Highly Stable Zinc-Based Metal-Organic Frameworks and Corresponding Flexible Composites for Removal and Detection of Antibiotics in Water

Construction of luminescent dye@MOF platforms for sensing antibiotics with enhanced selectivity and sensitivity

The fabrication of luminescent dye@MOF composites has received extensive attentions in the development of realistic sensing applications. Herein, based on two anionic In-MOFs with different pore structure (1 and 2), the charge and size dependent ion-exchange of cationic dyes was investigated, and consequently four luminescent dye@MOF composites (DMASM@1/2 and RhB@1/2) were successfully fabricated and importantly can be regarded as ideal platforms for better understanding of the factors affecting the construction of dye@MOF composites, which may closely related to a well match between the intrinsic properties and size/charge of the fluorescent molecules and the porosity, structure character of the MOF hosts. Furthermore, these four dye@MOF composites were utilized for sensing of different kinds of antibiotics, demonstrating enhanced selectivity and sensitivity. DMASM@1/2 demonstrated excellent selectivity and sensitivity for NFT and NFZ antibiotics, while RhB@1/2 exhibited excellent selectivity and sensitivity for MDZ and DTZ antibiotics. Systematic analysis of the detection mechanism revealed that different energy transfer efficiency and interaction between MOF frameworks and different types of guest dyes led to different selectivity and detection mechanisms for antibiotics. Moreover, high selectivity and sensitivity, low LOD and extraordinary recycling capacity of four dye@MOF composites in the detection of antibiotics promote their excellent prospect in the further practical application.

Ratiometric fluorescent determination of sulfadimethoxine in foods based on a dual-emission metal-organic framework

Ratiometric fluorescence detection is endowed with higher accuracy than single fluorescence signal assay. In this work, we construct a ratiometric fluorescence probe for the facile quantification of sulfadimethoxine (SDM) in foods. By wrapping N-doped carbon dots (N-CDs) and gold nanoclusters (AuNCs) into zeolitic imidazolate framework-8 (ZIF-8), the nanocomposite of N-CDs/AuNCs@ZIF-8 is facilely prepared and emits two fluorescence including 475 nm from N-CDs and 650 nm from AuNCs. Since bovine serum albumin (BSA) is the stabilizer of AuNCs, SDM can form a complex with BSA, resulting in the fluorescence quenching of AuNCs at 650 nm by a static quenching mechanism. In contrast, SDM has a rare influence on the fluorescence of N-CDs (475 nm). As a result, the use of the probe of N-CDs/AuNCs@ZIF-8 for SDM detection enables simultaneous measurement of response signal and reference signal. Under the optimal condition, the SDM assay based on the probe has a good linear relationship within 10 to 2 × 106 ng/mL and the limit of detection (LOD) is low to 1.064 ng/mL. In addition, the fluorescent probe shows good reliability for the detection of SDM in practical food samples.

Simple fluorochromic detection of chromium with ascorbic acid functionalized luminescent Bio-MOF-1

The bioaccumulation of various heavy metals in the environment and agriculture is posing serious hazards to human health. Hexavalent chromium is one of the most encountered heavy metal pollutants. The routine monitoring of Cr(VI) via simple methods assumes great analytical significance in sectors like environmental safety, food quality, etc. This study reports a novel biocompatible and luminescent metal-organic framework (ascorbic acid functionalized Bio-MOF-1) based "Turn-on" nanoprobe for rapid and sensitive optical detection of Cr(VI). Bio-MOF-1 has been synthesized, functionalized with ascorbic acid (AA), and then comprehensively characterized for its key material properties. The presence of Cr(VI) results in the photoluminescence recovery of Bio-MOF-1/AA. Using the above approach, Cr(VI) is detected over a wide concentration range of 0.02 to 20 ng mL-1, with the limit of detection being 0.01 ng mL-1. The nanoprobe is capable of detecting Cr(VI) in real water as well as in some spiked food samples. Hence, the ascorbic acid functionalized Bio-MOF-1 nanoprobe is established as a potential on-field detection tool for Cr(VI).

Recent progresses in synthesis and modification of g-C3N4 for improving visible-light-driven photocatalytic degradation of antibiotics

Graphitic carbon nitride (g-C3N4) is a widely studied visible-light-active photocatalyst for low cost, non-toxicity, and facile synthesis. Nonetheless, its photocatalytic efficiency is below par, due to fast recombination of charge carriers, low surface area, and insufficient visible light absorption. Thus, the research on the modification of g-C3N4 targeting at enhanced photocatalytic performance has attracted extensive interest. A considerable amount of review articles have been published on the modification of g-C3N4 for applications. However, limited effort has been specially contributed to providing an overview and comparison on available modification strategies for improved photocatalytic activity of g-C3N4-based catalysts in antibiotics removal. There has been no attempt on the comparison of photocatalytic performances in antibiotics removal between modified g-C3N4 and other known catalysts. To address these, our study reviewed strategies that have been reported to modify g-C3N4, including metal/non-metal doping, defect tuning, structural engineering, heterostructure formation, etc. as well as compared their performances for antibiotics removal. The heterostructure formation was the most widely studied and promising route to modify g-C3N4 with superior activity. As compared to other known photocatalysts, the heterojunction g-C3N4 showed competitive performances in degradation of selected antibiotics. Related mechanisms were discussed, and finally, we revealed current challenges in practical application.

