Porphyrin-Based Metal-Organic Framework Probe: Highly Selective and Sensitive Fluorescent Turn-On Sensor for M3+ (Al3+, Cr3+, and Fe3+) Ions

Multi-ion detection chemosensor based on rhodamine for turn-on fluorescence sensing and bioimaging of Fe3+, Al3+, Cr3+, and Hg2+ under different channels

A novel rhodamine-based multi-ion fluorescent sensor, RGN, was designed and synthesized for the highly selective detection of mercury ions (Hg2+) in ethanol and water systems, as well as trivalent cations (Fe3+, Al3+, and Cr3+) in acetonitrile and water systems using a two-step Schiff base reaction method. Nuclear magnetic titration experiments and theoretical calculations demonstrated that the sensor achieved the detection of the aforementioned metal ions through the fluorescence turn-on phenomenon induced by lactam ring-opening. Density functional theory (DFT) calculation results showed decreased HOMO-LUMO energy gaps and increased dipole moments, indicating the effective coordination of the sensor with the corresponding metal ions to form more stable complexes, thereby achieving detection objectives. Furthermore, the fluorescence turn-on sensor RGN exhibited relatively low detection limits, with limits of detection (LOD) for Fe3+, Al3+, Cr3+, and Hg2+ being 10.20 nM, 14.66 nM, 58.78 nM, and 73.33 nM, respectively. Finally, practical applications of sensor RGN in environmental water samples, L929 cells, and zebrafish were demonstrated, indicating its potential for detecting and tracking Fe3+, Al3+, Cr3+, and Hg2+ in environmental samples and biological systems, with prospects for biomedical applications in the diagnosis and treatment of heavy metal ion-induced diseases.

Water-Stable Ln-MOF as a multi-emitting luminescent sensor for the detection of metal ions and pharmaceuticals

The development of innovative multi-emission sensors for the rapid and accurate detection of contaminants is both vital and challenging. In this study, utilizing two rigid ligands (H3ICA and H4BTEC), a series of water-stable bimetallic organic frameworks (EuTb-MOFs) were synthesized. Luminescent investigations have revealed that EuTb-MOF-1 exhibits prominent multiple emission peaks, attributed to the distinctive fluorescence characteristics of Eu(III) and Tb(III) ions. Therefore, EuTb-MOF-1 efficiently recognized various metal ions and pharmaceutical compounds through 2D decoded maps. Fe3+ and Pb2+ exhibited significant quenching effects on the luminescence of EuTb-MOF-1, which were attributed to the internal filtering effect and the interaction between Lewis basic sites within EuTb-MOF-1 and Pb2+ ions, respectively. Furthermore, EuTb-MOF-1 demonstrated high sensitivity to sulfonamide antibiotics, with detection limits of 0.037 μM for SMZ and 0.041 μM for SDZ, respectively. In addition, EuTb-MOF-1 was immobilized to prepare MOF-based test strips, enabling direct visual detection of sulfonamides as a portable sensor. With excellent water stability, multi-responsive recognition capabilities, and high sensitivity to specific analytes, EuTb-MOF-1 is a promising candidate for environmental contaminant detection in aquatic systems.

Porphyrin Aluminum Metal-Organic Framework in Liquid Water, its Interaction with the Oxidized Organosulfur Compound Diethyl Sulfoxide, and its Sorption from Aqueous Solution

Oxidized organosulfur compounds and, in particular, sulfoxides are of interest as solvents in the semiconductor and pharmaceutical industry, environmental contaminants, and simulants in deactivation of chemical warfare agents. An experimental study is reported of the interaction of porphyrin aluminum metal-organic framework Al-MOF-TCPPH2 (Compound 2) with diethyl sulfoxide (DESO) in pure form and in aqueous solution. First, the suitability of Compound 2 as sorbent in aqueous solution was assessed; namely, its long-term stability (up to 15 days) in liquid water has been investigated at room temperature and under stirring. Here, a novel facile spectroscopic method has been used, a periodic micro-sampling of sorbent from suspension, followed by vacuum mini-filtration and an ex situ time-dependent attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) analysis. Next, the interaction of Compound 2 with pure liquid DESO under ambient conditions was investigated, which yields the stoichiometric adsorption complex (Al-MOF-TCPPH2)1(DESO)2 denoted Compound 3. In this adsorption complex, molecules of DESO interact with the OH group and carboxylate group of the sorbent. Then, the removal of DESO from Compound 3 was assessed, using facile treatment with warm water in the micro Soxhlet apparatus followed by the ATR FT-IR analysis. Finally, Compound 2 was tested in sorption of DESO from diluted aqueous solution. In the initial step, the sorption proceeds very quickly (in <1 min the concentration of DESO decreases by about 20%) followed by a much slower step. The maximum amount of adsorbed DESO corresponds to half of the amount adsorbed from pure DESO as found by the high-performance liquid chromatography-ultraviolet detection method. This adsorbed amount corresponds to 1 mol DESO adsorbate per mol of sorbent. Porphyrin aluminum metal-organic framework Compound 2 is promising for the removal of DESO from diluted aqueous solution, and it is of interest for the removal of similar oxidized organosulfur compounds.

