Encapsulation of Luminescent Guests to Construct Luminescent Metal-Organic Frameworks for Chemical Sensing

Optically responsive dry cholesteric liquid crystal marbles

Dry liquid crystal marbles are structures that consist of cholesteric liquid crystal (CLC) droplets prepared by the mixture of chiral-doped thermotropic LCs encapsulated by cellulose nanocrystals (CNCs) that have been dried under ambient conditions. The characterizations revealed that CLC droplets were successfully encapsulated by self-standing CNC shells and responsive to the external gaseous stimulus. The dry LC marbles offer several advantages over previously reported LC-based gas sensors, such as fast response against minor external stimuli, and ease of handling, which make them particularly attractive for practical applications in sensing. We demonstrate the use of these marbles for detecting toluene vapor, a common industrial solvent and pollutant, which we also use to understand the response characteristics. The dry CLC marbles exhibit a significant response to toluene vapor with a detection limit below 500 ppm, attributed to the change of pitch size of the helical structure of CLC droplets induced by the toluene vapor. The CNC-capsulated CLC droplets were stable in emulsion for up to two weeks, and their dried form exhibited a sensitive response upon toluene exposure. The real-time experiments revealed that the LC marbles can be used multiple times without a significant loss of sensitivity, where 90 % of the maximum response was observed at 13.3 ± 4.7 s. These dry LC marbles can also be utilized in other areas, including drug delivery, optical devices, and biosensors.

Linker Engineering toward Tunable Emission Behavior of Porous Interpenetrated Zr-Organic Frameworks

Conjugated molecules with donor-acceptor-donor (D-A-D) moieties have garnered significant attention for their ability to form luminescent metal-organic frameworks (LMOFs). D-A-D molecules feature tunable bandgaps, which can be varied systematically to control the fluorescence wavelength of LMOFs. In this study, we prepared and characterized the fluorescence properties of two porous interpenetrated Zr-organic frameworks (PIZOFs) constructed using 4,4'-(benzo[c][1,2,5]selenadiazole-4,7-diylbis(ethyne-2,1-diyl))dibenzoic acid (L-Se) or 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))dibenzoic acid (L-S) as linkers. The corresponding MOFs are denoted as PIZOF-Se and PIZOF-S, respectively. Through our investigation, we explored the correlation between the structure of the frameworks and their respective optical properties. Our findings revealed that there are distinct differences in the fluorescence properties of the two PIZOFs. Specifically, the fluorescence of PIZOF-S is red-shifted from that characteristic of the corresponding linker, L-S. By contrast, the fluorescence of PIZOF-Se is substantially blue-shifted from that of linker L-Se. The emission of mixed-linker MOFs is explored by combining L-S or L-Se with structurally analogous, but nonfluorescent linker, 4,4'-((perfluoro-1,4-phenylene)bis(ethyne-2,1-diyl))dibenzoic acid (L-F). Based on steady-state and time-resolved photoluminescence experiments, as well as confocal fluorescence microscopy combined with fluorescence lifetime imaging (FILM), we demonstrated that linker engineering is an effective method to tune the emission behavior of LMOFs.

Fluorescent chemosensors facilitate the visualization of plant health and their living environment in sustainable agriculture

Globally, 91% of plant production encounters diverse environmental stresses that adversely affect their growth, leading to severe yield losses of 50-60%. In this case, monitoring the connection between the environment and plant health can balance population demands with environmental protection and resource distribution. Fluorescent chemosensors have shown great progress in monitoring the health and environment of plants due to their high sensitivity and biocompatibility. However, to date, no comprehensive analysis and systematic summary of fluorescent chemosensors used in monitoring the correlation between plant health and their environment have been reported. Thus, herein, we summarize the current fluorescent chemosensors ranging from their design strategies to applications in monitoring plant-environment interaction processes. First, we highlight the types of fluorescent chemosensors with design strategies to resolve the bottlenecks encountered in monitoring the health and living environment of plants. In addition, the applications of fluorescent small-molecule, nano and supramolecular chemosensors in the visualization of the health and living environment of plants are discussed. Finally, the major challenges and perspectives in this field are presented. This work will provide guidance for the design of efficient fluorescent chemosensors to monitor plant health, and then promote sustainable agricultural development.

A fluorescent MOF and its synthesized MOF@cotton composite: Ratiometric sensing of vitamin B2 and antibiotic drug molecule

Here, we demonstrated the synthesis of a zinc based luminescent MOF, 1 (NDC = 2,6- naphthalenedicarboxylate) for the ratiometric detection of biomarker riboflavin (RBF; vitamin B2) in water dispersed medium. Further, this MOF detected two other antibiotic drug molecules, nitrofurantoin (NFT) and nitrofurazone (NZF). The detection of these analytes is very quick (∼seconds), and the limit of detection (LOD) for RBF, NZF and NFT are calculated as 16.58 ppm, 47.63 ppb and 56.96 ppb, respectively. The detection of these analytes was also comprehended by solid, solution, cost-effective paper strip method i.e., triphasic identification capabilities. The sensor is reusable without losing its detection efficacy. The sensor further showed the recognition abilities of these antibiotics in real field samples (river water, urine and tablet) and RBF in vitamin B2 pills and food samples (milk and cold drinks). The sensing merit of 1 urged us to fabricate of 1@cotton fabric composite, which exhibited the colorimetric detection of these analytes. In-depth experimental analysis suggested that the occurrence of photo-induced electron transfer (PET), fluorescence resonance energy transfer (FRET), and the inner filter effect (IFE) are the possible sensing mechanisms for the recognition of the antibiotics drug. The FRET mechanism is responsible for the recognition of RBF. The sensing mechanism is further supported by the theoretical analysis and the excited lifetime measurement.

Ratiometric fluorescence method comprising carbon dots and rhodamine 6G encapsulated in metal-organic framework microcubes for curcumin detection

A ratiometric fluorescence method comprising carbon dots (CDs) and rhodamine 6G (Rh-6G) encapsulated in the microcubes of metal-organic framework (MOF-5) is introduced for the sensitive detection of curcumin (Cur) in condiments. CDs@MOF-5@Rh-6G, synthesized by the adsorption of Rh-6G on MOF-5 embedded with CDs, showed two distinct emission peaks at 435 and 560 nm under excitation at 335 nm, and could be used for Cur detection by ratiometric fluorescence. In the presence of Cur, the fluorescence of the CDs at 435 nm (F435) was quenched by Cur owing to internal filtering and dynamic quenching effects, whereas the emission of Rh-6G at 560 nm (F560) remained unchanged (335 nm is the excitation wavelength, 435 and 560 nm are the emission wavelengths, in which F435/F560 values are used as the output results). Under optimal conditions, a linear relationship was observed between the Cur concentration (in the range 0.1-5 μmol/L) and F435/F560 value for CDs@MOF-5@Rh-6G, with a detection limit of 15 nmol/L. Notably, the proposed method could accurately detect Cur in mustard, curry, and red pepper powders. Therefore, this study could improve the quality control of food and facilitate the development of sensitive ratiometric fluorescence probes.