Zinc(II)-MOF: A Versatile Luminescent Sensor for Selective Molecular Recognition of Flame Retardants and Antibiotics

An exceptional Zinc(II)-organic framework with the formula [{Zn(L4-py)(bdc)}·DMF]n (Zn-MOF) has been constructed solvothermally using a novel linker L4-py {2,7-bis(3-(pyridin-4-ylethynyl)phenyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone}, coligand H2bdc (1,4-benzenedicarboxylic acid), and ZnBF4·xH2O. The ligand L4-py has been fabricated after functionalization of NDA (1,4,5,8-naphthalenetetracarboxylic dianhydride) core with 3-(pyridin-4-ylethynyl)phenyl group. The single-crystal X-ray analysis reveals that Zn-MOF exhibits a comprehensive three-dimensional (3D) framework architecture and features (4)-connected uninodal dia; 4/6/c1; sqc6 topology with point symbol {66} and two-dimensional (2D) + 2D, parallel polycatenation. Notably, Zn-MOF displayed excellent fluorescence phenomenon and stability in water as well as in methanol solvents and was harnessed as a versatile sensor, demonstrating selective and sensitive molecular recognition of flame retardants and antibiotics. Notably, Zn-MOF displayed 57 and 49.5% quenching efficiency for the flame-retardant pentabromophenol (PBP) and 3,3',5,5'-tetrabromobisphenol A (TBPA), respectively. Whereas an outstanding 90% quenching efficiency was observed for antibiotics, tetracycline (TC) and secnidazole (SD). The mechanistic investigations of this luminescence quenching suggest that this might be primarily occurring via the Fourier resonance energy transfer (FRET) and photoinduced electron transfer (PET) mechanisms, which might be assisted by the competitive absorption and host-guest interactions. The π-electron-rich framework structure of sensor Zn-MOF activates this mechanism.

Multiresponsive luminescent sensors for antibiotics and CrVI with two luminescent ZnII/CdII coordination complexes

Two new ZnII/CdII luminescent coordination polymers (CPs) based on the V-shaped bis(imidazole) ligand 3,6-bis (1H-benzo[d]imidazol-1-yl)-9-methyl-9H-carbazole (bbimc) with [1,1'-biphenyl]-4,4'-dicarboxylic acid ligand (H2bpdc) have been synthesized under solvothermal conditions: {[Zn(bbimc)(bpdc)]·DMF·2.5H2O} (CP 1), {[Cd(bbimc)(bpdc)]·2DMF} (CP 2). CP 1 and CP 2 both display a uninodal 4-c unimodal sql topology 2D framework with vertex symbols of {44·62}. In addition, the two identical 2D nets of CP 2 were interpenetrated each other to form a 2D + 2D → 3D and generate a 2-fold interpenetrating architecture. Moreover, sensing investigations of CP 1 and CP 2 revealed that both of compounds can be used as a highly sensitive and selective multi-responsive luminescent sensor for sensing Cr2O72-, CrO42- and antibiotics (TC: Tetracycline; CTC: Chlortetracycline) in H2O by exhibiting fluorescence quenching with significant quenching constants (Ksv = 1.369 × 104 M-1 (Cr2O72-), 2.003 × 104 M-1 (CrO42-), 5.343 × 104 M-1 (TC), 8.706 × 104 M-1 (CTC) for CP 1 and 4.452 × 104 M-1 (Cr2O72-), 2.119 × 104 M-1 (CrO42-), 4.175 × 104 M-1 (TC), 1.257 × 105 M-1 (CTC) for CP 2). The detection limit are 0.67 μM (Cr2O72-), 0.48 μM (Cr2O72-), 0.23 μM (TC), 0.14 μM (CTC) for CP 1 and 0.28 μM (Cr2O72-), 0.54 μM (CrO42-), 0.31 μM (TC), 0.098 μM (CTC) for CP 2, respectively. In addition, the probable fluorescence quenching mechanism was studied through experiment and theoretical calculation and the co-existance of competitive absorption (CA) and photoinduced electron transfer (PET) progress contributed to such sensing processes.

Smartphone-Assisted EY@MOF-5-Based Dual-Emission Fluorescent Sensor for Rapid On-Site Detection of Daclatasvir and Nitenpyram

Fluorescent metal-organic frameworks (MOFs) are promising sensing materials with tunable and robust structural properties and remarkable luminescent capabilities. In this study, a novel dual-emission fluorescent metal-organic framework (EY@MOF-5) composite is synthesized by a one-pot bottle-around-ship approach. Eosin Y (EY) is encapsulated in MOF-5 to enhance its fluorescence properties and selectivity, effectively addressing typical MOF-5 limitations. EY@MOF-5 serves as a versatile dual-functional fluorescent sensor for two different analytes, daclatasvir (DCT) and nitenpyram (NTP), showing an impressive linear range of 10-200 nM and 0.1-300 μM, with detection limits of 233 pM and 65 nM, respectively. The established method is ultrafast, highly sensitive, and extremely selective for DCT and NTP detection in complex biological and food samples. Fluorescence results are compared and validated with the recommended UPLC method. Then, a smartphone-integrated sensing system is introduced for on-site, real-time, and quantitative analysis of DCT and NTP. The smartphone-assisted intelligent sensing method manifests promising results for DCT and NTP monitoring in biological and food samples, demonstrating its promising potential for the on-site detection of biologically and environmentally significant analytes.