A novel "ON-OFF-ON" colorimetric and fluorescence dual-signal sensing APAP based on TSPP-Fe3

Acetaminophen, also known as paracetamol (APAP), is a commonly used over-the-counter medication that is often used to treat headaches, toothaches, joint pain, muscle pain, and to lower body temperature. However, overdose can lead to liver damage, gastrointestinal distress, kidney damage, and cardiovascular disease. Therefore, it is very important to establish a method to quickly detect APAP. A novel "ON-OFF-ON" colorimetric and fluorescence dual-signal sensing system was constructed for the quantitative detection of APAP based on 5,10,15,20-tetrakis(4-sulphonatophenyl) porphyrin (TSPP) dual-signal probe. The absorbance and fluorescence intensity of TSPP respectively were quenched when Fe3+ was introduced into TSPP solution. At this point, the color of the corresponding solution changed from red to green. The absorbance and fluorescence intensity of TSPP respectively were restored when APAP was added to the TSPP-Fe3+ system. At this time, the color of the solution changed from green to colorless. Therefore, an "ON-OFF-ON" dual-signal sensing study of APAP were constructed using TSPP as the colorimetric and fluorescent probe. The proposed colorimetric sensing system had a wide linear range in the 13.12 mM ∼ 23.20 mM with 0.11 mM of limit of detection (LOD, S/N = 3). And the proposed fluorescence sensing system had a wide linear range in the 3.45 mM ∼ 12.50 mM and 41.67 mM ∼ 65.22 mM with 0.83 mM of limit of detection (LOD, S/N = 3). The dual-signal sensing system were applied to the APAP detection of real samples.

Highly sensitive and selective fluorescent "turn-on" sensor for Ag+ detection using MAPbBr3@PCN-221(Fe): An efficient Ag+-bridged energy transfer from perovskite to MOF

Metal ion-induced water pollution is attracting increasing public attention. Perovskite quantum dots and metal-organic frameworks (MOFs), owing to their outstanding properties, hold promise as ideal probes for detecting metal ions. In this study, a composite material, MAPbBr3@PCN-221(Fe), was prepared by encapsulating MAPbBr3 quantum dots with PCN-221(Fe), demonstrating high chemical stability and good reusability. The composite material shows a sensitive fluorescence turn-on signal in the presence of silver ions. The fluorescence intensity of the composite material exhibits a linear relationship with the concentration of Ag+ in the solution, with a low detection limit of 8.68 µM. Moreover, the fluorescence signal exhibits a strong selectivity for Ag+, enabling the detection of Ag+ concentration. This fluorescence turn-on signal originates from the Ag+-bridged energy transfer from the conductive band of MAPbBr3 to the excited state of the MOF, which is directly proportional to the concentration of silver ions. Simultaneously, this finding may open up a new possibility in artificial controlled energy transfer from perovskite to MOF for future development.

A Multifunctional CaII-EuIII Heterometallic Organic Framework with Sensing and Selective Adsorption in Water

With increasing global industrialization, it is urgent and challenging to develop multifunctional species for detection and adsorption in the environment. For this purpose, a novel anionic heterometallic organic framework, [(CH3)2NH2][CaEu(CAM)2(H2O)2]·4H2O·4DMF (CaEuCAM), is hydrothermally synthesized based on chelidamic acid (H3CAM). Single crystal analysis shows that CaEuCAM features two different oxygen-rich channels along the c-axis in which one CAM3- bridges two sextuple-coordinated Ca2+ and two octuple-coordinated Eu3+ with a μ4-η1: η1: η1: η1: η1: η1 new chelating and bridging mode. The characteristic bright red emission and superior hydrostability of CaEuCAM under harsh acidic and basic conditions benefit it by acting as a highly sensitive sensor for Fe3+ and 3-nitrophenol (3-NP) with extremely low LODs through remarkable quenching. The combination of experiments and theoretical calculations for sensing mechanisms shows that the competitive absorption and interaction are responsible for Fe3+-induced selective emission quenching, while that for 3-NP is the result of the synergism of host-guest chemistry and the inner filter effect. Meanwhile, the assimilation of negative charge plus channels renders CaEuCAM a highly selective adsorbent for methylene blue (MB) due to a synergy of electrostatic affinity, ion-dipole interaction, and size matching. Of note is the reusability of CaEuCAM toward Fe3+/3-NP sensing and MB adsorption besides its fast response. These findings could be very useful in guiding the development of multifunctional Ln-MOFs for sensing and adsorption applications in water media.

Porphyrin Metal-organic Framework Sensors for Chemical and Biological Sensing

Porphyrins and porphyrin derivatives have been intensively explored for a number of applications such as sensing, catalysis, adsorption, and photocatalysis due to their outstanding photophysical properties. Their usage in sensing applications, however, is limited by intrinsic defects such as physiological instability and self-quenching. To reduce self-quenching susceptibility, researchers have developed porphyrin metal-organic frameworks (MOFs). Metal-organic frameworks (MOFs), a unique type of hybrid porous coordination polymers comprised of metal ions linked by organic linkers, are gaining popularity. Porphyrin molecules can be integrated into MOFs or employed as organic linkers in the production of MOFs. Porphyrin-based MOFs are a separate branch of the huge MOF family that combines the distinguishing qualities of porphyrins (e.g., fluorescent nature) and MOFs (e.g., high surface area, high porosity) to enable sensing applications with higher sensitivity, specificity, and extended target range. The key synthesis techniques for porphyrin-based MOFs, such as porphyrin@MOFs, porphyrinic MOFs, and composite porphyrinic MOFs, are outlined in this review article. This review article focuses on current advances and breakthroughs in the field of porphyrin-based MOFs for detecting a variety of targets (for example, metal ions, anions, explosives, biomolecules, pH, and toxins). Finally, the issues and potential future uses of this class of emerging materials for sensing applications are reviewed.