Anilato-Based Coordination Polymers with Slow Relaxation of the Magnetization: Role of the Synthetic Method and Anilato Ligand

We have prepared and characterized three coordination polymers formulated as [Dy2(C6O4Cl2)3(fma)6] ⋅ 4.5fma (1) and [Dy2(C6O4X2)3(fma)6] ⋅ 4fma ⋅ 2H2O with X=Br (2) and Cl (3), where fma=formamide and C6O4X2 2-=3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion with X=Cl (chloranilato) and Br (bromanilato). Compounds 1 and 3 are solvates obtained with slow and fast precipitation methods, respectively. Compounds 2 and 3 are isostructural and only differ in the X group of the anilato ligand. The three compounds present (6,3)-gon two-dimensional hexagonal honey-comb structures. Magnetic measurements indicate that the three compounds show slow relaxation of the magnetization at low temperatures when a continuous magnetic field is applied, although with different relaxation times and energy barriers depending on X and the crystallisation molecules. Compounds 1-3 represent the first examples of anilato-based lattices with formamide and field-induced slow relaxation of the magnetization.

Lanthanide MOF-based luminescent sensor arrays for the detection of castration-resistant prostate cancer curing drugs and biomarkers

In recent years, castration-resistant prostate cancer (CRPC) has profoundly impacted the lives of many men, and early diagnosis of medication and illness is crucial. Therefore, a highly efficient detection method for CRPC biomarkers and curing drugs is required. However, the complex and diverse structures of CRPC drugs pose significant challenges for their detection and differentiation. Lanthanide metal-organic frameworks (Ln-MOFs) show great potential for sensing applications due to their intense and characteristic luminescence. In this work, a series of new bimetallic Ln-MOFs (EuxTb1-x-MOF) based luminescent sensor arrays have been developed to identify CRPC drugs, including in mixtures, via principal component analysis (PCA) and hierarchical cluster analysis (HCA) methods. These Ln-MOFs are built with a highly conjugated H2L linker (H2L = 5-(4-(triazole-1-yl)phenyl)isophthalic acid) and exhibit robust strong luminescence emissions (mainly located at 543 and 614 nm) and high energy transfer efficiencies. More specifically, Eu0.096Tb0.904-MOF (MOF 3) has demonstrated good sensing performances for CRPC curing drugs in real human serum samples. Furthermore, the curing drug hydroxyflutamide has been combined with MOF 3, to construct a robust composite sensing platform MOF 3@hydroxyflutamide for highly efficient detection of CRPC biomarkers such as the androgen receptor (AR) and prostate-specific antigen (PSA). Finally, luminescence lifetime measurements, zeta potential measurements, and density functional theory (DFT) calculations were performed to gain insights into the sensing mechanism.

A ratiometric fluorescence imprinted sensor based on N-CDs and metal-organic frameworks for visual smart detection of malathion

Sensitive and rapid detection of pesticide residues in food is essential for human safety. A ratiometric imprinted fluorescence sensor N-CDs@Eu-MOF@MIP (BR@MIP) was constructed to sensitively detect malathion (Mal). Europium-based metal organic frameworks (Eu-MOF) were used as supporters to improve the sensitivity of the BR@MIP. N-doped carbon dots (N-CDs) were used as fluorescent source to produce fluorescent signal. A linear relationship between the concentration of Mal and the fluorescence response of the sensor was found in the Mal concentration range of 1-10 μM with a limit of detection (LOD) of 0.05 μM. Furthermore, the sensor was successfully applied for the detection of Mal in lettuce, tap water, and soil samples, with recoveries in the range of 93.0 % - 99.3 %. Additionally, smartphone-based sensors were used to detect Mal in simulated real samples. Thus, the construction of ratiometric imprinted fluorescence sensor has provided a good strategy for the detection of Mal.

Quest for Multifunctionality: Current Progress in the Characterization of Heterometallic Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are a class of porous, crystalline materials that have been systematically developed for a broad range of applications. Incorporation of two or more metals into a single crystalline phase to generate heterometallic MOFs has been shown to lead to synergistic effects, in which the whole is oftentimes greater than the sum of its parts. Because geometric proximity is typically required for metals to function cooperatively, deciphering and controlling metal distributions in heterometallic MOFs is crucial to establish structure-function relationships. However, determination of short- and long-range metal distributions is nontrivial and requires the use of specialized characterization techniques. Advancements in the characterization of metal distributions and interactions at these length scales is key to rapid advancement and rational design of functional heterometallic MOFs. This perspective summarizes the state-of-the-art in the characterization of heterometallic MOFs, with a focus on techniques that allow metal distributions to be better understood. Using complementary analyses, in conjunction with computational methods, is critical as this field moves toward increasingly complex, multifunctional systems.

Coordination polymer gel mediated spectrophotometric, ICP-AES and spectrofluorimetric methods for trace As(III) determination in water and food samples

Herein, a coordination polymer gel is proposed for the determination of As(III) in real samples through multispectroscopic techniques viz. spectrophotometry, spectrofluorimetry, and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Taguchi L32 (46 21) design and adaptive neuro fuzzy inference system (ANFIS) optimized the controllable factors affecting the extraction yielding an experimental S/N ratio of 39.94 dB. The fluorescence quenching (KSV = 2.63 × 106 L mol-1) was static with photoelectron transfer being the main mechanism confirmed by the density functional theory calculations. The limits of detection (LODs), limits of quantification (LOQs) and linear ranges were 0.038 μg L-1, 0.13 μg L-1 and 1.67-116.67 μg L-1, 0.40 μg L-1, 1.21 μg L-1 and 1.67-33.33 μg L-1, 1.07 μg L-1, 3.24 μg L-1 and 3.32-35.37 μg L-1 for the developed enrichment coupled ICP-AES, spectrophotometry and fluorescence sensing methods. Among these methods, the enrichment - ICP-AES method has the lowest LOD, LOQ and the widest linear range followed by the enrichment - spectrophotometry and fluorescene sensing methods. Spectrofluorimetry offers high sensitivity, selectivity, and possible real time monitoring, spectrophotometry provides a cost-effective and versatile option, while ICP-AES manifests multi-element analysis with high sensitivity and low interference. The developed methods were validated and employed for the successful determination of trace As(III) in real samples. The employment of these methods enhances the overall analytical capability for a wide range of sample types and concentrations.

Design and application of dual-emission metal-organic framework-based ratiometric fluorescence sensors

Metal-organic frameworks (MOFs) are novel inorganic-organic hybridized crystals with a wide range of applications. In the last twenty years, fluorescence sensing based on MOFs has attracted much attention. MOFs can exhibit luminescence from metal nodes, ligands or introduced guests, which provides an excellent fluorescence response in sensing. However, single-signal emitting MOFs are susceptible to interference from concentration, environment, and excitation intensity, resulting in poor accuracy. To overcome the shortcomings, dual-emission MOF-based ratiometric fluorescence sensors have been proposed and rapidly developed. In this review, we first introduce the luminescence mechanisms, synthetic methods, and detection mechanisms of dual-emission MOFs, highlight the strategies for constructing ratiometric fluorescence sensors based on dual-emission MOFs, and classify them into three categories: intrinsic dual-emission and single-emission MOFs with luminescent guests, and non-emission MOFs with other luminescent materials. Then, we summarize the recent advances in dual-emission MOF-based ratiometric fluorescence sensors in various analytical industries. Finally, we discuss the current challenges and prospects for the future development of these sensors.

