Lanthanide Metal-organic Frameworks Research Articles

Three-Dimensional Neodymium Metal–Organic Framework for Catalyzing the Cyanosilylation of Aldehyde and the Synthesis of 2,3-Dihydroquinazolin-4(1H)-one Derivatives

In this work, a novel 3D lanthanide metal–organic framework (Ln-MOF) Nd-cdip (H4cdip = 5,5′-carbonyldiisophthalic acid) was successfully synthesized, which could be used as an efficient heterogeneous catalyst for cyanosilylation and the synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives at room temperature based on the Lewis acid sites in the channels of the MOF. Moreover, Nd-cdip had an excellent turnover number (500) for catalyzing cyanosilylation in no solvent condition. Nd-cdip could be reused in both of the above-mentioned reactions at least five times without a significant decrease in yield. The possible mechanism of cyanosilylation catalyzed by Nd-cdip was studied by using the luminescence properties of Tb-cdip, which has the same structure and functions as Nd-cdip. Furthermore, both reactions catalyzed by Nd-cdip were fitted to zero-order dynamics.

Near-infrared magnetic core-shell nanoparticles based on lanthanide metal-organic frameworks as a ratiometric felodipine sensing platform

Felodipine is an effective drug to treat hypertension, but its abuse can cause bardycardia. It is significant to develop highly sensitive detection platform for felodipine to enable the efficient treatment of hypertension diseases. In this work, to highly efficiently detect felodipine, multi-emission near-infrared (NIR) hierarchical magnetic core-shell lanthanide-MOF nanoparticles, namely Nd-MOF@Yb-MOF@SiO2@Fe3O4 (NIR-1), has been synthesized by layer-by-layer (LBL) method. LBL method can adjust the optical properties of NIR-1 and expose more active sites to improve sensitivity in detection process. NIR-1 has near-infrared luminescence emission, which can efficiently avoid the interference of autofluorescence in biological tissues. Photo-luminescent (PL) experiments also reveal that NIR-1 could be used as a near-infrared ratiometric luminescent sensor for felodipine detection with high selectivity and sensitivity, the low of detection limit (LOD) is 6.39 nM in felodipine detection, which is also performed using real biological samples. In addition, NIR-1 can be used as a ratiometric thermometer could also be applied in the temperature sensing from 293 K to 343 K. Finally, detection mechanisms for felodipine and temperature sensing performance based on near-infrared (NIR) emission were also investigated and discussed in detail.

Tetra-Nuclear Cluster-Based Lanthanide Metal-Organic Frameworks as White Phosphor, Information Encryption, Self-Calibrating Thermometers, and Fe2+ Sensors.

The application of one kind of metal-organic framework (MOF) material used in multiple fields is one of the most interesting research topics. In this work, four new tetra-nuclear cluster-based lanthanide metal-organic frameworks (LnMOFs) [Ln2(BTDB)3(DMA)(phen)]n (Ln = Tb TbMOF, Eu EuMOF, Gd GdMOF, Tb1.830Eu0.170 Tb,EuMOF, 3,5-bis(trifluoromethyl)-4',4″-dicarboxytriphenylamine = H2BTDB, 1,10-phenanthroline = phen) are obtained based on the ligand of H2BTDB that is synthesized in our laboratory, and the precise single-crystal structure of H2BTDB is obtained for the first time. The white phosphor was obtained by facilely hybridizing two components of the orange-yellow emission phosphor of Tb,EuMOF and the blue luminescence material of triphenylamine according to the trichromatic theory. At the same time, TbMOF, EuMOF, Tb,EuMOF, and the white phosphor can be used for information encryption, demonstrating their potential application in the field of anti-counterfeiting. Tb,EuMOF is also a multi-mode and self-calibrating thermometer within a broad temperature range of 110-300 K. Further studies show that EuMOF is a rapid response sensor for Fe2+, with a very low limit of detection of 2.0 nM, which is much lower than the national standards for Fe2+ (GB 5749-2005, 5.357 μM). It can achieve strong anti-interference detection of Fe2+ in actual samples of tap water and lake water. In addition, EuMOF can also be made into an easy-to-use sensing device of test paper for real-time and visual sensing of Fe2+.