Recent Developments in Porphyrin-Based Metal-Organic Framework Materials for Water Remediation under Visible-Light Irradiation

Access to clean drinking water is a basic requirement, and eliminating pollutants from wastewater is important for saving water ecosystems. The porous structure and surface characteristics of metal-organic frameworks (MOFs) can function as a perfect scaffold for removing toxic compounds from wastewater. Porphyrins are promising building blocks for constructing MOFs. Porphyrin-based metal-organic frameworks (P-MOFs) have been fabricated using porphyrin ligands, metal clusters, or ions. These materials can harvest light from a wide region of the solar spectrum, and their framework morphology and physicochemical properties can be controlled by changing their peripheral subunits or metal ions. These porous crystalline materials have generated interest because of their distinctive characteristics, including large permanent porosity, interesting surface morphology, broad conformational diversity, high photostability, and semiconducting nature. This article discusses the recent progress and usefulness of P-MOFs. The fabrication procedures of P-MOFs are discussed, followed by the adsorptive and photocatalytic removal of contaminants from wastewater. The relationships between the geometries of P-MOFs and their light-harvesting and charge-transfer mechanisms for the photocatalytic degradation of pollutants are highlighted. Finally, some future perspectives and obstacles in the photodegradation usage of P-MOFs are discussed, along with feasible research directions to standardize efficient photocatalysts for improved photodegradation for water treatment.

Remarkable water-mediated proton conductivity of two porous zirconium(IV)/hafnium(IV) metal-organic frameworks bearing porphyrinlcarboxylate ligands

Obtaining crystalline materials with high structural stability as well as super proton conductivity is a challenging task in the field of energy and material chemistry. Therefore, two highly stable metal-organic frameworks (MOFs) with macro-ring structures and carboxylate groups, Zr-TCPP (1) and Hf-TCPP (2) assembled from low-toxicity as well as highly coordination-capable Zr(IV)/Hf(IV) cations and the multifunctional linkage, meso-tetra(4-carboxyphenyl)porphine (TCPP) have attracted our strong interest. Note that TCPP as a large-size rigid ligand with high symmetry and multiple coordination sites contributes to the formation of the two stable MOFs. Moreover, the pores with large sizes in the two MOFs favor the entry of more guest water molecules and thus result in high H2O-assisted proton conductivity. First, their distinguished structural stabilities covering water, thermal and chemical stabilities were verified by various determination approaches. Second, the dependence of the proton conductivity of the two MOFs on temperature and relative humidity (RH) is explored in depth. Impressively, MOFs 1 and 2 demonstrated the optimal proton conductivities of 4.5 × 10-4 and 0.78 × 10-3 S·cm-1 at 100 °C/98 % RH, respectively. Logically, based on the structural information, gas adsorption/desorption features, and activation energy values, their proton conduction mechanism was deduced and highlighted.

An ultra-sensitive fluorescent probe for recognition of aluminum ions and its application in environment, food, and living organisms

The concentration of aluminum ions (Al3+) is closely related to the ecological environment, food safety, and human health, with excessive accumulation of Al3+ causing irreversible damage to both the ecological balance and human health. Therefore, a fluorescent probe ABHS, based on aminobenzoylhydrazide Schiff-base, was designed and synthesized in one step with a high yield. ABHS can form a 1:1 coordination complex with Al3+ in a pure water system. It exhibits ultra-sensitive and accurate detection of Al3+ even at low concentration of Al3+, with the detection limit of 6.7 nM. Furthermore, ABHS demonstrated significant enhancement of specific fluorescence for Al3+, with rapid response speed, good stability, and robust resistance to interference. Importantly, ABHS has shown excellent detection and imaging capabilities even in complex real environmental samples, food samples, and living organisms.

Two-Dimensional Nickel Porphyrinic Metal-Organic Framework-Modified Electrode for Electrochemical Sensing

Due to their highly exposed active sites and high aspect ratio caused by their substantial lateral dimension and thin thickness, two-dimensional (2D) metal-organic framework (MOF) nanosheets are currently considered a potential hybrid material for electrochemical sensing. Herein, we present a nickel-based porphyrinic MOF nanosheet as a versatile and robust platform with an enhanced electrochemical detection performance. It is important to note that the nickel porphyrin ligand reacted with Cu(NO3)2·3H2O in a solvothermal process, with polyvinylpyrrolidone (PVP) acting as the surfactant to control the anisotropic development of creating a 2D Cu-TCPP(Ni) MOF nanosheet structure. To realize the exceptional selectivity, sensitivity, and stability of the synthesized 2D Cu-TCPP(Ni) MOF nanosheet, a laser-induced graphene electrode was modified with the MOF nanosheet and employed as a sensor for the detection of p-nitrophenol (p-NP). With a detection range of 0.5-200 μM for differential pulse voltammetry (DPV) and 0.9-300 μM for cyclic voltammetry (CV), the proposed sensor demonstrated enhanced electrochemical performance, with the limit of detection (LOD) for DPV and CV as 0.1 and 0.3 μM, respectively. The outstanding outcome of the sensor is attributed to the 2D Cu-TCPP(Ni) MOF nanosheet's substantial active surface area, innate catalytic activity, and superior adsorption capacity. Furthermore, it is anticipated that the proposed electrode sensor will make it possible to create high-performance electrochemical sensors for environmental point-of-care testing since it successfully detected p-NP in real sample analysis.

Self-assembled nanovesicles based on chiral bis-H8-BINOL for Fe3+ recognition and secondary recognition of l-cysteine by 1 + 1 complex

A novel fluorescent "off" sensor, R-β-d-1, was obtained in high yield (91.2%) by using octahydronaphthol as a backbone, introducing an alkyne group at the 2-position, and linking azido-glucose via a click reaction. The sensor was analyzed by scanning electron microscopy and transmission electron microscopy and was found to be a self-assembled vesicle. AFM results showed that the fluorescence burst was extinguished by the addition of Fe3+, and the fluorescence was restored by the addition of cysteine. This is due to charge transfer within the molecular structure, resulting in the ICT effect and phototransfer of electrons (PET), as well as redshifting (from 331 nm to 351 nm) and quenching of the fluorescence. The self-assembled vesicles of the fluorescent sensor R-β-d-1 encapsulated Fe3+, but upon addition of cysteine, the vesicles of R-β-d-1-Fe3+ were also complexed with it, forming the R-β-d-1-Fe3+-l-Cys complex, at which point fluorescence gradually returned. Therefore, the fluorescence test of this probe showed that the lowest detection limit of iron ions was 1.67 × 10-7 mol L-1, and its complexation mode was in the form of 1 + 1. The novel probe formed by R-β-d-1-Fe3+ can be used for the fluorescence detection of cysteine.