Highly selective detection of 2,4-dinitrophenol by fluorescent NH2-MIL-125(Ti) via dual-parameter sensing technology

The organic contaminant 2,4-dinitrophenol (2,4-DNP) is widely prevalent and poses significant risks to human health. Although numerous in-depth studies having been reported on the highly sensitive detection of 2,4-DNP, there are still challenges to its selective detection. Here, the fluorescence intensity ratio (I0/I) and emission peak shift (Δλ) were utilized for selective detection of 2,4-DNP by NH2-MIL-125(Ti). Notably, the emission peak of the NH2-MIL-125(Ti) suspension exhibited a remarkable red shift in the presence of 2,4-DNP (Δλ = 26 nm), accompanied by the blue shift or weak red shift of analogs, which provided a solid basis for selective detection of 2,4-DNP. Meanwhile, the I0/I ratio of the NH2-MIL-125(Ti) suspension exhibited a robust linear correlation with 2,4-DNP at the low concentration range (0-70 μM). The interaction of the analyte with NH2-MIL-125(Ti) was revealed to involve intermolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET) through XPS, FTIR, and UV-vis absorption spectroscopy. Additionally, we achieved the detection of 2,4-DNP using a smartphone by recognizing both the blue (B) values and the luminance (L) values. The obtained results demonstrated that the NH2-MIL-125(Ti) probe based on dual-parameter sensing technology exhibited excellent potential for selectively detecting 2,4-DNP in water environments, thereby offering significant prospects for its application in water quality assessment.

Pesticides luminescent sensing by a Tb3+-doped Zn metal-organic framework with selectivity towards parathion

Organophosphorus pesticides (OPPs) such as parathion have extensive uses in agriculture and household applications. Chronic exposure to these pesticides can cause severe health and environmental issues. Therefore, a current ecological concern is associated with accumulating these noxious OPPs in food and water sources. In this work, a new Tb3+-doped Zn-LMOF (Zn-LMOF= (3D) {[Zn3(1,4 benzenedicarboxylate)3(EtOH)2]·(EtOH)0.6}∞) was synthesized by a solvent-free reaction between the Zn-LMOF and the salt TbCl3·6H2O using a high-speed ball milling. The Tb@Zn-LMOF was thoroughly characterized by multiple spectroscopic tools, including Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy, and studied in-depth as a luminescent sensor for a series of pesticides (parathion, malathion, methalaxil, carbofuran, iprodione, captan and glyphosate) in aqueous methanol. The Tb@Zn-LMOF is a long-lived green-emitting compound with luminescence originated by an efficient antenna effect from the excited energy levels of Zn-LMOF toward the 5D state of Tb3+ ions, as it is displayed by its strong emission bands at 488, 545, 585, and 620 nm and a lifetime of 1.01 ms upon excitation at 290 nm. Additions of pesticides to a neutral methanolic dispersion of Tb@Zn-LMOF modified its green emission intensity with a pronounced selectivity toward parathion within the micromolar concentration range. The detection limit for parathion was calculated to be 3.04 ± 0.2 μM for Tb@Zn-LMOF. Based on 31P NMR and mass spectrometry studies, it is attributed to the release of lanthanide ions from Tb@Zn-LMOF with the simultaneous formation of a Tb3+-parathion complex.

Cd-MOF and Its Ln3+-Post Modification Products: Regulation of Luminescence Properties and Improved Detection of Uric Acid, Quinine, and Quinidine

One 3D Cd-MOF, namely, {[(HDMA)2][Cd3(L)2]·5H2O·2DMF}n (LCU-124, LCU indicates Liaocheng University), was synthesized from an ether-containing ligand 1,3-bis(3,5-dicarboxylphenoxy)benzene (H4L). Its Ln3+-postmodified samples, Eu3+@LCU-124 and Tb3+@LCU-124, were obtained through cation exchange of dimethylamine cation (HDMA) with Eu3+ and Tb3+. The successful entry of rare earth into LCU-124 by cation exchange modification was verified by IR, XRD, XPS, EDS mapping, and luminescence spectra. The proportion of Eu3+/Tb3+ was adjusted during the modification process, leading to fluorescent materials with different emissions. Luminescence measurements indicated that these complexes exhibited interesting multiresponsive sensing activities toward biomarkers urine acid (UA), quinine (QN), and quinidine (QND). First, LCU-124 has a pronounced quenching effect toward UA with the detection limit of 31.01 μM. After modification, the visualization of the detection was improved significantly and the detection limit of Eu3+@LCU-124 was reduced to 0.868 μM. Second, when QN and QND were present in the suspensions of Eu3+@LCU-124 and Tb3+@LCU-124, strong blue light emission peaks occurred, while the characteristic emission of Eu3+/Tb3+ decreased, forming ratiometric fluorescent sensors with the detection limit in the range of 0.199-9.49 μM. The fluorescent probes have high selectivity, excellent sensitivity recycling, and fast response time (less than 1 min). Besides, a simple logic gate circuit and a range of luminescent mixed matrix membranes were designed to provide simple and fast detection of above biomarkers. Our work indicated that modification of Eu3+/Tb3+ could improve the detection ability significantly.

Tailoring fluorescent ZIF-8 nanostructures through calix[4]pyrrole modification: tunable size and enhanced organic micropollutant removal capacity

Whitish-blue light emitting fluorescent ZIF-8 structures were synthesized by means of bis-carboxylate functional calix[4]pyrrole (BCCP) modification. The calix[4]pyrrole concentration was also manipulated to tune the sizes of the ZIF-8 structures. Moreover, the BCCP-modified ZIF-8 samples exhibited enhanced organic micropollutant removal capacity from aqueous solutions.

The construction of dual-emissive ratiometric fluorescent probes based on fluorescent nanoparticles for the detection of metal ions and small molecules

With the rapid development of fluorescent nanoparticles (FNPs), such as CDs, QDs, and MOFs, the construction of FNP-based probes has played a key role in improving chemical sensors. Ratiometric fluorescent probes exhibit distinct advantages, such as resistance to environmental interference and achieving visualization. Thus, FNP-based dual-emission ratiometric fluorescent probes (DRFPs) have rapidly developed in the field of metal ion and small molecule detection in the past few years. In this review, firstly we introduce the fluorescence sensing mechanisms; then, we focus on the strategies for the fabrication of DRFPs, including hybrid FNPs, single FNPs with intrinsic dual emission and target-induced new emission, and DRFPs based on auxiliary nanoparticles. In the section on hybrid FNPs, methods to assemble two types of FNPs, such as chemical bonding, electrostatic interaction, core satellite or core-shell structures, coordination, and encapsulation, are introduced. In the section on single FNPs with intrinsic dual emission, methods for the design of dual-emission CDs, QDs, and MOFs are discussed. Regarding target-induced new emission, sensitization, coordination, hydrogen bonding, and chemical reaction induced new emissions are discussed. Furthermore, in the section on DRFPs based on auxiliary nanoparticles, auxiliary nanomaterials with the inner filter effect and enzyme mimicking activity are discussed. Finally, the existing challenges and an outlook on the future of DRFP are presented. We sincerely hope that this review will contribute to the quick understanding and exploration of DRFPs by researchers.