Zeolitic imidazolate framework-L loaded on melamine foam for removal tetracycline hydrochloride from water

Zeolitic imidazolate framework-L/melamine foam (ZIF-L/MF) is fabricated by an in situ growth method to treat the tetracycline hydrochloride in wastewater. The results show that a large amount of leaf-like ZIF-L is vertically grown on the MF surface. ZIF-L/MF exhibits well adsorption performance with a maximum adsorption ability of 1346 mg/g. The pseudo-second-order kinetic model and the Langmuir isotherm model are used to describe the adsorption process well. In addition, the influences of pH and coexisting ions are studied. According to the experimental data and analysis, the adsorption mechanisms may involve H-bonding, π-π interaction, and weak electrostatic interaction. A dynamic adsorption experiment is also performed, and the results show that the time required to achieve the same removal efficiency as static adsorption is reduced by half. This work shows that the obtained ZIF-L/MF has practical applications in antibiotic adsorption.

Construction of a novel "self-regenerative" electrochemical biosensor based on metal-organic frameworks and its application to the detection of Mycoplasma ovine pneumonia

This study aimed to prepare a novel "self-regenerative" electrochemical biosensor by successively modifying gold nanoparticles, four-arm polyethylene glycol-NH₂, and NH₂-MIL-53 (Al) (MOF) on the glassy carbon electrode interface. A hairpin G-triplex-mediated DNA (G3 probe) as a part of the mycoplasma ovine pneumonia (MO) gene was loosely adsorbed to MOF. Based on the mechanism of hybridization induction, the G3 probe could effectively detach from the MOF only after introducing the target DNA. Subsequently, its guanine-rich nucleic acid sequences were exposed to solution of methylene blue. As a result, the diffusion current of the sensor system showed a sharp decline. The developed biosensor showed excellent selectivity, and the concentration of target DNA exhibited a good correlation in the range 10^-10 to 10^-6 M with a detection limit of 1.00 pM (S/N = 3), even in 10% goat serum. Most interestingly, this biosensor interface automatically started the regeneration program. Moreover, regeneration could be effectively achieved at least seven times, and the recovery rate of the electrode interface and sensing efficiency was up to 90%. Additionally, this platform could be used for other clinical assays in various systems by simply changing the DNA sequence of the probe.

An ion-coordination hydrogel based sensor array for point-of-care identification and removal of multiple tetracyclines

Misuse and overuse of tetracycline antibiotics (TCs) brings serious issues to ecological environment, food safety and human health. It is urgent to develop unique platform for high efficient identification and removal of TCs. In the present investigation, an effective and simple fluorescence sensor array was constructed based on the interaction between metal ions (Eu³⁺ and Al³⁺) and antibiotics. Benefiting from the different affinities between the ions and TCs, the sensor array can identify TCs from other antibiotics, which also can further differentiating four kinds of TCs (OTC, CTC, TC and DOX) from each other via linear discriminant analysis (LDA) technique. Meanwhile, the sensor array performed well in quantitative analysis of single TC antibiotic and differentiation of TCs mixtures. More interestingly, Eu³⁺ and Al³⁺-doped sodium alginate/polyvinyl alcohol hydrogel beads (SA/Eu/PVA and SA/Al/PVA) were further constructed, which can not only identify the TCs but simultaneously remove the antibiotics with high efficiency. The investigation provided an instructive way for rapid detection and environment protection.

Fabrication of Two Luminescent Imidazolyl Cadmium-Organic Frameworks and Their Sensing Mechanism for 2,6-Dichloro-4-nitroaniline

2,6-Dichloro-4-nitroaniline, alias dicloran (DCN), is a broad-spectrum pesticide that can cause irreversible damage to the human body. Therefore, it is of great significance to develop a technology for the rapid and convenient detection of DCN. Luminescent metal organic frameworks have attracted extensive attention in the field of sensing and detection due to their excellent optical properties. In this study, two kinds of 2D Cd-MOFs (CdMOF-1 and CdMOF-2) were developed for the detection of residual DCN in the environment. Both CdMOFs exhibit excellent solvent and acid-base stability and can respond to DCN quickly and sensitively in a short time (30 s). CdMOFs not only have good selectivity and anti-interference toward DCN but also have good reusability. Under the conditions of DCN concentrations of 1-15 and 0.3-30 μM, the change in fluorescence intensity of CdMOF-1 and CdMOF-2 showed a good linear relationship with DCN concentration (R² = 0.999/0.991), and the detection limits were 0.36 and 0.12 μM, respectively. Through ultraviolet-visible absorption spectroscopy (UV-Vis), X-ray photoelectron spectroscopy, fluorescence lifetime, and density functional theory calculations, it is revealed that the fluorescence quenching mechanisms of DCN for two kinds of Cd-MOFs are competitive absorption and photoinduced electron transfer, and there may be a weak π-π interaction. Finally, it is demonstrated that by using two types of fluorescent CdMOFs to make the fluorescent test paper and detect actual soil, these can be applied to the actual scene and achieve onsite real-time detection.