Rational design of core-shell Ln-MOF hierarchitecture for ratiometric fluorescent sensing and bioimaging for phosphate or ATP

Mixed hierarchical lanthanide metal-organic framework (Ln-MOF) with core-shell structure has been acquired via a solution-mediated epitaxial growth method, retaining the spatially segregated structure of network and domain fluorescence property. The excellent heterostructured characteristics of Ln-MOFs enable the effective electron modulation, multiple energy transfer and thereby remarkably increase recognizing and sensing capacity in phosphate (Ps) or adenosine triphosphate (ATP). Ln3+ centers coupled with Ps or ATP could trigger a decrease in fluorescence of Ln3+, and further interrupt original fluorescence intensity ratio of Tb3+/Eu3+ (I545/I616) to shape the ratiometric fluorescent register. The optimized Tb/Eu-MOF with Tb/Eu ratio of 1:1 presented good linearity responsive to Ps and ATP with lower detection limit of 84.1 nM and 121.4 nM, respectively. Meanwhile, the interference and toxicity experiments have confirmed its high selectivity and high biocompatibility. Thus, the probe could be applied to detect Ps in real environmental water and biologically imaging ATP in Hela cells. This has provided a new strategy to construct Ln-system heterojunction with multiplexed luminescence selectivity and sensitivity in substance detection.

The Effect of Linker-to-Metal Energy Transfer on the Photooxidation Performance of an Isostructural Series of Pyrene-Based Rare-Earth Metal-Organic Frameworks.

The tetratopic linker, 1,3,6,8-tetrakis(p-benzoic acid)pyrene (H4 TBAPy) along with rare-earth (RE) ions is used for the synthesis of 9 isostructures of a metal-organic framework (MOF) with shp topology, named RE-CU-10 (RE = Y(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III), and Lu(III)). The synthesis of each RE-CU-10 analogue requires different reaction conditions to achieve phase pure products. Single crystal X-ray diffraction indicates the presence of a RE9 -cluster in Y- to Tm-CU-10, while a RE11 -cluster is observed for Yb- and Lu-CU-10. The photooxidation performance of RE-CU-10 analogues is evaluated, observing competition between linker-to-metal energy transfer versus the generation of singlet oxygen. The singlet oxygen produced is used to detoxify a mustard gas simulant 2-chloroethylethyl sulfide, with half-lives ranging from 4.0 to 5.8min, some of the fastest reported to date using UV-irradiation and < 1 mol% catalyst, in methanol under O2 saturation.

Ortho Effects of Tricarboxylate Linkers in Regulating Topologies of Rare-Earth Metal-Organic Frameworks.

A linker design strategy is developed to attain novel polynuclear rare-earth (RE) metal-organic frameworks (MOFs) with unprecedented topologies. We uncover the critical role of ortho-functionalized tricarboxylate ligands in directing the construction of highly connected RE MOFs. The acidity and conformation of the tricarboxylate linkers were altered by substituting with diverse functional groups at the ortho position of the carboxyl groups. For instance, the acidity difference between carboxylate moieties resulted in forming three hexanuclear RE MOFs with novel (3,3,3,10,10)-c wxl, (3,12)-c gmx, and (3,3,3,12)-c joe topologies, respectively. In addition, when a bulky methyl group was introduced, the incompatibility between the net topology and ligand conformation guided the co-appearance of hexanuclear and tetranuclear clusters, generating a novel 3-periodic MOF with a (3,3,8,10)-c kyw net. Interestingly, a fluoro-functionalized linker prompted the formation of two unusual trinuclear clusters and produced a MOF with a fascinating (3,8,10)-c lfg topology, which could be gradually replaced by a more stable tetranuclear MOF with a new (3,12)-c lee topology with extended reaction time. This work enriches the polynuclear clusters library of RE MOFs and unveils new opportunities to construct MOFs with unprecedented structural complexity and vast application potential.