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.

Directed assembly of fullerenols via electrostatic and coordination interactions to fabricate diverse and water-soluble metal cation-fullerene nanocluster complexes

Metal ion-nanocluster coordination complexes can produce a variety of functional engineered nanomaterials with promising characteristics to enable widespread applications. Herein, the visualization observation of the interactions of metal ions and fullerene derivatives, particularly anionic fullerenols (Fol), were carried out in aqueous solutions. The alkali metal salts only resulted in salting out of Fol to gain re-soluble sediments, whereas multivalent metal cations (Mn+, n = 2, 3) modulated further assembly of Fol to produce insoluble hybrids. These provide crucial insights into the directed assembly of Fol that two major forces involved in actuation are electrostatic and coordination effects. Through the precise modulation of feed ratios of Fol to Mn+, a variety of water-soluble Mn+@Fol coordination complexes were facilely prepared and subsequently characterized by various measurements. Among them, X-ray photoelectron spectra validated the coordination effects through the metal cation and oxygen binding feature. Transmission electron microscopy delivered valuable information about diverse morphologies and locally-ordered microstructures at the nanoscale. This study opens a new opportunity for developing a preparation strategy to fabricate water-soluble metal cation-fullerenol coordination complexes with various merits for potential application in biomedical fields.

Fluorescence sensing and device fabrication with luminescent metal-organic frameworks

Metal-organic frameworks (MOFs) are a novel class of hybrid porous multi-functional materials consisting of metal ions/clusters and organic ligands. MOFs have exclusive benefits due to their tunable structure and diverse properties. Luminescent MOFs (LMOFs) exhibit both porosity and light emission. They display abundant host and guest responses, making them conducive to sensing. Currently, LMOF sensing research is gaining more depth, with attention given to their device and practical applications. This work reviews recent advancements and device applications of LMOFs as chemical sensors toward ions, volatile organic compounds, biomolecules, and environmental toxins. Furthermore, the detection mechanism and the correlation between material properties and structure are elaborated. This analysis serves as a valuable reference for the preparation and efficient application of targeted LMOFs.

Room-Temperature Synthesized Iron/Cobalt Metal-Organic Framework Nanosheets with Highly Efficient Catalytic Activity toward Luminol Chemiluminescence Reaction

Two-dimensional (2D) iron/cobalt metal-organic framework nanosheets (Fe/Co-MOF NSs) were synthesized via the cooperative self-assembly reaction of Fe3+/Co2+ and terephthalic acid at room temperature. The as-prepared 2D Fe/Co-MOF NSs display superior performance in catalysis of the chemiluminescence (CL) reaction between luminol and H2O2. The CL spectrum, UV-vis absorption spectroscopy, radical scavenger experiments, and electron spin resonance (ESR) spectroscopy are utilized to research the possible CL mechanism of the luminol-H2O2-Fe/Co-MOF NSs system. All results indicate that Fe/Co-MOF NSs present outstanding peroxidase-like activity and could catalyze H2O2 to produce 1O2, O2·-, and ·OH, which could react rapidly with the luminol anion radical and result in strong CL. With the highly efficient CL of the luminol-H2O2-Fe/Co-MOF NSs system, a sensitive sensor for the detection of dopamine (DA) is developed based on the inhibitory effect of DA on the CL intensity. Good linearity over the range of 50-800 nM is achieved with a limit of detection of 20.88 nM (S/N = 3). This research demonstrates that 2D Fe/Co-MOF NSs is a highly effective catalyst for luminol CL reaction and has great application potential in the CL field.

Interfacing metal organic frameworks with polymers or carbon-based materials: from simple to hierarchical porous and nanostructured composites

In the past few years, metal organic frameworks (MOFs) have been assembled with (bio)polymers and a series of carbon-based materials (graphene, graphene oxide, carbon nanotubes, carbon quantum dots, etc.) leading to a wide range of composites differing in their chemical composition, pore structure and functionality. The objective was mainly to overcome the limitations of MOFs in terms of mechanical properties, chemical stability and processability while imparting novel functionality (electron conductivity, (photo)catalytic activity, etc.) and hierarchical porosity. These composites were considered for numerous applications including gas/liquid adsorption and separation, (photo)catalysis, biomedicine, energy storage, conversion and so on. The performance of such composites depends strongly on their microstructural and physico-chemical properties which are mainly driven by the chemical strategies used to design and process such composites. In this perspective article, we propose to cover this topic and provide a useful survey of recent progress in the synthesis and design of MOFs-carbon material composites. This article will describe the development of composites with increasing complexity in terms of porous architecture, spatial structuration and organisation, and functionality.

Formic Acid-Regulated Defect Engineering in Zr-Based Metal-Organic Frameworks toward Fluorescence Sensor for Sensitive Detection of Chlortetracycline

The elaborate defect-engineering of luminescent metal-organic frameworks (MOFs) allows them with enhanced sensing performance. A modulator-induced defect formation strategy is adopted in this paper, and the impact of the open-metal sites on sensing process is rationalized. It is demonstrated that the defect level can be tuned to a remarkable extent by controlling the amount of modulator. When a particular defect concentration is reached, the UiO-66-xFA can be acted as highly sensitive ratiometric fluorescence probes for chlortetracycline (CTE) determination with an ultralow detection limit of 9.9 nm. Furthermore, by virtue of the obvious variation in fluorescence chromaticity of probes from blue to yellow, a sensory hydrogels-based smartphone platform is proposed for visible quantitation of CTE by identifying the RGB values. A delicate device integrated with UV lamp and dark cavity has been developed for avoiding inconsistencies of ambient light and visual errors. Finally, the sensor obtains satisfactory results in the detection of actual seafood samples, with no significant differences from those of liquid chromatography-mass spectrometry. This approach anticipates a novel route to sensitize optical sensors through the design and synthesis of moderate defects in luminescent MOFs.