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.

Synthesis of rare-earth metal-organic frameworks to construct high-resolution sensing array for multiplex anions detection, cell imaging and blood phosphorus monitoring

Accurate detection and differentiation of multiple anions is still a difficult problem due to their wide variety, structural similarity, and mutual interference. Hence, four rare-earth metal-organic frameworks (RE-MOFs) including Dy-MOFs, Er-MOFs, Tb-MOFs and Y-MOFs are successfully prepared by using TCPP as the ligand and rare-earth ions as the metal center via coordination chelation. It is found that 7 anions can light up their fluorescence. Thus, a high-resolution sensing array based on RE-MOFs nanoprobes is employed to differentiate these anions from intricate analytes in real-time scenarios. The distinctive host-guest response promotes the RE-MOFs nanoprobes to selectively extract the target anions from the complex samples. By taking advantage of the cross-response between RE-MOFs nanoprobes and anions, it allows to create an array for detecting target analytes using pattern recognition. Additionally, RE-MOFs nanoprobes also facilitate the quantitative analysis of these anions (PO43-, H2PO4-, HPO42-, F-, S2-, CO32- and C2O42-). More importantly, the exceptional effectiveness of this method has been demonstrated through various successful applications, including quality monitoring of 8 toothpaste brands, intracellular phosphate imaging, and blood phosphorus detection in mice with vascular calcification. These findings provide robust evidence for the efficacy and reliability of the RE-MOFs nanoprobes array for anion recognition.

A zinc-containing porphyrin aluminum MOF in sorption of diethyl sulfide vapor: mechanistic experimental and computational study

We report a mechanistic study of the interactions in the sorption of volatile organic sulfur compound (VOSC) diethyl sulfide (DES) by zinc porphyrin aluminum MOF (actAl-MOF-TCPPZn) compound 3. First, interactions were studied under dynamic conditions with the vapor of DES in flowing air, using in situ time-dependent ATR-FTIR spectroscopy in a controlled atmosphere with a new facile spectroscopic mini-chamber. The first binding site includes μ(O-H) and COO- groups as detected by characteristic peak shifts. Control experiments with a model compound, which lacks porosity and these groups, show no peak shifts. An additional insight was obtained by DFT computations using small clusters. The kinetics of sorption of DES by compound 3 is of the Langmuir adsorption model and pseudo-first order with rate constant robs = 0.442 ± 0.056 min-1. Sorption of DES under static conditions in saturated vapor results in stoichiometric adsorption complex [Al-MOF-TCPPZn]1(DES)4 characterized by spectroscopic, structural and gravimetric methods; the adsorbed amount is very high (381 mg g-1 sorbent). The repetitive sorption and desorption of DES are conducted, with facile regeneration. Finally, the mechanistic details were determined by Raman and photoluminescence (PL) spectroscopy using a confocal Raman microscope. Photoexcitation of compound 3 at 405 nm into the Soret band of the metalloporphyrin linker shows the characteristic PL peaks of Q-bands: the purely electronic Q(0-0) and first vibronic Q(0-1) bands. Upon interaction with DES, preferential quenching of PL from the Q(0-0) band occurs with a significant increase of the signal of the vibronic Q(0-1) band, reflecting bonding to the metalloporphyrin ring. Compound 3 is of interest to mechanistic studies of VOSCs, their removal from air, and optical chemo-sensing.

Interaction of a Porphyrin Aluminum Metal-Organic Framework with Volatile Organic Sulfur Compound Diethyl Sulfide Studied via In Situ and Ex Situ Experiments and DFT Computations

The study presents complementary experiments and quantum chemical DFT computations to reveal the molecular-level interactions of an advanced nanomaterial, porphyrin aluminum metal-organic framework (compound 2), with the volatile organic sulfur compound diethyl sulfide (DES). First, the intermolecular host-guest interactions during the sorption of DES were explored under dynamic conditions, using the vapor of DES in flowing air. The in situ time-dependent ATR-FTIR spectroscopy in a controlled atmosphere was significantly improved though the use of a new facilely built spectroscopic mini-chamber. The binding site of DES in compound 2 involves the μ(O-H) and COO- groups of the linker of the sorbent. Further, the chemical kinetics of the sorption of DES was investigated, and it follows the Langmuir adsorption kinetic model. That is, depending on the time interval, the process obeys either the pseudo-first- or pseudo-second-order rate law. For the Langmuir adsorption of the pseudo-first order, the rate constant is robs = 0.165 ± 0.017 min-1. Next, the interaction of compound 2 with the saturated vapor of DES yields the adsorption complex compound 3 [Al-MOF-TCPPH2]2(DES)7. The adsorbed amount of DES is very large at 36.5 wt.% or 365 mg/g sorbent, one of the highest values reported on any sorbent. The molecular modes of bonding of DES in the complex were investigated through quantum chemical DFT computations. The adsorption complex was facilely regenerated by gentle heating. The advanced functional material in this work has significant potential in the environmental remediation of diethyl sulfide and related volatile organic sulfur compounds in air, and it is an interesting target of mechanistic studies of sorption.