Dual-Functional Ln-OFs for Efficient Luminescence Sensing and Photoreduction of Cr(VI) without Additional Photosensitizers and Cocatalysts

Six isostructural stable lanthanide metal–organic Frameworks (Ln-OFs), namely, [Ln(ADBA)(HCOO)(DMF)] (Ln = Sm(1), Tb(2), Dy(3), Ho(4), Er(5), Eu(6), H2ADBA = 4,4′-(anthracene-9,10-diyl)dibenzoate, DMF = N,N-dimethylformamide), have been successfully obtained by the solvothermal method based on an aromatic carboxylic acid ligand H2ADBA. 1–6 have a similar three dimensional (3D) network structure with pts topology based on dinuclear metallic clusters {Ln2}. 1–6 all have excellent chemical and thermal stabilities, which is beneficial to carrying out fluorescence sensing and achieving catalytic reactions. 1–6 show admirable fluorescent properties in aqueous solution and can quickly and efficiently detect Fe3+, Cr2O72–, and nitrofurazone (NZF) with high selectivity and excellent sensitivity. Remarkably, upon completion of detection, the Cr2O72– ion in wastewater can be reduced into Cr3+ by photocatalyst 1, which is ascribed to its broad-range visible-light absorption and recyclable stability. During the reduction process, ethanol is an optimal hole scavenger; 1 shows an excellent convert efficiency (99%), a high rate constant (k) of 0.066 min–1, and a high Cr(VI) reduction rate of 0.158 mgCr(VI)·g–1cata·min–1 at pH = 2. Furthermore, photocatalyst 1 can be reused for three cycles without significant loss of catalytic activity. Until now, it is the first example to report that the photocatalytic reduction of Cr(VI) is achieved only by using 3D rare earth MOFs without additional photosensitizers and cocatalysts. The reasonable mechanisms of luminescence sensing and photocatalytic reaction were also investigated systematically via indispensable testing technologies and theoretical simulated calculation.

Rapid and accurate sensing platform based on lanthanide metal-organic framework and aptamer for Vibrio parahaemolyticus diagnosis

In this study, a rapid visual analysis strategy for pathogens was constructed based on lanthanide metal–organic frameworks (LnMOFs) and FAM-aptamer. The dual fluorescence signal changes were realized by the competitive binding effect of the target and LnMOFs on the FAM-aptamer. The nitrocellulose membrane (NC membrane) is used as the signal output platform, and the G/R value in Red, Green, Blue (RGB) of negative and positive signals is collected to output the detection results. Using Vibrio parahaemolyticus in seafood as model target, the detection performance of dual fluorescence sensing strategy was verified. Under the optimal conditions, the G/R difference between the positive and negative signals and the concentration of Vibrio parahaemolyticus was linear in the range of 102-105 colony forming units (CFU)/mL, and the detection limit was 102 CFU/mL. The method is simple to operate and the detection time can be controlled within 20 min. It can be developed as a portable detection kit, providing a new technical means for the safety and quality control of food supply chain.

Stable Lanthanide–Organic Frameworks: Crystal Structure, Photoluminescence, and Chemical Sensing of Vanillylmandelic Acid as a Biomarker of Pheochromocytoma

Several isostructural lanthanide metal-organic frameworks, viz. [Ln(DCHB)1.5phen]n (Ln-MOFs, where Ln = Eu for 1, Tb for 2, Sm for 3 and Dy for 4), are successfully synthesized through the hydrothermal reactions of 4'-di(4-carboxylphenoxy)hydroxyl-2, 2'-bipyridyl (H2DCHB) and lanthanide nitrates as well as chelator 1,10-phenantroline (phen). These structures are characterized by single-crystal X-ray diffraction, and the representative Ln-MOF 1 is a fivefold interpenetrated framework with the uncoordinated Lewis base N sites form DCHB2- ligands. The photoluminescence research studies reveal that Ln-MOFs 1-4 exhibit characteristic fluorescent emissions from ligand-induced lanthanide Ln(III) ions, while the single-component emission spectra of Ln-MOF 4 are all located in a white region under different excitations. The absence of coordinated water and the interpenetration property of the structures are conducive to the structure rigidity, and the results display that Ln-MOF 1 has high thermal/chemical stabilities in common solvents and a wide pH range as well as the boiling water. Notably, luminescent sensing studies reveal that Ln-MOF 1 with prominent fluorescence properties can perform in highly sensitive and selective sensing of vanillylmandelic acid (VMA) in aqueous systems (KSV = 562.8 L·mol-1; LOD = 4.6 × 10-4 M), which can potentially establish a detection platform for the diagnosis of pheochromocytoma via multiquenching mechanisms. Moreover, the 1@MMMs sensing membranes comprised of Ln-MOF 1 and a poly(vinylidene fluoride) (PVDF) polymer can also be facilely developed for VMA detection in aqueous media, suggesting the enhanced convenience and efficiency of practical sensing applications.