A Zn(II)-Metal-Organic Framework Based on 4-(4-Carboxy phenoxy) Phthalate Acid as Luminescent Sensor for Detection of Acetone and Tetracycline

As hazardous environmental pollutants, residual tetracycline (TC) and acetone are harmful to the ecosystem. Therefore, it is necessary to detect the presence of these pollutants in the environment. In this work, using Zn (II) salt, 4-(4-carboxy phenoxy) phthalic acid (H₃L), and 3,5-bis(1-imidazolyl) pyridine (BMP), a new metal-organic framework (Zn-MOF) known as [Zn₃(BMP)₂L₂(H₂O)₄]·2H₂O was synthesized using a one-pot hydrothermal method. The Zn-MOF has a three-dimensional framework based on the [Zn1N₂O₂] and [Zn2N₂O₄] nodes linked by a tridentate bridge BMP ligand and an L ligand with the μ₁:η¹η⁰/μ₁:η¹η⁰/μ₀:η⁰η⁰ coordination mode. There were two kinds of left- and right-handed helix chains, Zn1-BMP and Zn1-BMP-Zn1-L. The complex was stable in aqueous solutions with pH values of 4-10. The Zn-MOF exhibited a strong emission band centered at 385 nm owing to the π*→π electron transition of the ligand. It showed high luminescence in some common organic solvents as well as in the aqueous solutions of pH 4-10. Interestingly, TC and acetone effectively quenched the luminescence of the Zn-MOF in aqueous solution and enabled the Zn-MOF to be used as a sensor to detect TC and acetone. The detection limits of TC and acetone were observed to be 3.34 µM and 0.1597%, respectively. Even in acidic (pH = 4) and alkaline (pH = 10) conditions, the Zn-MOF showed a stable luminescence sensing capability to detect TC. Luminescence sensing of the Zn-MOF for TC in urine and aquaculture wastewater systems was not affected by the interfering agent. Furthermore, the mechanism of sensing TC was investigated in this study. Fluorescence resonance energy transfer and photoinduced electron transfer were found to be the possible quenching mechanisms via UV-Vis absorption spectra/the excitation spectra measurements and DFT calculations.

Blood-Coagulation-Inspired Dynamic Bridging Strategy for the Fabrication of Multiscale-Assembled Hierarchical Porous Material

Porous materials, from macroscopic bulk materials (MBs) with (sub-)millimeter-scale pores to tiny particles (TPs) with (sub-)nanometer-scale pores, have attracted ever-growing interest in various fields. However, the integration of multi-scale pores in one composite is promising but challenging, owing to the considerable gap in the scale of the pores. Inspired by blood coagulation, a fibrin-based dynamic bridging strategy is developed to fabricate a multiscale-assembled hierarchical porous material (MHPM), in which fibrin formed as the sub-framework for the weaving-narrow of MBs and the enwinding-load of TPs. The bio-polymerization nature makes the fabrication rapid, facile, and universal for the customizable integration of seven kinds of TPs and four kinds of MBs. Besides, the integration is controllable with high load capacity of TPs and is stable against external shock forces. The unique multi-level structure endows the MHPM with large and accessible surface area, and efficient mass transfer pathways, synergistically leading to high adsorption capacity and rapid kinetics in multiple adsorption models. This work suggests a strategy for the rational multi-level design and fabrication of hierarchical porous architectures.

Highly Luminescent MOF and Its In Situ Fabricated Sustainable Corn Starch Gel Composite as a Fluoro-Switchable Reversible Sensor Triggered by Antibiotics and Oxo-Anions

Frequent use of antibiotics and the growth of industry lead to the pollution of several natural resources which is one of the major consequences for fatality to human health. Exploration of smart sensing materials is highly anticipated for ultrasensitive detection of those hazardous organics. The robust porous hydrogen bonded network encompassing a free-NH₂ moiety, Zn(II)-based metal-organic framework (MOF) (1), is used for the selective detection of antibiotics and toxic oxo-anions at the ppb level. The framework is able to detect the electronically dissimilar antibiotic sulfadiazine and nitrofurazone via fluorescence "turn-on" and "turn-off" processes, respectively. The antibiotic-triggered reversible fluoro-switching phenomena (fluorescence "on-off-on") are also observed by using the fluorimetric method. An extensive theoretical investigation was performed to establish the fluoro-switching response of 1, triggered by a class of antibiotics and also the sensing of oxo-anions. This investigation reveals that the interchange of the HOMO-LUMO energy levels of fluorophore and analytes is responsible for such a fluoro-switchable sensing activity. Sensor 1 showed the versatile detection ability which is reflected by the detection of a carcinogenic nitro-group-containing drug "roxarsone". In view of the sustainable environment along with quick-responsive merit of 1, an in situ MOF gel composite (1@CS; CS = corn starch) is prepared using 1 and CS due to its useful potential features such as biocompatibility, toxicologically innocuous, good flexibility, and low commercial price. The MOF composite exhibited visual detection of the above analytes as well as antibiotic-triggered reversible fluoro-switchable colorimetric "on-off-on" response. Therefore, 1@CS represents a promising smart sensing material for monitoring of the antibiotics and oxo-anions, particularly appropriate for the real-field analysis of carcinogenic drug molecule "roxarsone" in food specimens.