Highly Stable Rare Earth Metal-Organic Frameworks for Fluorescence Recognition of Folic Acid, Proton Conduction, and Magnetic Refrigeration

Four new isostructural rare earth metal-organic frameworks (RE-MOFs) were synthesized and full characterized, namely, {[(CH)2NH2]3[RE2(BTDBA)2(HCOO)]·5H2O·2DMF}n (H4BTDBA = (4',4'''-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis([1,1'-biphenyl]-3,5-dicarboxylic acid); RE = Eu (JXUST-34), Gd (JXUST-35), Tb (JXUST-36), and Dy (JXUST-37)). The single-crystal structures analysis shows that JXUST-34-37 are chain-based three-dimensional structures. Importantly, JXUST-34 exhibits excellent water, organic solvents, and acid-base stability, which can be used as a fluorescence sensor for folic acid and Al3+ with detection limits of 0.02 mM and 0.05 μM, respectively. The presence of free [(CH)2NH2]+ cations in the channels can engage the proton carrier during proton conduction. JXUST-34-37 display good proton conductivity, and the conductivities vary with relative humidity and temperatures, among which JXUST-37 has the highest conductivity of 9.66 × 10-3 S·cm-1 at 60 °C and 98% RH. The magnetic studies show that the -ΔSm of JXUST-35 reaches 16.13 J kg-1 K-1 at 2 K and ΔH = 7 T. JXUST-34-37 show multifunctional properties of fluorescence sensing, high proton conductivity, and magnetic refrigeration, which provides a new clue for the development of fluorescent-responsive, magnetic-refrigerant, and proton-conductive RE-MOF materials.

Solvothermal synthesis and device fabrication of a Eu3+-based metal-organic framework as a turn-on and blue-shift fluorescence sensor toward Cr3+, Al3+ and Ga3

A novel three-dimensional Eu³⁺-based metal-organic framework with the formula {[(CH₃)₂NH₂][Eu(BTDI)]·H₂O·DMF}_n (JXUST-25) was prepared by solvothermal method based on Eu³⁺ and 5,5'-(benzothiadiazole-4,7-diyl)diisophthalic acid (H₄BTDI) with benzothiadiazole (BTD) luminescent groups. Due to the presence of Eu³⁺ and organic fluorescence ligand, JXUST-25 displays turn-on and blue-shift fluorescence toward Cr³⁺, Al³⁺ and Ga³⁺ with limits of detection (LOD) of 0.073, 0.006 and 0.030 ppm, respectively. Interestingly, the alkaline environment can change the fluorescence of JXUST-25 toward Cr³⁺/Al³⁺/Ga³⁺ and the addition of HCl solution realizes the reversible change of the fluorescence of JXUST-25 toward Cr³⁺/Al³⁺/Ga³⁺. It is noteworthy that the fluorescent test paper and light-emitting diode lamp based on JXUST-25 can effectively detect Cr³⁺, Al³⁺ and Ga³⁺ by the visual changes. In addition, the turn-on and blue-shift fluorescence between JXUST-25 and M³⁺ ions may be caused by the host-guest interaction and the absorbance caused enhancement mechanism.

Theoretical Study of Charge Mobility in Crystal Porphine and a Computer Design of a Porphine-Based Semiconductive Discotic Liquid Mesophase

Organic semiconductors are the focus of numerous studies; they are used in electronic devices. Modern research involves the production of neuromorphic organic materials, including those based on liquid crystal materials. The purpose of this work involves the theoretical modeling of molecules (the "core with branches" type) to construct a discotic mesophase capable of performing the functions of a neuromorphic material. For this purpose, the conductivity of crystal porphine, which can act as the nucleus of a molecule of the "core with branches" type, was investigated. The Marcus theory charge mobility values for the hole and electron were 0.148 and 0.088 cm²/V·s, respectively (the MOO method for calculating transfer integrals), and 0.561 and 0.160 cm²/V·s (DIPRO method). Based on TD-HF (HF-3c level of theory) calculations, possible structures of molecules for the formation of a discotic mesophase are proposed.

Multifunctional nanomaterials and nanocomposites for sensing and monitoring of environmentally hazardous heavy metal contaminants

The applications of conventional sensors are limited by the long response time, high cost, large detection limit, low sensitivity, complicated usage and low selectivity. These sensors are nowadays replaced by Nanocomposite-based modalities and nanomaterials which are known for their high selectivity and physical and chemical properties. These nanosensors effectively detect heavy metal contaminants in the environment as the discharge of heavy metals into natural water as a result of human activity has become a global epidemic. Exposure to these toxic metals might induce many health-related complications, including kidney failure, brain injury, immune disorders, muscle paleness, cardiac damage, nervous system impairment and limb paralysis. Therefore, designing and developing novel sensing systems for the detection and recognition of these harmful metals in various environmental matrices, particularly water, is of extremely important. Emerging nanotechnological approaches in the past two decades have played a key role in overcoming environmentally-related problems. Nanomaterial-based fabrication of chemical nanosensors has widely been applied as a powerful analytical tool for sensing heavy metals. Portability, high sensitivity, on-site detection capability, better device performance and selectivity are all advantages of these nanosensors. The detection and selectivity have been improved using molecular recognition probes for selective binding on different nanostructures. This study aims to evaluate the sensing properties of various nanomaterials such as metal-organic frameworks, fluorescent materials, metal-based nanoparticles, carbon-based nanomaterials and quantum dots and graphene-based nanomaterials and quantum dots for heavy metal ions recognition. All these nano-architectures are frequently served as effective fluorescence probes to directly (or by modification with some large or small biomolecules) sense heavy metal ions for improved selectivity. However, efforts are still needed for the simultaneous designing of multiple metal ion-based detection systems, exclusively in colorimetric or optical fluorescence nanosensors for heavy metal cations.