Construction and Application of Multipurpose metal-organic frameworks -based Hydrogen Sulfide Probe

Hydrogen sulfide (H2S) is a toxic gas derived from the sulfur industry and trace H2S in the environment can cause serious ecological damage while inhalation can cause serious damage and lead to disease. Therefore, the real-time and accurate detection of trace sulfur ions is of great significance for environmental protection and early disease detection. Considering the shortcoming of current H2S probes in terms of stability and sensitivity, the development of novel probes is necessary. Herein, a novel metal-organic frameworks (MOF)-based material, UiO-66-NH2@BDC, was designed and prepared for the visual detection of H2S with rapid response (< 6 s) and low detection limit of S2- (0.13 µM) by hydrogen bonding. Based on its good optical performance, the UiO-66-NH2@BDC probe can detect S2- in various water environments. More importantly, UiO-66-NH2@BDC probe realize imaging S2- in cells and live zebrafish.

Advantages of Slow Sensing for Ambient Monitoring: A Practical Perspective

Air pollution is a ubiquitous threat, affecting 99% of the global populace and causing millions of premature deaths annually. Monitoring ambient air quality is essential, aiding policymakers and environmental agencies in timely interventions. This study delves into the advantages of slower gas sensors over their ultrafast counterparts, with a keen focus on their practicality in real-world scenarios. Slow sensors offer accurate time-averaged exposure assessments, harmonizing with established regulatory benchmarks. Their heightened precision and reliability, complemented by their cost-effectiveness, render them eminently suitable for large-scale deployment. The slow sensing ensures compatibility with regulations, fostering robust risk management practices. In contrast, ultrafast sensors, while claiming rapid detection, despite touting swift detection capabilities, grapple with formidable challenges. The sensitivity of ultrafast sensors to uncontrolled atmospheric effects, fluctuations in pressure, rapid response times, and uniform gas dispersion poses significant hurdles to their reliability. Addressing these issues assumes paramount significance in upholding the integrity of air quality assessments.

Phenylalanine-Based Co2+ and Cd2+ 1D Coordination Polymers: Structural Properties and Catalytic Application for Solvent-Free Aerobic Oxidation of Cycloalkene

Two 1D coordination polymers (CPs) with general formula [M(L)(H2O)(AcO)]n, (M = Co (1) or Cd (2), AcO = acetate anion and L denotes l-phenylalanine based ligand), were synthesized and fully characterized by various spectroscopies (UV-vis, FTIR, and NMR), thermal techniques, magnetic measurements (for 1), and single-crystal and powder X-ray diffraction studies. They can be described as "ribbon-like" 1D polymers constructed through a zigzag arrangement. The polymeric structure is developed due to the coordination mode adopted by the amino acid ligand, classified as μ3-N1O1:O1:O2, which simultaneously links three metal centers. This moiety also plays an important role as a magnetic coupler between metal centers in the cobalt system, which shows a weak antiferromagnetic interaction. Both CPs have also been used in the catalytic oxidation of cyclohexene with molecular oxygen (O2) as an oxidant. Under mild conditions, both compounds demonstrated remarkable catalytic activity, with the cobalt system being more efficient than the cadmium analogue (conversion: 73 and 58% and selectivity for the major product, 2-cyclohexanone: 63 and 55%, for 1 and 2, respectively). Leaching experiments and the results obtained using a radical quencher are consistent with a radical-mediated mechanism for the Co compound. The presence of the superoxide radical was also confirmed using EPR spectroscopy and DMPO as a spin trap, which was further validated by DFT calculations. The activity observed for the Cd analogue is attributed to the organic scaffold assisted by the templating effect of the metal ion.

A highly sensitive fluorescence "on-off-on" sensing platform for captopril detection based on AuNCs@ZIF-8 nanocomposite

Here, a novel fluorescent sensing strategy is established for the detection of captopril (CP) sensitively on the basis of a nanocomposite of gold nanoclusters (AuNCs) and metal-organic framework (AuNCs@ZIF-8). The aggregation-induced emission (AIE) effect will be triggered when AuNCs is encapsulated by metal-organic framework (MOF) which served as a carrier since it limits the molecular motion of AuNCs, and the fluorescence of AuNCs greatly enhanced about 5-time after forming the nanocomposites of AuNCs@ZIF-8. The strong orange-emission at 562 nm was quenched in the presence of mercury ions through dynamic quenching. After adding captopril, the quenched fluorescence of AuNCs@ZIF-8/Hg2+ system would be restored due to the specific interaction among captopril with mercury ions. Simultaneously, the restored degree of AuNCs@ZIF-8/Hg2+ fluorescence depended on the concentration of captopril. Hence, with AuNCs@ZIF-8 serving as reporter signal, the captopril content can be monitored by an "on-off-on" fluorescence sensing mode with a linear relationship of 1-100 μM, and the limit of detection for captopril was 0.134 μM.

Recent Advances in Multifunctional Reticular Framework Nanoparticles: A Paradigm Shift in Materials Science Road to a Structured Future

Porous organic frameworks (POFs) have become a highly sought-after research domain that offers a promising avenue for developing cutting-edge nanostructured materials, both in their pristine state and when subjected to various chemical and structural modifications. Metal-organic frameworks, covalent organic frameworks, and hydrogen-bonded organic frameworks are examples of these emerging materials that have gained significant attention due to their unique properties, such as high crystallinity, intrinsic porosity, unique structural regularity, diverse functionality, design flexibility, and outstanding stability. This review provides an overview of the state-of-the-art research on base-stable POFs, emphasizing the distinct pros and cons of reticular framework nanoparticles compared to other types of nanocluster materials. Thereafter, the review highlights the unique opportunity to produce multifunctional tailoring nanoparticles to meet specific application requirements. It is recommended that this potential for creating customized nanoparticles should be the driving force behind future synthesis efforts to tap the full potential of this multifaceted material category.

Chemorobust dye-encapsulated framework as dual-emission self-calibrating ratiometric sensor for intelligent detection of toluene exposure biomarker in urine

By taking advantages of confinement effect can effectively prevent dye aggregation caused luminescent quenching, Eosin Y (EY) was encapsulated into a chemorobust porous CoMOF as secondary fluorescent signal to construct the dual-emitting sensor of EY@CoMOF. And the photo-induced electron transfer from CoMOF to EY molecules induced EY@CoMOF presenting a weak blue emission at 421 nm and a strong yellow emission at 565 nm. Those dual-emission features also endow EY@CoMOF itself great potentials as a self-calibrating ratiometric sensor in visually and efficiently monitoring hippuric acid (HA) in urine, with fast response, high sensitivity and selectivity, excellent recyclable, and low LOD (0.24 μg/mL). Furthermore, based on a tandem combinational logic gate, an intelligent detection system was designed to improve the practicability and convenience of HA detection in urine. To the best of our knowledge, this is the first example of dye@MOF based sensor for HA detection. And this work provides a promising approach for developing dye@MOF based sensors to intelligent detect bioactive molecules.

A UOF based on a cyclotriphosphazene skeleton: fluorescence sensing of different substituted aldehydes and NACs

A novel uranyl organic framework (U-hdpcp) based on flexible cyclic triphosphazene polycarboxylate ligands was prepared, which possesses the ability to sense aromatic aldehyde solutions (benzaldehyde, salicylaldehyde and 2-bromobenzaldehyde) and nitro compounds (2,4,6-trinitrophenol, 2,4-dinitrophenol and o-nitrophenol). A fluorescent thin film based on U-hdpcp@PVA with the ability to sense aldehyde vapors was prepared via a spin coating method. The work expands the library of UOF materials based on large-sized carboxylic acid ligands and demonstrates promising applications in the field of fluorescent sensors.

