Ln MOFs Research Articles

Epitaxial Growth of Multicolor Lanthanide MOFs by Ultrasound for Photonic Barcodes.

Epitaxially grown lanthanide metal-organic frameworks (Ln MOFs) exhibit multicolor and characteristic Ln emission with sharp emission bands, which are of great value in the field of information security and anti-counterfeiting. Epitaxial growth of Ln MOFs is generally achieved by solvothermal or hydrothermal methods, which suffer from challenges such as high reaction temperature and long growth time. Here, we report the fast epitaxial growth of multicolor lanthanide MOFs by an ultrasonic method at room temperature. The TbSmSQ shows a core-shell type structure with the Tb ion in the core and Sm in the shell within one crystal and exhibits the characteristic emission lines of Tb and Sm, respectively. The nonporous structure and large distance between lanthanide ions effectively avoid the influence of solvent vapor on the intensity and color of luminescence emission. Its application as photonic barcodes has been studied. This work demonstrates the feasibility of epitaxial growth of multicolor Ln MOFs by the ultrasonic method and its value for anti-counterfeiting and information security applications.

Synthesis and Characterizations of Novel bi-ligand TbEu(cpioa)phen Phosphors with High Quantum Efficiency for WLED Applications.

The hydrothermal method was employed to synthesize a novel bi-ligands LnMOF: Ln(cpioa)phen. The secondary ligand 1, 10-phen serves as a bridging agent to further facilitate energy transfer between Ln ions and the primary ligand H3cpioa. A comparison between Ln(cpioa) MOFs (Ln: Tb3+, Eu3+) and Ln(cpioa)phen MOFs (Ln: Tb3+, Eu3+) reveals that addition of the secondary ligand significantly improves the emission intensity by as high as almost 34 times. After detailed structural study, it is found that different Ln ions have the similar coordination in the Ln(cpioa)phen MOF. In addition, the chromaticity of Ln(cpioa)phen MOFs can be easily tuned by the amounts of doping Ln ions. La0.974Tb0.0255Eu0.0005(cpioa)phen MOF has a white emission with a CIE coordinate of (0.323, 0.343). Characterizations of corresponding LED devices show that device based on Ln(cpioa)phen MOF has better photoluminescence performances, which indicates that Ln(cpioa)phen MOF has great potential of for WLED applications.

High-Entropy Lanthanide-Organic Framework as an Efficient Heterogeneous Catalyst for Cycloaddition of CO2 with Epoxides and Knoevenagel Condensation.

Multimetallic synergistic effects have the potential to improve CO2 cycloesterification and Knoevenagel reaction processes, outperforming monometallic MOFs. The results demonstrate superior performance in these processes. To investigate this, we created and characterized a selection of single-component Ln(III)-MOFs (Ln=Eu, Tb, Gd, Dy, Ho) and high-entropy lanthanide-organic framework (HE-LnMOF) using solvent-thermal conditions. The experiments revealed that HE-LnMOF exhibited heightened catalytic efficiency in CO2 cycloesterification and Knoevenagel reactions compared to single-component Ln(III) MOFs. Moreover, the HE-LnMOF displayed significant stability, maintaining their structural integrity after five cycles while sustaining elevated conversion and selectivity rates. The feasible mechanisms of catalytic reactions were also discussed. HE-LnMOF possess multiple unsaturated metal centers, acting as Lewis acid sites, with oxygen atoms connecting the metal, and hydroxyl groups on the ligand serving as base sites. This study introduces a novel method for synthesizing HE-LnMOF and presents a fresh application of HE-LnMOF for converting CO2.

Benzotrithiophene-based MOFs: interchromophoric interactions affected Ln(III) crystallization selectivity and optoelectronic properties.

Metal-organic frameworks (MOFs) provide an ideal platform for the assembly of chromophores and thus show wide potential applications in optoelectronic devices. The spatial arrangement and interaction of the incorporated chromophores play a key role in the generation of coherent optical and electronic properties. In this work, two series of benzo-(1,2;3,4;5,6)-tristhiophene (BTT) based Ln-MOFs (Ln-1s and Ln-2s) were synthesized. These two series of MOFs present different assembly states of BTT chromophores, that is, BTT-containing ligands exist as separated monomers in Ln-1s but gather as dimers in Ln-2s. From the comparison between these two series of MOFs and theoretical calculations, we show for the first time that this chromophore assembly state difference could affect the crystallization selectivity of MOFs towards different Ln3+ ions. In addition, the interaction between BTT chromophores in the dimer also leads to the red-shifted photoluminescence and enhanced photocurrent of Ln-2s relative to those of Ln-1s. The results of this work demonstrate the multiple functions of interchromophoric interactions in the structures and optoelectronic properties of MOFs.