Development of Red-Emissive Porphyrin Graphene Quantum Dots (PGQDs) for Biological Cell-Labeling Applications

Red and near-infrared emission is a highly desirable feature for fluorescent nanoparticles in biological applications mainly due to longer wavelengths more easily being able to deeply penetrate tissues, organs, skin, and other organic components, while less autofluorescence interference would be produced. Additionally, graphene quantum dots (GQDs) that contain unique optical and electrical features have been targeted for their use in cell labeling applications as well as environmental analysis. Their most desirable features come in the form of low toxicity and biocompatibility; however, GQDs are frequently reported to have blue or green emission light and not the more advantageous red/NIR emission light. Furthermore, porphyrins are a subgroup of heterocyclic macrocycle organic compounds that are also naturally occurring pigments in nature that already contain the desired red-emission fluorescence. Therefore, porphyrins have been used previously to synthesize nanomaterials and for nanoparticle doping in order to incorporate the red/NIR emission light property into particles that otherwise do not contain the desired emission light. Meso-tetra(4-carboxyphenyl)porphine (TCPP) is one type of porphyrin with a large conjugated π-electron system and four carboxyl groups on its exterior benzene rings. These two key characteristics of TCPP make it ideal for incorporation into GQDs, as it would design and synthesize red-emissive material as well as give rise to excellent water solubility. In this work, TCPP is used in tangent with cis-cyclobutane-1,2-dicarboxylic acid (CBDA-2), a biomass derived organic molecule, to synthesize "green" porphyrin-based graphene quantum dots (PGQDs) with red-emission. The obtained PGQDs were characterized by various analytical methods. Utilizing TEM, HRTEM, and DLS the size distribution of the particles was determined to be 7.9 ± 4.1, well within the quantum dot range of 2-10 nm. FT-IR, XPS, and XRD depicted carbon, nitrogen, and oxygen as the main elemental components with carbon being in the form of graphene and the main porphyrin ring of TCPP remaining present in the final PGQDs product. Lastly, absorption and fluorescence spectroscopy determined the excitation wavelength at 420 nm and the emission at 650 nm which was successfully utilized in the imaging of HeLa cells using confocal microscopy.

A new zinc-organic framework with 1D channel for constructing a ratiometric Al3+-selective sensor and four inputs INHIBIT logic gate

To develop Al³⁺ fluorescent sensor is significant because the abnormal levels of Al³⁺ in environment may pose great threat to human body. Herein, a novel metal-organic framework {Zn(Dpada)(Imdba)·H₂O}_n (Dpada = 3, 6-di(1H-imidazol-1-yl) pyridazine and Imdba = 2, 2'-iminodibenzoic acid), named Zn-MOF, has been architected with one-dimensional channel under hydrothermal conditions. Zn-MOF exhibits good thermal and solvent stability and can also keep structural integrity over the pH range of 5.0 - 9.0. Fluorescent experiments show that Zn-MOF has high selectivity and sensitivity towards Al³⁺ via ratiometric fluorescence signal changes (F_{470 nm}/F_{390 nm}) and the detection limit is evaluated to be 0.69 μM. In addition, Zn-MOF performs good recyclability in sensing of Al³⁺ with at least 5 cycles. Besides, an INHIBIT logic gate has been constructed with chemical ions (Al³⁺, Cr³⁺, Fe³⁺ and Hg²⁺) as input signals and emission ratio (F_{470 nm}/F_{390 nm}) as output signal. Significantly, Zn-MOF can be applied to tracing Al³⁺ using real water samples, presenting great potential in water quality monitoring application.

A Highly Selective MOF-Based Probe for Turn-On Luminescent Detection of Al3+, Cr3+, and Fe3+ in Solution and Test Paper Strips through Absorbance Caused Enhancement Mechanism

Trivalent metal ions (Cr³⁺, Al³⁺, and Fe³⁺) constitute a major section of the environmental pollutants, and their excess accumulation has a detrimental effect on health, so their detection in trace quantity has been a hot topic of research. A highly scalable 3D porous Zn-based luminescent metal-organic framework (MOF) has been synthesized by exploiting the mixed ligand synthesis concept. The strategic selection of an aromatic π-conjugated organic linker and N-rich spacer containing the azine functionality as metal ion binding sites immobilized across the pore spaces, have made this MOF an ideal turn-on sensor for Al³⁺, Cr³⁺, and Fe³⁺ ions with very high sensitivity, selectivity, and recyclability. An in-depth study revealed absorbance caused enhancement mechanism (ACE) responsible for such turn-on phenomena. In order to make the detection process straightforward, convenient, portable, and economically viable, we have fabricated MOF test paper strips (the MOF could be simply immobilized onto the paper strips) for naked eye visual detection under UV light, which, thus, manifests its potential as a real-time smart sensor for these trivalent ions.

Stable terbium metal-organic framework with turn-on and blue-shift fluorescence sensing for acidic amino acids (L-aspartate and L-glutamine) and cations (Al3+ and Ga3+)

A terbium-based metal-organic framework, namely {[Tb₂(ADIP)(H₂ADIP)(HCOOH)(H₂O)₂]·2DMF·2H₂O}_n (Tb-MOF, H₄ADIP = 5,5'-(anthracene-9,10-diyl) diisophthalic acid), was synthesized and characterized. The single-crystal structure analysis shows that the Tb-MOF crystallizes in the C₂/_C space group in the monoclinic system and its asymmetric unit contains two Tb^III ions, one ADIP^4-, one H₂ADIP^2-, one coordinating formic acid and two coordination water molecules. Tb-MOF has a three-dimensional porous structure with a porosity of 41.5%. Tb-MOF is a highly selective and sensitive fluorescence turn-on and blue-shift sensor for L-aspartate (Asp), L-glutamine (Glu), Al³⁺ and Ga³⁺with detection limits of 0.25, 0.23, 0.069 and 0.079 μM, respectively. Experimental studies and theoretical calculations show that the sensing process is mainly attributed to the energy transfer and the absorbance caused enhancement (ACE) mechanism. Therefore, Tb-MOF is a good multi-response fluorescence sensor for acidic amino acids and Al³⁺, Ga³⁺cations.

