removal efficiency reached 87% eventually. When the reaction was completed, the immobilized laccase could be separated from the solution by a magnet. The results introduced a novel support for laccase immobilization, and the immobilized laccase had great potential in wastewater treatment.

Magnetic nanosorbents with siliceous hybrid shells of alginic acid and carrageenan for removal of ciprofloxacin

Water contamination with antibiotics is a serious environmental threat. Ciprofloxacin (CIP) is one of the most frequently detected antibiotics in water. Herein, silica-based magnetic nanosorbents prepared using three seaweed polysaccharides, alginic acid, κ- and λ-carrageenan, were developed and evaluated in the uptake of ciprofloxacin. The sorbents were firstly characterized in detail to assess their morphology and composition. A systematic investigation was conducted to study the adsorption performance towards CIP, by varying the initial pH, contact time and initial CIP concentration. The maximum adsorption capacity was 464, 423 and 1350 mg/g for particles prepared from alginic acid, κ- and λ-carrageenan respectively. These high values indicate that these materials are among the most effective sorbents reported so far for the removal of CIP from water. The kinetic data were consistent with the pseudo-second-order model. The CIP adsorption on λ-carrageenan particles followed a cooperative process with sigmoidal isotherm that was described by the Dubinin-Radushkevich model. The high charge density of λ-carrageenan and the propensity of CIP molecules to self-aggregate may explain the cooperative nature of CIP adsorption. The sorbents were easily regenerated in mild conditions and could be reused in CIP removal up to 4 times without a significant loss of adsorptive properties.

A hollow mesoporous carbon from metal-organic framework for robust adsorbability of ibuprofen drug in water

Herein, we described a tunable method for synthesis of novel hollow mesoporous carbon (MPC) via direct pyrolysis (800^oC) of MIL-53 (Fe) as a self-sacrificed template. The structural characterization revealed a hollow, amorphous, defective and mesoporous MPC along with high surface area (approx. 200 m² g^-1). For the experiments of ibuprofen adsorption onto MPC, effects of contact time, MPC dosage, ionic strength, concentration and temperature were systematically investigated. The optimal conditions consisted of pH = 3, concentration 10 mg l^-1 and dose of 0.1 g l^-1 for the highest ibuprofen removal efficiency up to 88.3% after 4 h. Moreover, adsorption behaviour, whereby chemisorption and monolayer controlled the uptake of ibuprofen over MPC, were assumed. Adsorption mechanisms including H-bonding, π-π interaction, metal-oxygen, electrostatic attraction were rigorously proposed. In comparison to several studies, the MPC nanocomposite in this work obtained the outstanding maximum adsorption capacity (206.5 mg g^-1) and good reusability (5 cycles); thus, it can be used as a feasible alternative for decontamination of ibuprofen anti-inflammatory drug from water.

Tunable Synthesis of Mesoporous Carbons from Fe₃O(BDC)₃ for Chloramphenicol Antibiotic Remediation

Chloramphenicol (CAP) is commonly employed in veterinary clinics, but illegal and uncontrollable consumption can result in its potential contamination in environmental soil, and aquatic matrix, and thereby, regenerating microbial resistance, and antibiotic-resistant genes. Adsorption by efficient, and recyclable adsorbents such as mesoporous carbons (MPCs) is commonly regarded as a "green and sustainable" approach. Herein, the MPCs were facilely synthesized via the pyrolysis of the metal⁻organic framework Fe₃O(BDC)₃ with calcination temperatures (x °C) between 600 and 900 °C under nitrogen atmosphere. The characterization results pointed out mesoporous carbon matrix (MPC700) coating zero-valent iron particles with high surface area (~225 m²/g). Also, significant investigations including fabrication condition, CAP concentration, effect of pH, dosage, and ionic strength on the absorptive removal of CAP were systematically studied. The optimal conditions consisted of pH = 6, concentration 10 mg/L and dose 0.5 g/L for the highest chloramphenicol removal efficiency at nearly 100% after 4 h. Furthermore, the nonlinear kinetic and isotherm adsorption studies revealed the monolayer adsorption behavior of CAP onto MPC700 and Fe₃O(BDC)₃ materials via chemisorption, while the thermodynamic studies implied that the adsorption of CAP was a spontaneous process. Finally, adsorption mechanism including H-bonding, electrostatic attraction, π⁻π interaction, and metal⁻bridging interaction was proposed to elucidate how chloramphenicol molecules were adsorbed on the surface of materials. With excellent maximum adsorption capacity (96.3 mg/g), high stability, and good recyclability (4 cycles), the MPC700 nanocomposite could be utilized as a promising alternative for decontamination of chloramphenicol antibiotic from wastewater.