Facile preparation of codoped lanthanide metal–organic frameworks with efficient energy transfer for ratiometric temperature sensing

Facile preparation of codoped lanthanide metal–organic frameworks with efficient energy transfer for ratiometric temperature sensing

Visual ratiometric fluorescence sensing of L-lactate in sweat by Eu-MOF and the design of logic devices

Using 1, 4-H2NDC as ligand and Eu as the center metal, the lanthanide MOF Eu-NDC was synthesized by hydrothermal method. The material showed a fast ratiometric response to L-lactate, and the fluorescence of the material varied from red to blue with the growth of lactate concentration, which can be used as a fluorescent sensor for L-lactate in sweat. The sensor exhibited good fluorescence stability to interfering components in human sweat and good detection limits for lactate in artificial sweat. Based on this, a visualized molecular logic gate that can monitor sweat lactate levels was constructed, and the material's characteristic of showing different colors with lactate concentration changes was used to indicate possible hypoxia during exercise, opening a new path for combining sweat lactate monitoring with smart molecular devices.

Facile synthesis of 2D Europium-metal organic frameworks nanosheets for highly efficient electrochemiluminescence in DNA detection

Lanthanide metal organic frameworks (Ln-MOFs) with self-luminous behavior are considered promising emitters of electrochemiluminescence (ECL) due to their unique antenna effects. In this study, the novel 2D Europium-metal organic frameworks (Eu-MOFs) nanosheets were synthesized by simply blending 1, 10-phenanthroline-2, 9-dicarboxylic acid (PDA) and Eu salts at room temperature. When N, N-diethylethylenediamine (DEAEA) was used as the efficient co-reactant, the 2D Eu-MOFs exhibited stronger and steadier ECL performance compared with 2D Europium-metal organic gels (Eu-MOGs) synthesized using similar steps, due to their rigid skeletons and higher crystalline degree, which facilitated electron transfer. In addition, we designed a switching mode ECL biosensor, which was combined with an exonuclease-assisted DNA walker cycling signal amplification strategy, enabled the ultra-sensitive detection of the I27L gene, which was significantly associated with an increased risk of maturity-onset diabetes of the young (MODY). When the target DNA was present, DNA walker recycle amplification occurred driven by exonuclease III (Exo III). Subsequently, the ECL intensity of the system was reduced by introducing the ferrocene-labeled probe (H2-Fc) as a signal quencher. Under the optimal experimental conditions, a wide detection linear range of the target DNA was observed from 1 fM to 10 nM with a low detection limit of 447 aM. This research provided new possibilities for a gentle and simple method to obtain 2D MOFs with stable ECL signals for the sensitive detection of specific DNA sequences.

Efficient Eu3+-Integrated UiO-66 Probe for Ratiometric Fluorescence Sensing of Styrene and Cyclohexanone