A Zn(II) coordination polymer as a dual sensor for ppb level detection of antibiotics and organo-toxins in a green solvent

Herein, we describe the synthesis of a new fluorescent d¹⁰ coordination polymer, [Zn₂(CFDA)₂(BPEP)]_n·nDMF (CP-1) under solvothermal reaction condition using zinc metal ion. In CP-1, Zn(II) ion along with CFDA and BPED ligand forms a 2-fold self-interpenetrated 3D coordination polymers. This CP-1 is characterized by the single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), infrared spectra, optical microscope image and thermogravimetric analysis and the framework is found to maintain its structural stability in different solvents. The framework (CP-1) detected antibiotics (NFT (nitrofurantoin) and NZF (nitrofurazone)) and organo-toxin trinitrophenol in aqueous dispersed medium. Apart from the fast responsive (10 s), the detection limit for them was found at ppb level. The detection of these organo-aromatics were also comprehended by the colorimetric response through solid, solution and low cost paper strip technique i.e., triple mode recognition capability. The probe is re-usable without changing in its sensing efficiency and in addition, it has been applied for the detection of these analytes in the real field specimens (soil, river water, human urine and commercial tablet). The sensing ability is established by in-depth experimental analysis and the life time measurement where mechanism such as photo induced electron transfer (PET), fluorescence resonance energy transfer (FRET), inner filter effect (IFE) was recognized. The presence of guest interaction sites on the linker backbone in CP-1 induces diverse supramolecular interaction with the targeted analytes results to bring them in proximity for the occurrence of these sensing mechanism. The Stern-Volmer quenching constant values of CP-1 for the targeted analytes are admirable and the low detection limit (LOD) values for NFT, NZF and TNP are found to be 34.54, 67.79 and 43.93 ppb respectively. Further, the DFT theory is carried out in details to justify the sensing mechanism.

Construction of High Quantum Yield Lanthanide Luminescent MOF Platform by In Situ Doping and Its Temperature Sensing Performance

Lanthanide luminescent MOF materials show excellent luminescent properties. However, obtaining lanthanide luminescent MOFs with high quantum yield is a challenging research. A novel bismuth-based metal-organic framework [Bi(SIP)(DMF)₂] was constructed by solvothermal method, utilizing 5-sulfoisophthalic acid monosodium salt (NaH₂SIP) and Bi(NO₃)₃·5H₂O. Thereafter, doped MOFs (Ln-Bi-SIP, Ln = Eu, Tb, Sm, Dy, Yb, Nd, Er) with different luminescent properties have been obtained by in situ doping with different lanthanide metal ions, among which Eu-Bi-SIP, Tb-Bi-SIP, Sm-Bi-SIP, and Dy-Bi-SIP have high quantum yield. What is special is that the doping amount of Ln³⁺ ions is very low, and the doped MOF can achieve high luminescence quantum yields. EuTb-Bi-SIP obtained by Eu³⁺/Tb³⁺ codoping and Dy-Bi-SIP exhibit good temperature sensing performance over a wide temperature range with the maximum sensitivity S_r of 1.6%·K^-1 (433 K) and 2.6%·K^-1, respectively (133 K), while the cycling experiments also show good repeatability in the assay temperature range. Finally, considering the practical application value, EuTb-Bi-SIP was blended with an organic polymer poly(methyl methacrylate) (PMMA) to produce a thin film, which shows different color changes at different temperatures.

Two anthracene-based zirconium metal-organic frameworks with fcu and hcp topologies as versatile fluorescent sensors for detection of inorganic ions and nitroaromatics

Two anthracene-based zirconium metal-organic frameworks (UiO-68-AN-fcu and UiO-68-AN-hcp) with blue emission were synthesized by the solvothermal reaction of ZrCl₄ with anthracene-based ligand 4,4'-(9,10-anthracenediyl)dibenzoic acid. The two MOFs inherited the luminescence properties of anthracene-based ligand and exhibited different topologies due to the change of connection mode of Zr-O clusters. The two stable anthracene-based zirconium MOFs served as luminescent sensors for selectively detecting 2-nitrophenol, Fe³⁺ and Cr₂O₇^2-. UiO-68-AN-hcp with flower morphology exhibited stronger quenching effect for 2-nitrophenol, Fe³⁺ and Cr₂O₇^2- by comparing to UiO-68-AN-fcu. Adsorption tests, fluorescence lifetime and spectroscopy studies demonstrated that the fluorescence responses of MOFs for analytes can be primarily attributed to the dynamic quenching mechanism involving energy and electron transfer. These results revealed that the combination of luminescent anthracene-based ligand and Zr-O clusters is a feasible strategy to construst MOFs-based fluorescent sensors.

Rapid detection of the biomarker for cystinuria by a metal-organic framework fluorescent sensor

Arginine (Arg) is considered a valuable biomarker for various diseases, including cystinuria, and its concentration level holds significant implications for human health. To achieve the purposes of food evaluation and clinical diagnosis, it is imperative to develop a rapid and facile method for selective and sensitive determination of Arg. In this work, a novel fluorescent material (Ag/Eu/CDs@UiO-66) was synthesized by encapsulating carbon dots (CDs), Eu³⁺ and Ag ⁺ into UiO-66. This material can serve as a ratiometric fluorescent probe for detecting Arg. It exhibits a high sensitivity with a detection limit of 0.74 μM and a relatively broad linear range from 0-300 μM. After dispersing the composite Ag/Eu/CDs@UiO-66 in an Arg solution, the red emission of Eu³⁺ center at 613 nm was significantly enhanced, while the characteristic peak of CDs center at 440 nm remained unchanged. Therefore, a ratio fluorescence probe could be constructed based on the peak height ratio of the two emission peaks to achieve selective detection of Arg. In addition, the remarkable ratiometric luminescence response induced by Arg results in a significant color transition from blue to red under UV-lamp for Ag/Eu/CDs@UiO-66, which was convenient for visual analysis.