Colorimetric assay based on peroxidase-like activity of dodecyl trimethylammonium bromide-tetramethyl zinc (4-pyridinyl) porphyrin for detection of organophosphorus pesticides

A simple and sensitive colorimetric assay for detecting organophosphorus pesticides (OPs) was developed based on 3,3',5,5'-tetramethylbenzidine (TMB)/hydrogen peroxide (H₂O₂)/dodecyl trimethylammonium bromide (DTAB)-tetramethyl zinc (4-pyridinyl) porphyrin (ZnTPyP). In this system, based on the peroxidase-like activity of DTAB-ZnTPyP, H₂O₂ decomposes to produce hydroxyl radicals, which oxidize TMB, resulting in blue oxidation products. The OPs (trichlorfon, dichlorvos, and thimet) were first combined with DTAB-ZnTPyP through electrostatic interactions. The OPs caused a decrease in the peroxidase-like activity of DTAB-ZnTPyP due to spatial site blocking. At the same time, π-interactions occurred between them, and these interactions also inhibited the oxidation of TMB (652 nm), thus making the detection of OPs possible. The limits of detection for trichlorfon, dichlorvos, and thimet were 0.25, 1.02, and 0.66 μg/L, respectively, and the corresponding linear ranges were 1-35, 5-45, and 1-40 μg/L, respectively. Moreover, the assay was successfully used to determine OPs in cabbage, apple, soil, and traditional Chinese medicine samples (the recovery ratios were 91.8-109.8%), showing a great promising potential for detecting OPs also in other complex samples.

A julolidine-chalcone-based fluorescent probe for detection of Al3+ in real water sample and cell imaging

A fluorescent probe 1 based on julolidine-chalcone derivative, which can specifically recognize aluminum ion with high selectivity and anti-interference, was developed. Probe 1 has good fluorescence stability and can detect Al³⁺ with turn-on fluorescence in a wide pH range of 4.0-9.0. The probe has good repeatability for the detection of Al³⁺ and fluorescence turn-on and off can be repeated with the alternate Al³⁺ and EDTA. The sensing mechanism is speculated that Al³⁺ will coordinate with hydroxyl oxygen and carbonyl oxygen on the probe through in situ ¹H NMR and HRMS combing with Job's plot. The probe can also detect Al³⁺ in actual water samples and applied to monitor Al³⁺ in biological system.

A novel active mitochondrion-selective fluorescent probe for the NIR fluorescence imaging and targeted photodynamic therapy of gastric cancer

The annual morbidity and mortality due to gastric cancer are still high across the world, posing a serious threat to public health. Improving the diagnosis rate of gastric cancer and exploring new treatments are urgent issues in the clinical field. In recent years, photosensitizer (PS)-based photodynamic therapy (PDT) has proven to be an effective cancer treatment strategy and can be used to treat a variety of cancers. Developing PSs with tumor-targeting ability and high singlet oxygen yield (Φ(¹O₂)) is the key to improving the PDT effect. Herein, we developed a novel diagnosis and treatment system (Cy₁₃₉₅-NPs). Our active thio-photosensitizer is based on the sulfur substitution strategy as it can reduce the S1-T1 energy gap, which can promote the process of intersystem crossing (ISC), thus resulting in high ROS generation efficiency. Cy₁₃₉₅-NPs exhibited stable spectral characteristics, satisfactory biocompatibility and high ¹O₂ yield under laser irradiation due to the introduction of the sulfur atom. In cellular studies, Cy₁₃₉₅-NPs could specifically target MKN45 cells via integrin α_vβ₃-mediated cRGD endocytosis and selectively aggregate in the mitochondria. Cy₁₃₉₅-NPs had no obvious cytotoxicity for MKN45 cells and exerted obvious phototoxicity due to the production of ¹O₂ under laser irradiation. The in vivo results showed that the fluorescence signal from the tumor site was obviously enhanced in 16-48 h, and Cy₁₃₉₅-NPs could selectively target solid tumors with a retention time of about 32 h. Under laser irradiation, Cy₁₃₉₅-NPs significantly inhibited tumor growth and led to significant tumor suppression and apoptosis. In summary, the developed Cy₁₃₉₅-NPs could actively target tumors and exert mitochondrial selectivity, showing an excellent fluorescence imaging effect. Under the irradiation of an 808 nm laser, Cy₁₃₉₅-NPs achieved good inhibition of gastric cancer cells both in vitro and in vivo, thus displaying the functions of tumor targeting, mitochondrial selectivity, fluorescence imaging and tumor inhibition. Our strategy provides a new diagnostic and treatment method for gastric cancers in clinical settings.

Two bis-ligand-coordinated Zn(ii)-MOFs for luminescent sensing of ions, antibiotics and pesticides in aqueous solutions

Two organometallic complexes with two and three-dimensional architectures were constructed by using multiple ligands and Zn(ii) ions: [Zn₃(BTC)₂(DTP)₄(H₂O)₂]·(H₂O)₄ (Zn-1) (BTC = benzene-1,3,5-tricarboxylic acid and DTP = 3,5-di(1,2,4-triazol-1-yl)pyridine) and [Zn₂(NTD)₂(DTP)] (Zn-2) (NTD = 1,4-naphthalenedicarboxylic acid). The as-prepared complexes were characterized by single-crystal X-ray diffraction (SCXRD), elemental analysis, powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and fluorescence analysis. Fluorescence sensing tests revealed that the two complexes are effective, sensitive and selective toward cationic Fe³⁺ and anionic MnO₄ ^- and Cr₂O₇ ^2-. During the antibiotic sensing process, cefixime (CFX) for Zn-1 and nitrofurantoin (NFT) for Zn-2 exhibited the highest quenching efficiencies. For sensing pesticides, the highest quenching efficiencies were exhibited by imidacloprid (IMI) toward Zn-1 and Zn-2. The fluorescence quenching of the complexes that was induced by antibiotics, pesticides and MnO₄ ^- was attributed to both the inner filter effect (IFE) and the fluorescence resonance energy transfer (FRET) effect.