Zinc Oxide/Phosphorus-Doped Carbon Nitride Composite as Potential Scaffold for Electrochemical Detection of Nitrofurantoin

Herein, we present an electrocatalyst constructed by zinc oxide hexagonal prisms/phosphorus-doped carbon nitride wrinkles (ZnO HPs/P-CN) prepared via a facile sonochemical method towards the detection of nitrofurantoin (NF). The ZnO HPs/P-CN-sensing platform showed amplified response and low-peak potential compared with other electrodes. The exceptional electrochemical performance could be credited to ideal architecture, rapid electron/charge transfer, good conductivity, and abundant active sites in the ZnO HPs/P-CN composite. Resulting from these merits, the ZnO HPs/P-CN-modified electrode delivered rapid response (2 s), a low detection limit (2 nM), good linear range (0.01-111 µM), high sensitivity (4.62 µA µM^-1 cm²), better selectivity, decent stability (±97.6%), and reproducibility towards electrochemical detection of NF. We further demonstrated the feasibility of the proposed ZnO HPs/P-CN sensor for detecting NF in samples of water and human urine. All the above features make our proposed ZnO HPs/P-CN sensor a most promising probe for detecting NF in natural samples.

Adsorptive removal of ibuprofen to binary and amine-functionalized UiO-66 in the aquatic environment: synergistic/antagonistic evaluation

The removal of ibuprofen (IBP) from the aqueous solution by metal-organic frameworks such as UiO-66, UiO-66-NH₂, and a binary MOF (UiO-66@5%HKUST-1) was studied. MOFs were synthesized by the solvothermal method. The synthesized MOFs were characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and N₂ adsorption. BET results showed that binary MOF and UiO-66-NH₂ had a smaller surface area and were mesoporous compared to UiO-66, while UiO-66 was microporous. Quantitative investigations were conducted to understand the effect of binary and functional UiO-66 in adsorbing IBP and compared to UiO-66. The results showed that UiO-66 with 213 mg/g had the highest adsorption in comparison to other adsorbents. UiO-66-NH₂ showed the lowest adsorption (96 mg/g) due to a large decrease in the surface area. The binary MOF, despite a slight decrease in surface area (1277.6 m²/g), had lower adsorption than UiO-66 (147 mg/g) due to the antagonistic effects between the adsorbent and IBP. Furthermore, the pH of the solution had a great effect on the adsorption of IBP, and the results showed that increasing the pH values above 4 reduced the adsorption of IBP.

Combined Skeleton and Spatial Rigidification of AIEgens in 2D Covalent Organic Frameworks for Boosted Fluorescence Emission and Sensing of Antibiotics

AIEgens show relatively weak fluorescence performance owing to the existence of π-π interlayer accumulation, molecular layer planarization, and intramolecular rotation in aggregation-induced emission (AIE) molecules, which limit its application scope. Herein, we put forward a combined skeleton and spatial rigidification method to boost the fluorescence emission efficiency of AIEgens. As a proof-of-concept experiment, two highly fluorescent covalent organic frameworks (COFs) were designed and constructed by the Knoevenagel condensation reaction. The experimental results show that the combined skeleton and spatial rigidification endowed excellent fluorescence emission for the resulting F-COF-2 by destruction of the π-π interlayer accumulation, interference of the molecular layer planarization, and restriction of the intramolecular rotation of the AIEgen unit. F-COF-2 displayed highly sensitive and selective NFT and NZF detection. Particularly, the K_sv value and limit of detection of F-COF-2 toward NFT were estimated to be 9.12 × 10⁵ M^-1 and 3.35 ppb, respectively, which surpassed all the reported crystalline porous fluorescent materials. The mechanism study proved that its outstanding fluorescence detection property was ascribed to the formation of a nonfluorescent complex induced by hydrogen bond interactions and electron transfer between F-COF-2 and NFT and NZF. This work not only proposes a combined skeleton and spatial rigidification strategy to improve the fluorescence efficiency of AIE molecules but also develops a sensor with high fluorescence efficiency, high chemical stability, and highly efficient detection of antibiotics.

A cucurbit[6]uril based supramolecular assembly for the detection and removal of dyes and antibiotics from water

A cucurbit[6]uril (CB[6]) based supramolecular assembly CB[6]-[NDS]^2- (1, NDS = 2,6-naphthalenedisulfonic acid anion) was used to detect dyes such as reactive blue 19 (RB19), rhodamine B (RB), methyl orange (MO), methyl red (MR), and methyl violet (MV), and isoquinoline antibiotics such as berberine (BER) and palmatine (PAL) with detection limits of 143, 128, 374, 193, 305, 27 and 34 ppb, respectively. Simultaneously, 1 also displayed high adsorption abilities towards these organic molecules. These results indicate that 1 is a favorable material for the simultaneous selective detection and removal of specific dyes and antibiotics from water, being potentially useful in monitoring water quality and treating wastewater. The possible mechanisms of the detection and adsorption are also proposed.