A wearable sweat electrochemical aptasensor based on the Ni-Co MOF nanosheet-decorated CNTs/PU film for monitoring of stress biomarker

Monitoring cortisol, a hormone released by the adrenal cortex in response to stress, is essential to evaluate the endocrine response to stress stimuli. While the current cortisol sensing methods require large laboratory settings, complex assay, and professional personnel. Herein, a novel flexible and wearable electrochemical aptasensor based on a Ni-Co metal-organic frameworks (MOF) nanosheet-decorated carbon nanotubes (CNTs)/polyurethane (PU) film is developed for rapid and reliable detection of cortisol in sweat. First, the CNTs/PU (CP) film was prepared by a modified wet spinning technology, and the CNTs/polyvinyl alcohol (PVA) solution was thermally deposited on the surface of CP film to form the highly flexible CNTs/PVA/CP (CCP) film with excellent conductivity. Then aminated Ni-Co MOF nanosheet prepared by a facile solvothermal method was conjugated with streptavidin and modified on the CCP film. Biofunctional MOF can effectively capture cortisol aptamer due to its excellent specific surface area. In addition, the MOF with peroxidase activity can catalytic oxidization of hydroquinone (HQ) by hydrogen peroxide (H₂O₂), which could amplify the peak current signal. The catalytic activity of Ni-Co MOF was substantially suppressed in the HQ/H₂O₂ system due to the formation of the aptamer-cortisol complex, which reduced the current signal, thereby realizing highly sensitive and selective detection of cortisol. The sensor has a linear range of 0.1-100 ng/mL and a detection limit of 0.032 ng/mL. Meanwhile, the sensor showed high accuracy for cortisol detection under mechanical deformation conditions. More importantly, the prepared MOF/CCP film based three-electrode was assembled with the polydimethylsiloxane (PDMS) substrate, and the sweat-cloth was used as the sweat collection channel to fabricate a wearable sensor patch for monitoring of cortisol in volunteers' sweat in the morning and evening. This flexible and non-invasive sweat cortisol aptasensor shows great potential for quantitative stress monitoring and management.

ZnS:Eu @ZIF-8: Selective formation of ZnS:Eu QDs within a zinc methylimidazole framework for chemical sensing applications

Light harvesting based on a microporous zeolite imidazole backbone (MOF) has attracted considerable interest as a fluorescent sensor for the detection of analytes. In this work, we have prepared a novel complex containing quantum dots of doped rare earth elements by a one-pot method. to be applied to the fluorescence detection of pollution hazards. Because of the solid framework, the prepared ZnS:Eu@ZIF-8 composite shows desirable fluorescence properties. The selectivity and sensitivity of ZnS:Eu@ZIF -8 to TNP, which has a detection limit of 0.19 μmol/L, is further investigated and its sensing mechanism is discussed by means of fluorescence lifetime measurements in combination with emission and UV spectra. It should also be noted that this is the first doped quantum dot to be encapsulated in a MOF to be used for the potential detection of phenolic compounds in the aqueous environment, while the framework remains in place and no structural changes have occurred.

Highly Tunable MOF Luminophores Featuring Anthracene Directed Assembly and Fluorescence Regulation

Metal-organic frameworks (MOFs) have been recognized as a potential platform for the development of tunable luminophores owing to their highly modulable structures and components. Herein, two MOF luminophores based on Cd(II) ions, 1,3,5-tri(4-pyridinyl)benzene (TPB), and 1,4-dicarboxybenzene (H₂BDC) were constructed. The directed assembly of the metal ions and organic linkers results in [Cd₂(BDC)₂(TPB)(H₂O)]·x(solvent) (MOF-1) featuring TPB-based blue fluorescence centered at 425 nm. By introducing anthracene as the structure directing agent (SDA) for assembly regulation, [Cd₂(BDC)(TPB)₂(NO₃)₂]·x(solvent) (MOF-2) was obtained, which reveals anthracene feeding-dependent high tunable emission in the 517-650 nm range. Detailed components, photophysical properties, and structural characteristics investigations of MOF-2 indicate the TPB and NO₃^- interactions as the origin of its redshifted emission compared with that of MOF-1. Furthermore, the fluorescence of MOF-2 was found to be regulatable by the anthracene feeding based on the SDA-determined crystallinity of the crystalline sample. All these results provided a unique example of the structural and fluorescence regulation of MOF luminophores.

Zn-MOFs composites loaded with silver nanoparticles are used for fluorescence sensing pesticides, Trp, EDA and photocatalytic degradation of organic dyes

The abuse of pesticides, antibiotics, organic solvents, etc., not only deteriorates the ecological environment, but even affects the normal development of organisms, posing a serious threat to global public health.Efficient and sensitive detection of pesticides, antibiotics, organic solvents and so on are very important, but also a challenge to scientists. By depositing Ag nanoparticles on the surface of Zn-MOF (1: {[Zn₂(bta)(bpy)(H₂O)₂]·2H₂O}_n), a new type of composite material (Ag@1) was successfully synthesized and analyzed by TEM, EDS, XPS, XRD, IR and other characterization methods. Ag@1 can serve as multi-response fluorescence sensor to detect pesticides (fluazinam (FLU) and emamectin benzoate (EMB)), Tryptophan (Trp) and Ethylenediamine (EDA). In particular, Ag@1 showed "turn-off" fluorescence sensing for FLU and EDA, and "turn-on" fluorescence sensing for EMB and Trp. It is worth mentioning that we further explored its analysis of FLU and Trp in real water samples and fetal bovine serum. The recoveries are satisfactory, 97.95 % - 102.39 % and 96.69 % - 101.85 %, respectively. In addition, the photocatalytic performance of Ag@1 was found to be excellent, the degradation rate of methylene blue (MB) reached 86 %, and its degradation mechanism was discussed.

Enhanced Luminescence of Dye-Decorated ZIF-8 Composite Films via Controllable D-A Interactions for White Light Emission

Metal-organic frameworks (MOFs) constructed by metal ions/clusters and organic linkers are used to encapsulate fluorescent guest species with aggregation-caused quenching (ACQ) effects to enhance fluorescence properties due to their porous structures and high specific surface areas. However, there would be a problem of matching between MOF pores and guest molecules' sizes. In this paper, amorphous ZIF-8 was modified by carboxyl functional groups (H₃BTC-ZIF-8) via introducing the 1,2,4-benzenetricarbonic acid (H₃BTC) ligand into the ZIF-8 sol system. Moreover, H₃BTC-ZIF-8 was used for the loading of organic fluorescent dyes rhodamine 6G (R6G) and coumarin 151 (C151) to prepare R6G/C151/H₃BTC-ZIF-8 composite films. A white-light-emitting composite film (R6G/C151/H₃BTC-ZIF-8) with CIE coordinates of (0.323, 0.347) was successfully prepared by compounding fluorescent dyes (R6G and C151) with H₃BTC-modified ZIF-8, whose photoluminescence quantum yield (PLQY) can reach 64.0%. It was higher than the PLQY of the composite films prepared by crystalline ZIF-8 (40.2%) or amorphous ZIF-8 without H₃BTC (48.0%) compounded with the same concentrations of dyes. The fluorescence enhancement was probably attributed to an increased amount of active sites of H₃BTC-modified ZIF-8 interacting with dyes C151 and R6G. This can form hydrogen bonds between H₃BTC-ZIF-8 and C151, and weak electron donor-acceptor (D-A) interactions between H₃BTC-ZIF-8 and R6G molecules, respectively, thus enhancing the interactions between dyes and ZIF-8 and reducing the ACQ effect existing between dye molecules. Therefore, this strategy could provide an important guidance to develop white-light-emissive materials.