A Benzothiadiazole-Based Eu3+ Metal-Organic Framework as the Turn-On Luminescent Sensor toward Al3+ and Ga3+ with Potential Bioimaging Application

The design and preparation of novel multifunctional lanthanide metal-organic frameworks (Ln-MOFs) have been arisen widespread attention. In particular, Ln-MOFs have shown great luminescence potential in chemical sensing. Herein, a new benzothiadiazole-based Eu-MOF {[(CH₃)₂NH₂][Eu(BTDB)₂]·2H₂O}_n (JXUST-11) was obtained based on 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid (H₂BTDB), which exhibits a chain-based three-dimensional framework. Moreover, JXUST-11 is considered as a photoluminescent sensor to identify Al³⁺ and Ga³⁺ ions by fluorescence enhancement with the detection limits of 2.9 and 10.2 ppm, severally. Importantly, Al³⁺ and Ga³⁺ can be discerned with the naked eye by color change under a natural lamp. In addition, a portable MOF film based on JXUST-11 was developed for Al³⁺ and Ga³⁺ detection. This is the first Ln-MOF that can be employed as a naked-eye fluorescent probe to identify Ga³⁺. Interestingly, JXUST-11 is also capable of detecting Al³⁺ and Ga³⁺ in living cells.

Recent progress on porous MOFs for process-efficient hydrocarbon separation, luminescent sensing, and information encryption

Metal-organic frameworks (MOFs), as an emerging class of porous materials, excel in designability, regulatability, and modifiability in terms of their composition, topology, pore size, and surface chemistry, thus affording a huge potential for addressing environment and energy-related challenges. In particular, MOFs can be applied as porous adsorbents for the purification of industrially important hydrocarbons through certain process-efficient separation schemes based on selectivity-reversed adsorption and multicomponent separation. Moreover, the vast combination possibilities and controllable and engineerable luminescent units of MOFs make them a versatile platform to develop functionally tailored materials for luminescent sensing and optical data encryption. In this feature article, we summarize the recent progress in the use of porous MOFs for the separation and purification of acetylene (C₂H₂) and ethylene (C₂H₄) based on selectivity-reversed adsorption and multicomponent separation strategies. Moreover, we highlight the advances over the past three years in the field of MOF-based luminescent materials for thermometry, turn-on sensing, and information encryption.

Sensing and photocatalytic properties of a new 3D Co(ii) coordination polymer based on 1,1′-di(p-carboxybenzyl)-2,2′-biimidazole

One novel 3D interpenetrated Co(ii) CP acts as multi-functional chemosensors in detection of Fe3+, Cr2O72−, CrO42− and nitrofurantoin and is an effective and stable photocatalyst and displays excellent photo-catalytic properties.

Three-dimensional Cd(ii) porphyrin metal–organic frameworks for the colorimetric sensing of Electron donors

Three MOFs with metalloporphyrin lined, large square 1D channels were used as colorimetric sensors for electron donors. Exposure to amine vapours caused a redshift of the Soret absorption bands of the metalloporphyrin.

Selective luminescent sensing of metal ions and nitroaromatics over a porous mixed-linker cadmium(ii) based metal–organic framework

A potential luminescent sensor based on porous metal organic framework for the detection of metal ions (Al3+, Fe3+ or Cr3+) and nitro-explosive, 2,4,6-tri-nitrophenol has been discovered. MOF is capable of detecting aqueous phase analyte through luminescent sensing.

A novel 2D metal–organic framework probe: a highly sensitive and visual fluorescent sensor for Al3+, Cr3+ and Fe3+ ions

A novel 2D MOF Tb-DBA was constructed. Tb-DBA could detect Al3+, Cr3+ and Fe3+ ions rapidly, sensitively, selectively, reversibly and visually. Tb-DBA represents a promising material for the quick detection of metal ions in aqueous solution.

Construction of a Luminescent Cadmium-Based Metal-Organic Framework for Highly Selective Discrimination of Ferric Ions

Fluorescent metal–organic frameworks (MOFs) are ideal materials for sensors because of their adjustable pore size and functional groups, which provide them with favorable metal ion selective recognition. In this paper, a new cadmium-based MOF was synthesized using Cd(NO₃)₂·4H₂O and 3,3′,5,5′-biphenyltetracarboxylic acid by solvothermal method. CdBPTC owned three types of channels with dimensions of approximately 8.4 × 8.3 Å, 6.0 × 5.2 Å, 9.7 × 8.4 Å along a, b, and c axis, respectively. This MOF has high selectivity to ferric ions and shows excellent anti-inference ability toward many other cations. The results indicate that the fluorescence quenching efficiency of CdBPTC is close to 100% when the concentration of Fe³⁺ reaches 1.0 × 10⁻³ mol·L⁻¹. Moreover, the luminescent intensity at 427 nm presents a linear relationship at a concentration range of 2.0 × 10⁻⁴~7.0 × 10⁻⁴ mol·L⁻¹, which can be quantitatively expressed by the linear Stern–Volmer equation I₀/I = 8489 [Fe³⁺] − 0.1400, which is comparable to the previously reported better-performing materials. Competitive energy absorption and ion exchange may be responsible for the variation in fluorescence intensity of CdBPTC in different Fe³⁺ concentrations.

A multifunctional benzothiadiazole-based fluorescence sensor for Al3+, Cr3+ and Fe3+

A benzothiadiazole-based Zn^II MOF (JXUST-3) has been synthesized, which is a good multifunctional chemosensor for the detection of Al³⁺, Cr³⁺ and Fe³⁺.

A multi-responsive MOF-based fluorescent probe for detecting Fe3+, Cr2O72− and acetylacetone

A novel ZnII-based MOF can selectively and sensitively recognize Fe3+, Cr2O72− and acetylacetone, simultaneously.