The development of probes with sensitive and prompt detection of volatile organic compounds (VOCs) is of great importance for protecting human health and public security. Herein, we successfully prepared a series of bimetallic lanthanide metal-organic framework (Eu/Zr-UiO-66) by incorporating Eu3+ for fluorescence sensing of VOCs (especially styrene and cyclohexanone) using a one-pot method. Based on the multiple fluorescence signal responses of Eu/Zr-UiO-66 toward styrene and cyclohexanone, a ratiometric fluorescence probe using (I617/I320) and (I617/I330) as output signals was developed to recognize styrene and cyclohexanone, respectively. Benefitting from the multiple fluorescence response, the limits of detection (LODs) of Eu/Zr-UiO-66 (1:9) for styrene and cyclohexanone were 1.5 and 2.5 ppm, respectively. These are among the lowest reported levels for MOF-based sensors, and this is the first known material for fluorescence sensing of cyclohexanone. Fluorescence quenching by styrene was mainly owing to the large electronegativity of styrene and fluorescence resonance energy transfer (FRET). However, FRET was accounted for fluorescence quenching by cyclohexanone. Moreover, Eu/Zr-UiO-66 (1:9) exhibited good anti-interference ability and recycling performance for styrene and cyclohexanone. More importantly, the visual recognition of styrene and EB vapor can be directly realized with the naked eyes using Eu/Zr-UiO-66 (1:9) test strips. This strategy provides a sensitive, selective, and reliable method for the visual sensing of styrene and cyclohexanone.

Ratiometric Luminescent Thermometer Based on the Lanthanide Metal–Organic Frameworks by Thermal Curing

The high-performance optical thermometer probes are of great significance in diverse areas; lanthanide metal-organic frameworks (Ln-MOFs) are a promising candidate for luminescence temperature sensing owing to their unique luminescence properties. However, Ln-MOFs have poor maneuverability and stability in complex environments due to the crystallization properties, which then hinder their application scope. In this work, the Tb-MOFs@TGIC composite was successfully prepared using simple covalent crosslinking through uncoordinated -NH2 or COOH on Tb-MOFs reacting with the epoxy groups on TGIC {Tb-MOFs = [Tb2(atpt)3(phen)2(H2O)]n; H2atpt = 2-aminoterephthalic acid; phen = 1,10-phenanthroline monohydrate}. After curing, the fluorescence properties, quantum yield, lifetime, and thermal stability of Tb-MOFs@TGIC were remarkably enhanced. Meanwhile, the obtained Tb-MOFs@TGIC composites exhibit excellent temperature sensing properties in the low-temperature (Sr = 6.17% K-1 at 237 K), physiological temperature (Sr = 4.86% K-1 at 323 K), or high-temperature range (Sr = 3.88% K-1 at 393 K) with high sensitivity. In the temperature sensing process, the sensing mode of single emission changed into double emission for ratiometric thermometry owing to the back energy transfer (BenT) from Tb-MOFs to TGIC linkers, and the BenT process enhanced with the increase of temperature, which further improved the accuracy and sensitivity of temperature sensing. Most notably, the temperature-sensing Tb-MOFs@TGIC can be easily coated on the surface of polyimide (PI), glass plate, silicon pellet (SI), and poly(tetrafluoroethylene) plate (PTFE) substrates by a simple spraying method, which also exhibited an excellent sensing property, making it applicable for a wider T range measurement. This is the first example of a postsynthetic Ln-MOF hybrid thermometer operative over a wide temperature range including the physiological and high temperature based on back energy transfer.

Influence of solvent coordination on crystal structure and luminescent property in lanthanide MOFs

Two isomorphous Ln-MOFs with pyridine-2, 4, 6-tricarboxylic acid (H3PTC), Eu-PTC-DMF and Tb-PTC-DMF, were prepared by solvothermal synthesis method and characterized by IR spectroscopy, and thermogravimetric analysis, and powder X-ray diffraction techniques. Single-crystal structural analyses indicate that the Ln1 and Ln2 coordination polyhedra are connected by sharing corners of polyhedra to construct 1D chain, which further form a 3D coordination framework through the connection of PTC3- ligands, and the solvent molecules of DMF and H2O, as the terminal ligands, are bound to polyhedra of Ln3+ ions. Investigation of the photophysical property at ambient conditions revealed that both Ln-MOFs emit characteristic luminescence of Ln3+ ions. Eu-PTC-DMF and Tb-PTC-DMF possess microsecond scale emission lifetime with absolute quantum yields as high as 33.1% and 50.8%, respectively.

Series of Dual Functional Two-Dimensional RE-OFs for Nitrophenol Reduction and Dye Separation.

