Stable Indium Pyridylcarboxylate Framework with Highly Selective Adsorption of Cationic Dyes and Effective Nitenpyram Detection

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.

An upconverted nanoparticle-porphyrin metal-organic framework platform for near-infrared detection of nitenpyram

A ratiometric nitenpyram (NIT) upconversion luminescence sensor UCNPs-PMOF was fabricated from a metal-porphyrin organic framework (PMOF) and pretreated UCNPs. The reaction between NIT and the PMOF releases the H₂TCPP (5,10,15,20-tetracarboxyl phenyl) porphyrin ligand, which enhances the absorption of the system at 650 nm, and reduces the upconversion emission intensity of the sensor at 654 nm through a luminescence resonance energy transfer (LRET) mechanism, thus achieving the quantitative detection of NIT. The detection limit was 0.21 μM. Meanwhile, the emission peak of UCNPs-PMOF at 801 nm does not change with the concentration of NIT, and the emission intensity ratio (I_{654 nm}/I_{801 nm}) is used to achieve the ratiometric luminescence detection of NIT, and the detection limit is 0.22 μM. UCNPs-PMOF has good selectivity and anti-interference to NIT. In addition, it has a good recovery rate in actual sample detection, which indicates that it has high practicability and reliability in NIT detection.

Selective detection of nitenpyram by silica-supported carbon quantum dots

In this study, a fluorescent sensor of nitrogen-doped carbon quantum dots (N-CQDs) and silica gel hybrid was developed for the quantitative detection of nitenpyram, a toxic neonicotinoid existing in groundwater and/or surface water.The prepared N-CQDs@SiO₂ sensor exhibited remarkable sensing selectivity and sensitivity towards nitenpyram among the four pesticides and six metal ions. A prominent fluorescence quenching of N-CQDs@SiO₂ at 445 nm was observed in the presence of nitenpyram with a linear response range of 0-300.0 mg L^-1 and an estimated limit of detection of 1.53 mg L^-1. The main cause for selective sensing is that nitenpyram absorbs the excitation light of N-CQDs@SiO₂, leading to fluorescence quenching of the sensor through the inner filter effect.

A luminescent Eu@SOF film fabricated by electrophoretic deposition as ultrasensitive platform for styrene gas quantitative monitoring through fluorescence sensing and ANNs model

Styrene is a harmful gas widely existing in the air, which can damage human organs. Therefore, it is very crucial to develop a sensitive, portable and simple sensor for monitoring styrene. Herein, we design and fabricate a luminescent Eu@TMA-ME/FTO film (F) through EPD method. F emits bright red light of Eu(III) ions and shows superior fluorescence response to styrene gas as a sensor, which enable real-time and quantitative monitoring for styrene gas. More importantly, F exhibits a linear response to styrene gas in a wide concentration range of 10^-7 to 10^-2 M and a low DL with 0.20 ppm. The efficient PET process to styrene induced by ME and the competitive absorption between styrene and F are responsible for the sensing mechanism. Besides, the detection of styrene solution is also investigated in deionized water, tap water and river water. For the further application, an intelligent ANNs model has been constructed to process the fluorescence sensing results, which can convert fluorescence sensing images to the concentration of styrene gas. The data demonstrates that ANNs model can accurately monitor the concentration of styrene gas via deep ML without tedious data processing.

Anionic lanthanide metal-organic frameworks with magnetic, fluorescence, and proton conductivity properties and selective adsorption of a cationic dye

Two novel microporous anionic lanthanide metal-organic frameworks (Ln-MOFs), namely {[(CH₃)₂NH₂][Ln(bptc)]·2H₂O}_n (Ln = Gd (1) and Dy (2), H₄bptc = biphenyl-3,3',5,5'-tetracarboxylic acid) with a new 4,8-connected topology have been synthesized and structurally characterized. Ln-MOF 1 shows a significant magnetocaloric effect with -ΔSmaxm = 26.37 J kg^-1 K^-1 at 2 K for ΔH = 7 T, and a high proton conductivity of 1.02 × 10^-4 S cm^-1 at 323 K and 90% RH. Moreover, Ln-MOF 1 shows specific selective adsorption of the cationic dye Rhodamine B. Ln-MOF 2 exhibits field-induced slow magnetic relaxation with an energy barrier (U_eff) of 48.19 K, characteristic emission of Dy³⁺, and selective adsorption of Rhodamine B. Therefore, 2 is a multifunctional Ln-MOF with magnetic, fluorescence and selective adsorption properties.

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.

A hydrostable CuII coordination network prepared hydrothermally as a "turn-on" fluorescent sensor for S2- and a selective adsorbent for methylene blue

The effective monitoring of water pollution and further purification are pressing yet challenging issues for guaranteeing the health of human beings and the stabilization of ecological systems. For this purpose, the development of efficient sensing and adsorption materials as a result of supramolecular interactions, including coordination and H-bonding etc., have been attracting increasing attention. With the aid of a coordination-driven self-assembly strategy, a new nonporous 2D CuII coordination network, [Cu2L(H2O)2]n (donated as CuCP), based on H4L, where H4L = 4-(4-(3,5-di-carboxy-pyridin-4-yl)phenyl)pyridine-2,6-dicarboxylic acid, was afforded hydrothermally. Structural analysis indicated that CuCP featured a wrinkled network similar to the ancient Chinese folding screens and constructed by the fully deprotonated ligand L4- with the coordination mode of bis(μ2-η1:η1:η2) and penta-coordinated Cu2+, which could be further upgraded to a supramolecular 3D framework as a result of the synergism of multiple C-H⋯O hydrogen bonds. The hydrostability of CuCP could be maintained within a wide pH range from 2 to 12 as verified by PXRD determination, endowing it with potential environmental applications. Thanks to the combination of the soft Lewis acidity of Cu2+ and its large conjugated structure, CuCP could be used as a turn-on fluorescence sensor for S2- and exhibited a different fluorescence response when Na2S, (NH4)2S or H2S were incorporated, even in actual water samples. The sensing mechanisms were disclosed in detail by the combination of experiments and density functional theory (DFT) calculations. Furthermore, CuCP was shown to be a selective and recoverable adsorbent with a maximum adsorption capacity of 379 mg g-1 in 60 minutes for methylene blue (MB). The adsorption mechanism could be a combination of π⋯π stacking, n⋯π interaction, aggregation effects and Soft and Hard Acid-Base theory (HSAB). The results presented herein open up new perspectives for CuII species in environmental applications.

Indium metal-organic frameworks based on pyridylcarboxylate ligands and their potential applications

Indium metal-organic frameworks (In-MOFs) based on pyridylcarboxylate ligands represent a subclass of MOFs featuring diverse structures, a high stability, and various properties. This review discusses the different aspects of In-MOFs including their design, synthesis and structures as well as their typical potential applications in adsorption and separation, catalysis, and chemical sensors. Importantly, the effect of pyridine on the properties and stability of frameworks has been carefully studied. The introduction of a pyridine group not only significantly enriches clusters of In3+ ions, but also enables flexible, controllably synthesized ionic or neutral frameworks to be fabricated. Based on this, we suggest that this type of In-metal organic framework (MOF) should receive more attention in the field of MOF design.