Series Of Lanthanide Metal-organic Frameworks Research Articles

Heterogeneous Acetalization of Benzaldehyde over Lanthanide Oxalate Metal-Organic Frameworks.

Lanthanides (Ln) from the f-blocks of the periodic table have gained significant interest due to their unique characteristics, including magnetism, photoluminescence, and catalysis. In this study, a series of lanthanide metal-organic frameworks [Ln-MOFs, Ln = Eu(III), Tb(III), Nd(III), Er(III), Ho(III), Gd(III), Pr(III), and Dy(III)] were constructed based on oxalic acid and lanthanide metals as the building blocks. These MOFs were comprehensively characterized using various analytical and spectroscopic techniques, including powder X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, nitrogen adsorption-desorption, and Raman spectroscopy. The magnetic properties of the investigated materials were examined, revealing both antiferromagnetic and ferromagnetic interactions within the Ln-Ox MOFs. The catalytic activities of Ln-Ox MOFs were evaluated through the heterogeneous acetalization of benzaldehyde with methanol. Reaction yields by the reported catalysts varied up to 90% depending on the MOF's metal center, and the product was confirmed by gas chromatography-mass spectrometry. Recycling experiments have confirmed the stable regeneration of Ln-Ox MOFs in which the product yields remained the same over four consecutive cycles. The hydrothermal synthesis of these MOFs paves the way for a diverse array of materials showcasing unique lanthanide properties, making them suitable for various applications.

Lanthanide metal-organic frameworks as ratiometric fluorescent probes for real-time monitoring of PFOA photocatalytic degradation process

The assessment of perfluorooctanoic acid (PFOA) photocatalytic degradation usually involves tedious pre-treatment and sophisticated instrumentation, making it impractical to evaluate the degradation process in real-time. Herein, we synthesized a series of lanthanide metal-organic frameworks (Ln-MOFs) with outstanding fluorescent sensing properties and applied them as luminescent probes in the photocatalytic degradation reaction of PFOA for real-time evaluation. As the catalytic reaction proceeds, the fluorescence color changes significantly from green to orange-red due to the different interaction mechanisms between the electron-deficient PFOA and smaller radius F− with the ratiometric fluorescent probe MOF-76 (Tb: Eu = 29:1). The limit of detection (LOD) was calculated to be 0.0127 mM for PFOA and 0.00746 mM for F−. In addition, the conversion rate of the catalytic reaction can be read directly based on the chromaticity value by establishing a three-dimensional relationship graph of G/R value-conversion rate-time (G/R indicates the ratio between green and red luminance values in the image.), allowing for real-time and rapid tracking of the PFOA degradation. The recoveries of PFOA and F− in the actual water samples were 99.3–102.7% (RSD = 2.2–4.4%) and 100.7–105.3% (RSD = 3.9–6.8%), respectively. Both theoretical calculations and experiments reveal that the detection mechanism was attributed to the photoinduced electron transfer and energy transfer between the analytes and the probe. This method simplifies the sample analysis process and avoids the use of bulky instruments, and thus has great potential on the design and development of quantitative time-resolved visualization methods to assess catalytic performance and reveal mechanisms.

Energy transfer, anticounterfeiting, white light emission and sensing in fine-regulating series of lanthanide metal-organic frameworks

Three lanthanide ions and a rigid (1,1'-biphenyl)-2,4,6-tricarboxylic acid (H3bptc) ligand led to the isostructural lanthanide metal-organic frameworks (Ln-MOFs) {[Ln(bptc) (H2O)3]·3H2O}n (Lnbptc, Ln = Eu, Tb, Gd, EuxTb1–x, EuxGd1–x, TbxGd1–x, and Eu0.12Tb0.52Gd0.36). The density functional theory (DFT) and time-dependent DFT calculation were expanded on H3bptc, which point to the occurrence of “antenna effect”. The minor diameter samples of Eubptc, Tbbptc, and Gdbptc can also be attained via the microwave synthesis and employed for handwriting anticounterfeiting. Interestingly, the typical red emission of Eu3+ and green emission of Tb3+ could be fine-tuned by Gd3+ via chemical mixing to be full-color emissions bimetallic doped EuxTb1–xbptc, EuxGd1–xbptc, and TbxGd1–xbptc. The above synthetic bimetallic MOFs can be fixed in positioning boxes of quick response (QR) codes with diverse emission for anticounterfeiting. The message can be decoded under the irradiation of 365 nm ultraviolet lamp while invisible in the daylight. Notably, the trimetallic doped Eu0.12Tb0.52Gd0.36bptc emits white light with the CIE color coordinate (0.34, 0.34). Furthermore, Tbbptc is demonstrated to be a sensitive probe toward nitrobenzene and acetone with multiple mechanisms.

Series of Luminescent Lanthanide MOFs with Regular SHG Performance.