A smartphone-assisted optosensing platform based on chromium-based metal-organic framework signal amplification for ultrasensitive and real-time determination of oxytetracycline

Ultrasensitive and onsite detection of oxytetracycline (OTC) is of vital significance for ensuring public health. Herein, a novel and versatile fluorescence biomimetic nanosensor, Mg,N-CDs@MIL-101@MIP, was elaborately tailored for the assay of OTC. MIL-101 with extraordinarily high surface area and porosity, as a favorable supporter, suppressed self-quenching of Mg,N-CDs and boosted mass transfer rate, realizing signal amplification. As an ultrasensitive signal transducer, high luminescent Mg,N-CDs yielded conspicuous fluorescence responses for OTC, enhancing the sensitivity of Mg,N-CDs@MIL-101@MIP. High-affinity imprinting sites further endowed Mg,N-CDs@MIL-101@MIP with superior anti-interference ability and reusability. Given prominent merits, Mg,N-CDs@MIL-101@MIP demonstrated a good linear range (0.05-40 μg mL^-1) with a lower limit of detection (16.8 ng mL^-1), supplying high accessibility to realize ultrasensitive and highly selective measurement of OTC in samples. Additionally, to attain precise onsite profiling of OTC, an intelligent sensing platform was developed by integrating Mg,N-CDs@MIL-101@MIP with a portable smartphone-assisted optical device. As both signal reader and analyzer, smartphone can instantly capture concentration-dependent fluorescent images and accurately digitize them, accomplishing quantitative analysis of OTC. More delightfully, the portable platform was utilized for visual determination of OTC in milk samples with satisfactory results, offering a promising tool for the high-performance onsite evaluation of food safety and environmental health.

Luminescent MOF-Based Nanofibers with Visual Monitoring and Antibacterial Properties for Diabetic Wound Healing

Diabetic wound healing remains as a serious challenge for medical circles that required continuous monitoring and effective management. Herein, the glucose oxidase/carbon dots@copper-metal-organic framework-based nanofibers (GOx/CDs@MOF NFs) were proposed as a multifunctional wound dressing, aiming to visually monitor wound pH and inhibit bacterial infection. In the diabetic wound microenvironment, the GOx/CDs@MOF NFs could convert endogenous glucose into hydroxyl radial (•OH) through the cascade catalytic reaction. In vivo and vitro experimental results confirmed that the GOx/CDs@MOF NFs could efficiently kill bacteria and promote wound healing. Additionally, CDs as a pH fluorescent indicator endowed GOx/CDs@MOF NFs with sensitive and reversible fluorescent sensing behavior to wound pH, and these visual images could also be captured by smartphones and transformed into RGB color mode (red, green, blue) values, allowing for onsite evaluation of the wound status. This multifunctional wound dressing provides a smart and effective solution for diabetic wound management and takes an immeasurable step toward the development of the next generation of digitally visualized wound dressings.

Hydrogen-Bond-Connected 2D Zn-LMOF with Fluorescent Sensing for Inorganic Pollutants and Nitro Aromatic Explosives in the Aqueous Phase

Herein, a novel luminescent Zn-LMOF, JLU-MOF109 ([Zn(PBBA)(H₂O)]·3DMF·2H₂O, PBBA = 4,4'-(2,6-pyrazinediyl)bis[benzoic acid], DMF = N,N-dimethylformamide), was successfully synthesized under solvothermal conditions. Zinc ions are connected by PBBA ligands to form two-dimensional (2D) layers, and the layers are further propped up through hydrogen-bonding interactions. JLU-MOF109 exhibits good sensitivity to inorganic pollutants, Fe³⁺ and Cr₂O₇^2-, as well as nitro aromatic explosives, 2,4,6-trinitrophenol and 2,4-dinitrophenol. JLU-MOF109 exhibits high K_sv (at 10⁴ M^-1 level) and low limit of detection values (∼10^-6 mol/L) for the abovementioned hazardous pollutants, which is better than a majority of previously reported MOF-based fluorescent sensors. With good stability in the aqueous phase, JLU-MOF109 can serve as a promising chemical sensor for pollutant detection in wastewater.

High-Performance Electrochemiluminescence of a Coordination-Driven J-Aggregate K-PTC MOF Regulated by Metal-Phenolic Nanoparticles for Biomarker Analysis

The elimination of aggregation-caused quenching of polycyclic aromatic hydrocarbons by metal-ligand coordination is of immense scientific interest in solid-state electrochemiluminescence (ECL) sensing. Herein potassium ion (K⁺)-mediated J-aggregate K-PTC MOF (PTCA, perylene-3,4,9,10-tetracarboxylic) was synthesized and employed to formulate an ECL immunosensor for biomarker detection. The coordination-driven aggregates are arranged in an end-to-end side mode, which overcomes the aggregation-caused quenching related to PTCA concentration. Compared with PTCA, K-PTC MOF shows a more stable ECL emission with an unprecedented red shift to 718 nm and is equipped with ECL activity for analytical applications at a voltage of -1.1 V. Considering the requirements of accurate detection, metal-phenolic bioactive nanoparticles (MPNPs) were synthesized for the construction of a sandwich sensing platform to realize the steady-state regulation of ECL. As proof of applicability, a constructive experiment was carried out with neuron-specific enolase (NSE), a marker of small cell lung cancer (SCLC), as a targeted analyte. With optimal requirements, the configuration can provide a detection range of 10 pg/mL to 50 ng/mL and a detection limit of 7.4 pg/mL, accompanied by sufficient practical analytical performance. Collectively, this paradigm provides a deeper understanding of the ECL characteristics of coordination-driven J-aggregation and provides more possibilities for the development of ECL patterns based on luminescent metal-organic frameworks.

Water-Stable Cd-MOF with fluorescent sensing of Tetracycline, Pyrimethanil, abamectin benzoate and construction of logic gate

Due to the indiscriminate abuse of pesticides and antibiotics has caused serious threats to the environment and human and animal bodies, the detection of antibiotics and pesticides has attracted widespread attention in recent years. Herein, a novel 2D Cd (II)-MOF, [Cd(L)_0.5(1,2-bimb)] (Cd-L-1,2-bimb), [H₄L = 1, 1'-ethylbiphenyl -3, 3', 5, 5'- tetracarboxylic acid, 1, 2-bimb = 1, 2-bis[(1H-imidazol-1-yl) methyl] benzene] is synthesized. Cd-L-1,2-bimb has excellent stability in different organic solvents and in the range of pH 1.1-12.5. Cd-L-1,2-bimb exhibits high selectivity, high sensitivity, and fast luminescent response to pesticides [pyrimethanil (PTH, LOD = 2.2 μM) and abamectin benzoate (AMB, LOD = 2.39 μM)] and antibiotic contaminants tetracycline (TET, LOD = 0.13 μM). Cd-L-1,2-bimb displays discriminative fluorescence when detecting AMB and PTH, and is an implication logic gate. Finally, the possible detection mechanism of Cd-L-1,2-bimb toward different pollutants is also further investigated. This MOF-based multifunctional sensor opens up new prospects for environmental monitors.