Two Multiresponsive Luminescent Zn-MOFs for the Detection of Different Chemicals in Simulated Urine and Antibiotics/Cations/Anions in Aqueous Media

Two Zn-MOFs, namely, {[Zn(L)_0.5(bpea)]·0.5H₂O·0.5DMF}_n [LCU-113 (for Liaocheng University)] and {[Zn(L)_0.5(ibpt)]·H₂O·DMF}_n (LCU-114), were synthesized based on flexible tetracarboxylic acid 1,3-bis(3,5-dicarboxyphenoxy)benzene (H₄L) and different N-ligands [bpea = 1,2-dipyridyl ethane; ibpt = 3-(4'-imidazolobenzene)-5-(pyridine-4'-yl)-1,2,4-triazole]. LCU-113 and LCU-114 possess twofold interpenetrating three-dimensional pillared layer structures, in which a two-dimensional layer formed by carboxylic acid and Zn²⁺ ions was pillared by bpea and ibpt, respectively. The two complexes show high water stability and high luminescence sensing performance toward organic solvents, ions, and antibiotics, as well as chemicals, in simulated urine. The investigation showed that (1) LCU-113 and LCU-114 could detect uric acid (UA, 2,6,8-trihydroxypurine, metabolite of purine) and p-aminophenol (PAP, biomarker of phenamine) in simulated urine by luminescence quenching, respectively, and (2) luminescence quenching of LCU-113 and LCU-114 occurred in aqueous solutions of nitrofurazone (NZF), Fe³⁺, and CrO₄^2-/Cr₂O₇^2-. All the above detections have excellent anti-interference ability and recyclability. The luminescence mechanism analysis indicates that weak interactions between the framework structures and the target analytes as well as the energy competition (inner filter effect) play an important role in sensing the above analytes. The practical application for monitoring NZF/Fe³⁺ in water samples was also tested.

Recent Progress in Metal-Organic Framework Based Fluorescent Sensors for Hazardous Materials Detection

Population growth and industrial development have exacerbated environmental pollution of both land and aquatic environments with toxic and harmful materials. Luminescence-based chemical sensors crafted for specific hazardous substances operate on host-guest interactions, leading to the detection of target molecules down to the nanomolar range. Particularly, the luminescence-based sensors constructed on the basis of metal-organic frameworks (MOFs) are of increasing interest, as they can not only compensate for the shortcomings of traditional detection techniques, but also can provide more sensitive detection for analytes. Recent years have seen MOFs-based fluorescent sensors show outstanding advantages in the field of hazardous substance identification and detection. Here, we critically discuss the application of MOFs for the detection of a broad scope of hazardous substances, including hazardous gases, heavy metal ions, radioactive ions, antibiotics, pesticides, nitro-explosives, and some harmful solvents as well as luminous and sensing mechanisms of MOF-based fluorescent sensors. The outlook and several crucial issues of this area are also discussed, with the expectation that it may help arouse widespread attention on exploring fluorescent MOFs (LMOFs) in potential sensing applications.

Flexible metal-organic frameworks for gas storage and separation

Flexible metal-organic frameworks (MOFs) have gradually attracted much attention due to their reversible structural changes and flexible structural responses. The basic research of flexible MOFs is to study their dynamic responses under different external stimuli and translate the responses into applications. Most research studies on flexible MOFs focus on gas storage and separation, but lack a systematic summary. Here, we review the development of flexible MOFs, the structural transformation under the external effects of temperature, pressure, and guest molecules, and their applications in gas storage and separation. Microporous MOFs with flexible structures provide unique opportunities for fine-tuning their performance because the pore shape and size can be controlled by external stimuli. The characteristics of breathing phenomena and large specific surface area make flexible MOFs suitable candidates for gas storage and separation. Finally, the application prospects of flexible MOFs are reported.

Critical review on adsorptive removal of antibiotics: Present situation, challenges and future perspective

This review gives a proper dedicated understanding of the contamination level, sources, and biological dangers related with different classes of antibiotics in consumable water. The literature on the adsorption of antibiotics is relatively uncommon and developments are still under progression, especially for adsorbents other than activated carbon. Also, adsorption technique has already been applied vastly for water treatment. Notwithstanding significant progressions, designed natural wastewater treatment frameworks are just bearably effective (48-77%) in the expulsion of antibiotics. Hence, the compilation of available literature especially for antibiotic adsorption was much needed. Moreover, the conventional adsorbents have some limitations of their own. In this study, the main focus was laid on unconventional adsorbents such as Biochar, Biopolymers, Carbon Nanotubes, Clays, Metal-Organic Frameworks, Microalgae and some miscellaneous adsorbents. The mechanism of adsorption by the unconventional adsorbents includes electrostatic interactions, π-π bonding, weak Van der Waal forces, H-bonding and surface complexation, which was similar to that of conventional adsorbents and hence these unconventional adsorbents can easily replace the costlier conventional adsorbents with even better adsorption efficiency. This paper also briefly discussed the thermodynamics, adsorption equilibrium; isotherm and kinetics of adsorption. This review paper seizes the critical advances of adsorption phenomenon at various interfaces and lays the foundation for current scenario associated with further progress. Besides, this study would help in understanding the antibiotic adsorption, cost estimation and future goals that will attract the young the researchers of this field.