The rational design and preparation of stable and multifunctional metal-organic frameworks (MOFs) with excellent catalysis and adsorption properties are desirable but are great challenges. The nitrophenol (NP) reduction to aminophenols (APs) by using the catalyst Pd@MOFs is an effective strategy, which has attracted extensive attention in recent years. Here, we report four stable isostructural two-dimensional (2D) rare earth metal-organic frameworks [RE4(AAPA)6(DMA)2 (H2O)4][DMA]3[H2O]8 (namely LCUH-101, RE = Eu, Gd, Tb, Y; AAPA2- = 5-[(anthracen-9-yl-methyl)-amino]-1,3-isophthalate), which feature a 2D layer structure with sql topology of point symbol {44·62} and exhibit excellent chemical stability and thermostability. The as-synthesized Pd@LCUH-101 was utilized for the catalytic reduction of 2/3/4-nitrophenol, which indicates high catalytic activity and recyclability attributed to the synergistic effect between Pd nanoparticles and the 2D layered structure. Of note, the turnover frequency (TOF), the reaction rate constant (k), and the activation energy (Ea) of Pd@LCUH-101 (Eu) in the reduction of 4-NP, respectively, are 1.09 s-1, 2.17 min-1, and 50.2 kJ·mol-1, which show that it has superior catalytic activity. Remarkably, LCUH-101 (Eu, Gd, Tb, and Y) are multifunctional MOFs that can effectively absorb and separate mixed dyes. The appropriate interlayer spacing enables them to efficiently adsorb methylene blue (MB) and rhodamine B (RhB) in aqueous solution, with adsorption capacities of 0.97 and 0.41 g·g-1, respectively, which is one of the highest values among those of the reported MOF-based adsorbers. Meanwhile, LCUH-101 (Eu) can be used for the separation of the dye mixture MB/MO and RhB/MO, and the excellent reusability enables LCUH-101 (Eu) to be used as chromatographic column filters to quickly separate and recover dyes. Therefore, this work provides a new strategy for the exploitation of stable and efficient catalysts for NP reduction and adsorbents for dyes.

Achieving Enhanced Photochromism of Spiropyran in Pretreated Nanoporous Lanthanide Metal–Organic Frameworks for Information Storage Applications

Spiropyran and its derivatives are an important class of photochromic molecules that have a wide range of applications in information storage and anti-counterfeiting. However, the easy tight accumulation of molecules under the solid state of spiropyran affects its discoloration efficiency, which is still a challenge to improve the solid photochromic properties. In this paper, a method of loading spiropyran by pretreatment of a lanthanide metal–organic framework (MOF) to improve its photo-response ability is reported. The lanthanide MOF is pretreated by methanol activation and 330 °C calcination to remove the unwanted ligands and some unreacted impurities in the framework. Compared to the pore size of the untreated framework (2.06 nm), the pore sizes of the framework activated by methanol (2.5 nm) and sintering at 330 °C (4.23 nm) were increased. Then, the spiropyran was loaded into a lanthanide MOF by solvent adsorption. After pretreatment of the Tb-MOF, the loading content of spiropyran increased from the initial 4.3 to 9.08 and 12.13%. After 365 nm UV illumination, the difference value in UV absorbance of framework pretreated composites gradually increased from 0.24 to 0.36, accompanied by color transition from yellow to violet. Due to the fluorescence resonance energy transfer effect between the donor lanthanide ion and the acceptor spiropyran, the fluorescence emission transition of the composite material was realized within 10 min. Among them, the fluorescence emission of the untreated composite of the frame can only change from pale yellow to orange, and the maximum fluorescence intensity is 4.4 × 105 CPS, while the fluorescence emission can change from yellow to red after frameworks’ pretreatment, and the fluorescence intensity is significantly improved, which is 6.4 × 105 and 7.5 × 105 CPS, respectively. By applying a composite material to a filter paper, a pattern with high contrast can be made. The pattern can be irradiated with ultraviolet light to realize the physical and fluorescence changes and can be restored to the initial state after being irradiated with green light with a wavelength of 530 nm for 10 min. This not only improves the solid photochromic properties of spiropyran but also provides the application possibility for information storage.