New 2D Lanthanide MOFs Constructed from Bis(imide) Pyromellitic Alanine Ligands with Enhanced Fluorescence toward Activation and Modulation of Microstructure

Five isostructural 2D lanthanide (Ln) MOFs were synthesized using 2,2′-(1,3,5,7-tetraoxo-5,7-dihydropyrrolo[3,4-f]isoindole-2,6(1H,3H)-diyl)dipropionic acid (PBIA ligand) semiflexible ligand and Pr/Eu/Tb/Er/Tm hydrated nitrates in DMF leading to PBIA–Pr/PBIA–Eu/PBIA–Tb/PBIA–Er/PBIA–Tm materials. New MOFs were characterized employing Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), single crystal and powder X-ray diffractions (SCXRD/PXRD), photoluminescence, and scanning electron microscopy (SEM). MOFs crystallized in P1̅ triclinic space group, developing 2D structures through different ligand coordination-conformation schemes toward dinuclear Ln–metal clusters (SBU). Materials were thermally stable ca. 400 °C, being activated partially removing DMF → Ln molecules giving PBIA–PrACT/PBIA–EuACT/PBIA–TbACT/PBIA–ErACT/PBIA–TmACT phases reorganizing the PBIA ligand toward isobidentate mode, releasing ca. two of six-coordinated DMF per SBU. Just Eu/Tb materials could be studied in the 200–800 nm range showing characteristic emission bands, and the PBIA ligand was not sensitization-suitable for other Ln emissions. Band shape modification and emission intensity enhancement of 6.7(Eu) and 30.6(Tb) resulted in Eu/Tb-activated compounds. Excitation of PBIA–Eu/PBIA–EuACT directly in Eu3+ resulted efficient, but not via the PBIA ligand. In PBIA–Tb/PBIA–TbACT compounds, PBIA ligand excitation is more efficient and PBIA–TbACT could be directly excited in Tb3+. Hence nonradiative processes are playing decisive roles in luminescent properties. Isostructural materials resulted, but different Ln-metals provided different morphologies/sizes, modulating microstructures, and luminescence properties. These materials would be candidates for molecular/ionic sensing, through emission modulation, mainly when Eu and Tb are employed as Ln.

Interpenetrated Metal-Organic Frameworks with ftw Topology and Versatile Functions.

Through an "isoreticular expansion" strategy, a large number of highly porous zirconium-based metal-organic frameworks (Zr-MOFs) have been achieved using extended organic linkers in the past few years. However, interpenetrated Zr-MOFs with ftw topology have scarcely been reported, mainly owing to the used bulky tetratopic linkers that effectively prevent the network interpenetration. Here, we report a new family of zirconium and lanthanide (Ln) MOFs with ftw topology, constructed by hexanuclear Zr or Ln (Ln = Eu, Tb, Gd, Dy, Tm, Yb, Nd, and Er) clusters and a spirobifluorene-center tetracarboxylate linker. Our studies reveal that the isostructural Zr and Ln MOFs are all doubly interpenetrated with ultrahigh thermal and chemical stability. The observed unusual interpenetration can be attributed to the specific geometry of the spirobifluorene-center tetratopic linker. Gas adsorption studies show that the interpenetrated Zr-MOF is still highly porous and exhibits high performance for CO2 storage, which can be attributed to the strong CO2 binding environment contributed by the reduced pore size. In addition, the presented MOFs display strong characteristic luminescence in the UV-vis-NIR region. Moreover, the incorporation of the spiro-center linker into the framework can efficiently produce two-photon-excited photoluminescence with a large action cross-section value, which also benefited from the high packing density of the nonlinear optical chromophore linker in the interpenetrated structure.

Luminescence Sensing of Fe3+ and Nitrobenzene by Three Isostructural Ln–MOFs Assembled by a Phenyl‐Dicarboxylate Ligand

AbstractThree new 3D isostructural lanthanide MOFs, {[Ln(L)1.5(H2O)2]⋅2H2O⋅2DMF}n (Ln=Gd, Dy and Eu, H2L=4‐(2‐carboxyvinyl)benzoic acid)), were obtained by solvothermal reaction. The three complexes are topologically expressed as the trinodal (2,4,5)‐connected nets. The thermogravimetric analysis showed that the three complexes maintained favorable thermal stability at 425 °C. Further, the fluorescence detection tests showed that Eu‐MOF had excellent recognition ability to Fe3+ and small organic nitrobenzene in DMF and other different mixed solutions, with stable crystal skeleton revealed by PXRD date. In addition, the result of the magnetic testing showed that Dy‐MOF had antiferromagnetic properties at 1000 Oe.