Spinning disc photoreactor based visible-light-driven Ag/Ag2O/TiO2 heterojunction photocatalyst film toward the degradation of amoxicillin

The presence of antibiotics in waste and drinking water is causing increasing concern around the world, thereby an advanced sustainable technology needs to be developed to eliminate the antibiotics from water resources. Hence, an efficient spinning disc photoreactor (SDPR) equipped with visible light-activated Ag/Ag₂O/TiO₂ heterostructure thin film photocatalyst was assessed for the degradation of amoxicillin (AMX) as a typical antibiotic. The surface morphology, optoelectronic and structural features of Ag/Ag₂O/TiO₂ heterojunction were characterized by TEM, BET, mott Schottky, FESEM, EDS, AFM, XRD, UV-Vis-DRS, and contact angle measurements. Results confirm that Ag and Ag₂O have a significant effect on the photocharge carrier separation and transfer of the as-developed photocatalyst system. The operative variables including illumination time, rotational speed, solution flow rate, aeration rate, pH, and initial AMX concentration were optimized by CCD. The results displayed the maximum AMX photodegradation (97.91%) could be achieved at optimal conditions involving illumination time of 80 min, a rotational speed of 225 rpm, the solution flow rate of 0.6 L/min, aeration rate of 20 L/min, pH = 6, and initial AMX concentration of 20 mg/L. Interestingly, more than 79% COD and 64% TOC were removed under optimum conditions during 80 min illumination time, respectively. Active species tests confirmed the dominant role of ·OH and ·O₂^- in AMX degradation. finally, the XRD pattern confirmed that the reusability assessments of the heterojunction film could successfully retain its stability for six consecutive photocatalytic degradation runs. This work demonstrates the feasibility of utilizing visible-light-driven thin-film photocatalysts in spinning disc photoreactors in treating the tenacious antibiotic pollutants.

A novel core-shell coordination assembled hybrid via postsynthetic metal exchange for simultaneous detection and removal of tetracycline

Metal-organic frameworks (MOFs) can perform later transformation without compromising the integrity of the overall framework, and a variety of chemical reactions can be used to modify framework components. Postsynthetic modification (PSM) of MOFs has been developed as an alternative strategy that can expand the range of MOF functional groups. Considering the p-type semiconducting visible light active performance of CuBi₂O₄ (CBO) and the unique porous nanostructure and stability of zeolitic imidazolate framework-8 (ZIF-8), in this work, a novel core-shell coordination assembled hybrid based on p-type semiconductor@MOFs (Eu-CBO@ZIF-8) is prepared for the first time via in-situ growth and postsynthetic metal exchange. A series of detailed characterizations were conducted to confirm the successful synthesis of the material. Moreover, we are focusing on using this material as a new dual-functional sensing material for simultaneous detection and removal of tetracycline (TC), which shows an outstanding analytical performance with a low detection limit of 17 nM, relatively broad linear range (0-70 μM), fast response of less than 120 s, and excellent adsorption performance (377.07 mg g^-1) toward TC. In addition, the sensitive luminescence response caused by TC makes Eu-CBO@ZIF-8 undergo a significant color transition from dark to red under UV-lamps, which is beneficial for visual analysis with the naked eye. The possible detection and adsorption mechanisms, including coordination between Eu³⁺ and the detected substance, the hydrogen bond between ligand and the detected substance, were further discussed. In addition, the practical feasibility of Eu-CBO@ZIF-8 for TC sensing was also studied, with a satisfactory recovery rate of 96.9%-104.6% and RSD ≤3.32%. These results indicate that this material can be used for the detection and adsorption of TC in actual samples.

An yttrium-organic framework based on a hexagonal prism second building unit for luminescent sensing of antibiotics and highly effective CO2 fixation

An yttrium-organic framework based on a hexagonal prism second building unit was constructed from nonanuclear yttrium(iii) and 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine for the luminescent sensing of antibiotics and highly effective CO2 fixation.

Multi-functional metal-organic frameworks for detection and removal of water pollutions

Water pollutions have caused serious threats to the aquatic environment and human health, it is of great significance to monitor and control their contents in water. Compared with the traditional...

Two coordination polymers as multi-responsive luminescent sensors for the detection of UO22+, Cr(vi), and the NFT antibiotic

Two CPs have been synthesized using solvothermal method and can act as multi-responsive luminescent probe to detect UO22+ cation, Cr2O72−/CrO42− anions, and nitrofuran antibiotic in aqueous media with high sensitivity and selectivity.

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.

Metal-Organic Framework Reinforced Acrylic Polymer Marine Coatings

Metal-organic frameworks (MOFs), a class of crystalline, porous, 3D materials synthesized by the linking of metal nodes and organic linkers are rapidly emerging as attractive materials in gas storage, electrodes in batteries, super-capacitors, sensors, water treatment, and medicine etc. However the utility of MOFs in coatings, especially in marine coatings, has not been thoroughly investigated. In this manuscript we report the first study on silver MOF (Ag-MOF) functionalized acrylic polymers for marine coatings. A simple and rapid microwave technique was used to synthesize a two-dimensional platelet structured Ag-MOF. Field tests on the MOF reinforced marine coatings exhibited an antifouling performance, which can be attributed to the inhibition of marine organisms to settle as evidenced by the anti-bacterial activity of Ag-MOFs. Our results indicate that MOF based coatings are highly promising candidates for marine coatings.