Second-harmonic generation (SHG) is a kind of nonlinear optical phenomenon which has been widely used in optical devices, and factors influencing its signal are very complex. Here, taking advantage of excellent structural designability and overcoming the limitations of various coordinations of lanthanide metals, for the first time a series of lanthanide metal-organic frameworks (Ln-MOFs) with one particular ligand were synthesized and structurally characterized to study the interference of the SHG signal. The optical performance including single-photon fluorescence and SHG was collected and analyzed. It is found that all 13 kinds of Ln-MOFs can be divided into 2 crystal configurations by their individual space groups and Ln-MOFs with coordinated metal atoms from La to Tb possessing the noncentrosymmetric C2 space group exhibit the SHG property, the intensity of which depends on the type of metal atoms, the pumping wavelength, and the size of the single-crystal particles. This is the first time that the relationship between the nonlinear optical properties and the structure, metal atoms, pumping wavelength, crystal size of the whole series of Ln-MOFs is studied systematically, providing a lot of interesting results and enriching the research scope of nonlinear optics and materials science.

Lanthanide Metal-Organic Frameworks as Luminescent Sensor for Toluene

Two new series of lanthanide metal-organic frameworks (LnMOFs) are successfully obtained via a solvothermal reaction, based on the corresponding lanthanide(III) nitrates and the ligand of methylmalonic acid (MMA). Where 1a–1c are synthesized by Ln(NO3)3 (Ln3+ = Eu, 1a; Gd, 1b; Tb, 1c) and MMA, 2a and 2b are obtained with Ln(NO3)3 (Ln3+ = Eu, 2a; Tb, 2b), MAA, and in the presence of capping agent 1,10-phenanthroline (phen). The five new compounds were structurally determined by single-crystal X-ray diffraction, FT-IR, PXRD, TGA and luminescence. Furthermore, the sensing property reveals that 1a is a luminescent sensor for toxic solvent of toluene.

Tunable Light Emission and Multiresponsive Luminescent Sensitivities in Aqueous Solutions of Two Series of Lanthanide Metal-Organic Frameworks Based on Structurally Related Ligands.

Two series of lanthanide metal-organic frameworks (Ln-MOFs) from two structurally related flexible carboxylate-based ligands were solvothermally synthesized. H3L2 with additional -CH2-groupprovides more flexibility and different coordination modes and conformations compared with H3L1. As a result, 2-Ln MOFs are modulated from two-dimensional kgd of 1-Ln to three-dimensional rtl topological frameworks and further achieve enhanced chemical stability. The Eu- and Tb-MOFs exhibit strong fluorescent emission at the solid state because of the antenna effect of the ligands. Interestingly, the emissions can be tuned by simply doping Eu3+ and Tb3+ of different concentrations within the Eu xTb1- x MOFs. Notably, 2-Ln MOFs realize nearly white light emission by means of a trichromatic approach (red of Eu(III), green of Tb(III), and blue of the H3L2 ligand). Furthermore, 2-Ln MOFs also exhibit water stability and demonstrate high selective and sensitive sensing activities toward Fe(III) and Cr(VI) in aqueous solutions. The results further highlight the importance of the ligand flexibility on tuning MOF structures with improved structural stability and ion-sensing properties.

Luminescence properties of a family of lanthanide metal-organic frameworks

Abstract Two isostructural series of lanthanide metal-organic frameworks denoted as SUMOF-7II (Ln) and SUMOF-7IIB (Ln) (Ln = La, Ce, Pr, Nd, Sm, Eu, and Gd) were synthesized using4,4′,4''-(pyridine-2,4,6-triyl)tris(benzoic acid) (H3L2) and a mixture of H3L2 and 4,4′,4′′-(benzene-1,3,5-triyl)tris(benzoic acid) (H3BTB) as linkers, respectively. Both series were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermal analysis (TGA), and photoluminescence spectroscopy. Photoluminescence measurements show that Eu-MOFs demonstrate a red emission while Pr- and Nd-MOFs display an emission in the near-infrared (NIR) range. On the other hand, La-, Ce-, Sm- and Gd-MOFs exhibit only a ligand-centered emission. The average luminescence lifetimes in the SUMOF-7IIB series are 1.3–1.4-fold longer than the corresponding ones in the SUMOF-7II series. SUMOF-7IIs show a good photo- and thermal stability. Altogether, the properties of SUMOF-7II and SUMOF-7IIB render them promising materials for applications including sensing, biosensing, and telecommunications.

A Series of Lanthanide Metal-Organic Frameworks with Interesting Adjustable Photoluminescence Constructed by Helical Chains.

Based on the isonicotinic acid (HIN=pyridine-4-carboxylic acid), seven lanthanide metal-organic frameworks (MOFs) with the formula [Ln(IN)2 L] (Ln=Eu (1), Tb (2), Er (3), Dy (4), Ho (5), Gd (6), La (7), L=OCH2 CH2 OH) have been synthesized by mixing Ln2 O3 with HIN under solvothermal conditions, and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, infrared spectroscopy, and fluorescence spectroscopy. Crystal structural analysis shows that compounds 1-6 are isostructural, crystallize in a chiral space group P21 21 21 , whereas compound 7 crystallizes in space group C2/c. Nevertheless, they all consist of new intertwined chains. Simultaneously, on the basis of the above-mentioned compounds, we have realized a rational design strategy to form the doped Ln MOFs [(Eux Tb1-x )(IN)2 L] (x=0.35 (8), x=0.19 (9), x=0.06 (10)) by utilizing Tb(III) as the second "rare-earth metal". Interestingly, the photoluminescence of [(Eux Tb1-x )(IN)2 L] are not only adjustable by the ratios of Eu/Tb, but also temperature or excitation wavelength.