Impact of Ligands on the Properties of Lanthanide Metal‐Organic Frameworks

AbstractA series of lanthanide metal‐organic frameworks (MOFs) have been assembled with a series of functionalized [1,1′:4′,1′′‐terphenyl]‐4,4′′‐dicarboxylic acid ligands. The relationship between the ligand properties and the corresponding MOF properties has been studied. The structures of the MOFs depend on the solvent‐ligand and ligand‐ligand interactions, as well as the size of the non‐coordinating functional groups of the ligands. The differences in thermal stability among the ligands are inherited and amplified by corresponding lanthanide MOFs. The ligands bearing methyl, ether, and aldehyde functional groups are capable of sensitizing the emission from the lanthanide centers, whereas the ligand with α,β‐unsaturated ketone functional groups are non‐emissive due to the mismatch of the ligand and metal energy levels.

Fabrication of the Antibiotic Sensor by the Multifunctional Stable Adjustable Luminescent Lanthanide Metal–Organic Frameworks

In recent years, the irrational use of antibiotics has become very widespread. It is necessary to regulate this phenomenon through antibiotic detection. In this work, a series of isomorphic Ln-MOFs (Ln = Tb3+ and Eu3+) were synthesized from 1,3,5-tri(4-carboxyphenyl)benzene (H3L) and Ln3+ by the solvothermal method for the first time. A series of 1-EuxTb1-x with different luminescence were doped by changing the molar ratio of Tb3+ and Eu3+. Ln3+ forms a 4-connected 2D network structure through self-assembly with fully deprotonated L3-. It shows good chemical stability in water, and its luminescence is not affected by aqueous solutions with different pH values. 1-Eu demonstrates rapid and sensitive detection capabilities for MDZ and TET with good recyclability and low detection limits (10-5). In order to increase the practicability of 1-Eu, two portable sensors have been prepared, in which the fluorescent film (Film@1-Eu) has a detection limit of 10-4, and the sensitivity is only less than 10% of the titration results. A portable fluorescent test paper can reach the detection limit of 14.7 ppm. This study provides a new idea for the application of stable multifunctional materials in the field of fluorescence sensing.

Boosting the optical properties of polylactic acid/ lanthanide-based metal-organic framework composites

Luminescent lanthanide metal-organic frameworks (LnMOF) are gathering much interest in the scientific community due to their exceptional optical properties, which have the potential to revolutionize several application fields, including anti-counterfeiting. The traceability of the original products is an ever-growing demand for producers and end-users to verify the authenticity of produced goods. Following this newfound need, we propose an anti-counterfeiting method based on a quick-response (QR) code, with a very specific verification procedure, using a luminescent LnMOF-based composite. The embedded code will only react to certain stimulation, hence it can only be unlocked using the sequence that is programmed to respond to. For that purpose, we explored the incorporation of fresh LnMOFs, with europium (EuMOF) and terbium (TbMOF), on a biodegradable polymer matrix of polylactic acid (PLA). A homogeneous mixture of PLA/LnMOF was produced via a two-step process including solvent casting followed by thermal mixing, after achieving the optimized concentration for each filler. The optical characterization of the fresh composites showed an excellent response to selective excitation, with well-defined intraionic lines for TbMOF @ 542 nm (5D4→7F5) and for EuMOF @ 615 nm (5D0→7F2). PLA/Eu, TbMOF composites were also explored to create an additional level of encryption by tuning the emitted color with the appropriate excitation stimuli. Hence, these new luminescent composite materials can be used as traceable optical tags for a wide variety of polymeric products, capable to respond to a very specific excitation wavelength and act as a level three luminescent security marker, whose decoding demands the assessment of more than one factor, with near-impossible replication. Additionally, this technology has a high potential for scalability since the applied processing techniques used for the production of the optically active QR code are commonly employed in the polymer industry. Nevertheless, the analysis of the aged effects clearly indicates the need for a definition of new strategies to enhance the efficiency of the sensitization process of the Ln3+ intraionic emission.