Adsorption and convenient ELISA detection of sulfamethazine in milk based on MOFs pretreatment

Metal-organic frameworks (MOFs) has excellent adsorption performance, herein, three kinds of common MOFs were used for the adsorption of sulfamethazine (SM₂) in milk, then enzyme-linked immunosorbent assay (MOF-ELISA) was established. Firstly, NH₂-UiO-66, NH₂-MIL-101, and ZIF-8 were successfully prepared and their adsorption characteristics for SM₂ were investigated. The kinetic models of the three MOFs were more in line with the pseudo-second-order adsorption kinetics, and the saturated adsorption capacity of NH₂-UiO-66, NH₂-MIL-101, and ZIF-8 for SM₂ at 298 K were 139.64, 29.98, and 36.5 mg/g, respectively. Using three different MOFs as adsorbents, the pretreatment of milk samples could be completed within 1 h, the half inhibitory concentrations (IC₅₀) of MOF-ELISA were 1.26, 1.86 and 2.74 ng/mL, the limit of detections (LOD) were 0.05, 0.12, and 0.19 ng/mL and the recovery rate were from 82.30% to 105.62% with the intra-day coefficient of variations (CVs) below 5.81% and inter-day CVs below 7.21%. Detection results showed good correlations with LC-MS/MS (R² > 0.99), indicated that MOFs could effectively eliminate the interference of sample matrix, and has the potential to become a general pretreatment method for the detection of various matrices residues in food safety monitoring.

Dual-emission 3D supramolecular framework hydrogel beads: highly selective detection of antibiotics and mechanism research

Ratiometric fluorescent probes based on coordination polymers (CPs) have been widely applied in optical applications. Therefore, it is very important to develop a dual-emitting gel material based on coordination polymers for specific recognition of molecules. Cu-atda (H2atda = 3,3'-(4-amino-1,2,4-triazol-3,5-diyl) dibenzoic acid) is synthesized with a porous structure and a large number of amino sites exposed on the surface, which can be regarded as a carrier for fluorescent molecules and well disperse in the SA hydrogel network. A dual-emission Eu3+ functionalized CP hydrogel bead (9A/Cu-atda@Eu3+/SA, 9A = 9-anthraldehyde and SA = sodium alginate) is successfully prepared, which presents ratiometric fluorescence detection of flumequine with a low detection limit (48 nM) and high selectivity. Furthermore, it also displays an excellent fluorescence quenching effect on nitrofuran antibiotics, exhibiting a dual functional performance. In addition, the fluorescence response mechanisms of flumequine and nitrofuran antibiotics are discussed in depth. As a portable material, visualization 9A/Cu-atda@Eu3+/SA beads provide an extensive and convenient application prospect for real-time monitoring of antibiotics in the water environment.

Investigation of hierarchically porous zeolitic imidazolate frameworks for highly efficient dye removal

Treatment of textile water containing organic molecules as contaminants still remains a challenge and has become a central issue for environment remediation. Here, a nucleotide incorporated zeolitic imidazolate frameworks (NZIF) featuring hierarchically porous structure served as a potential adsorbent for removal of organic dye molecules. Adsorption isotherms of organic dyes were accurately described by Langmuir adsorption model with correlation coefficients of 0.98 and kinetic data followed the pseudo-second-order model. The maximum adsorption capacity of NZIF for Congo red (CR) and methylene blue (MB) reached 769 and 10 mg/g, respectively, which were 6 and 5 times higher than that of ZIF-8. The adsorption behavior of sunset yellow and crystal violet was examined for mechanism investigation. Analysis of pore size, molecular size, zeta potential and FTIR measurement together revealed that mesopores in NZIF provided more interaction sites and led to enhanced adsorption capacity. Hydrogen bonding and π-π stacking which resulted from the interaction between introduced nucleotide monophosphate and dyes dominated the driving forces for adsorption, where electrostatic interaction was also involved. Moreover, the introduced nucleoside monophosphate enabled NZIF to function under acidic condition whereas ZIF-8 collapsed. This study opens a new avenue for design of porous materials for environment remediation.

Stimuli-Responsive Metal-Organic Framework on a Metal-Organic Framework Heterostructure for Efficient Antibiotic Detection and Anticounterfeiting

Stimuli-responsiveness is an important characteristic that show promising potential in various applications. Herein, a novel ZIF-8-on-Tb-dpn (H₃dpn = 5-(2',4'-dicarboxylphenyl)nicotic acid) heterostructure is constructed using a heteroepitaxial strategy combining the chemical-responsive (antibiotics) and light-responsive behaviors. The pyridine nitrogen of Tb-dpn acts as an anchor site for Zn²⁺, which helps to overcome the limit of lattice mismatch between two metal-organic frameworks (MOFs) and promotes the growth of ZIF-8 nanocrystals. Based on the synergy effect of two MOFs, ZIF-8-on-Tb-dpn exhibits an efficient turn-off response toward tetracycline and chloramphenicol via competitive absorption, Förster resonance energy transfer, and photoinduced electron transfer processes with limit of detection values of 5.6 and 37.6 nM, respectively, which are three- to -fivefold lower than those of Tb-dpn. Moreover, the nanocage of ZIF-8 is utilized to encapsulate photochromic spiropyran (SP) molecules and realize the reversible conversion between SP and merocyanine (MC) under visible light and ultraviolet light. The MC form is accompanied with strong adsorption at 555 nm, which can erase the emission of Tb³⁺. Therefore, a reversible invisible anticounterfeiting pattern is designed with SP ⊂ ZIF-8-on-Tb-dpn for information anticounterfeiting. The excellent stimuli-responsive ability makes the luminescent platform a potential candidate in luminescence applications.

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.