Assembly of porous lanthanide metal–organic frameworks constructed by chalcone dicarboxylic acid and exploration of their properties

Using rational designed chalcone dicarboxylic acid ligand (H2L), a series of lanthanide metal–organic frameworks (Ln–MOFs) with the general formula Ln(HL)3 (Ln = La; Ce; Pr; Nd; Sm; Eu; Gd) have been obtained under the solvothermal reaction. The crystal structure analysis displays that all the Ln–MOFs are the isomorphic three-dimensional (3D) metal–organic frameworks with honeycomb cavities, in which the porosity is ∼20% that calculated via PLATON software. In addition, photocatalytic activities of Ln–MOFs for the degradation of several organic dyes have been explored, suggesting that Ln–MOFs can be used as efficient heterogeneous photocatalyst for the degradation of organic dyes.

Six Ln (III) Coordination Polymers with a Semirigid Tetracarboxylic Acid Ligand: Bifunctional Luminescence Sensing, NIR-Luminescent Emission, and Magnetic Properties

Two series of lanthanide metal organic frameworks (Ln–MOFs) [Ln(HL)(H2O)3]·H2O and [Ln(HL)(H2O)2] (Ln = Tb, 1; Er, 4; Tm, 5; Yb, 6; and Dy, 2; Ho, 3) have been successfully assembled by Ln3+ ions and asymmetric polycarboxylate ligand 3-(3′,5′-dicarboxyl-phenoxy) phthalic acid (H4L). The crystal structures, photoluminescence, and magnetic properties of these compounds have been investigated. Complexes 1, 4, 5, and 6 are isostructural and show 2D layer frameworks constructed by hydrogen bonding interactions between the coordination water molecules and the O atoms of the carboxyl group. Complexes 2 and 3 show 3D frameworks with two different interlayer channels decorated by ligands and lanthanide metals. The emission spectra show that complex 1 displays an intense green light emission and can selectively and sensitively detect for Fe3+ ion and nitromethane. In addition, near infrared (NIR) luminescence and magnetic susceptibility measurments further show that these compounds are promising functional materials.

Synthesis, structure and magnetic studies of lanthanide metal–organic frameworks (Ln–MOFs): Aqueous phase highly selective sensors for picric acid as well as the arsenic ion

A series of three lanthanide metal–organic frameworks (Ln–MOFs) consisting of a planar functionalized dicarboxylic acid was synthesized. The Ln–MOFs, with the composition [Ln3(PDC)3Cl3(H2O)]n [Ln = La (1), Nd (2) or Pr (3), PDCH2 = pyridine-2,6-dicarboxylic acid], were characterized employing spectral, time resolved fluorescence, magnetic, single crystal X-ray and PXRD analysis. X-ray crystallography confirms that the structure of the Ln–MOFs is constructed by trinuclear (Ln3) units and the deprotonated PDC2− ligand, which is simplified into a 3-c, uninodal net having the vab topology with the 10^3-point symbol. The variable temperature magnetic susceptibility data indicate that there are antiferromagnetic interactions between LnIII⋯LnIII ions in 2 and 3 with Curie constants of 5.917 (2) and 5.231 (3) cm3 K mol−1, Weiss constants −60.71 (2) and −48.43 (3) K, and zJ′ values −0.98 (2) and −0.31 (3) cm−1. The 3D polymers 1–3 are characterized as being highly selective, sensitive and discriminative dual chemosensors for picric acid (PA) and the arsenite (AsO33−) ion in aqueous medium. The sensing pathways were investigated by spectral titrations, time decay and DFT (B3LYP/def2–SVP) studies. The lowest detection limit has been discovered for the La analogue towards the sensing of both PA and AsO33− {or As(III)} ions with ∼0.22 and ∼1.46 ppb, respectively. Such MOFs exhibiting bifunctional sensing behaviour for an explosive (PA) as well as toxic ion, As(III), in the aqueous phase are disclosed as the first lanthanide 3D polymers with the lowest detection limit known so far for the said analytes.

Lanthanide metal organic frameworks based on dicarboxyl-functionalized arylhydrazone of barbituric acid: syntheses, structures, luminescence and catalytic cyanosilylation of aldehydes.

Five isostructural lanthanide MOFs, [Ln(1κOO',2κO'',3κO''',4κO''''-μ4-L)(NO3)(DMF)2]n·n(DMF) {Ln = La3+ (1), Ce3+ (2), Nd3+ (3), Sm3+ (4) and Dy3+ (5); L = 5-[2-{2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene}hydrazinyl]isophthalate; DMF = N,N'-dimethyl formamide}, based on dicarboxyl-functionalized arylhydrazone of barbituric acid were synthesized under solvothermal conditions. They were characterized by elemental analysis, FT-IR spectroscopy, thermogravimetric and X-ray diffraction analyses. Crystal structure analysis revealed that these frameworks possess a similar type of two dimensional (2D) structure with a dinuclear {Ln2(COO-)2} unit acting as a secondary building block. Topological analysis shows that these frameworks display a 3,6-connected kgd; Shubnikov plane (3.6.3.6)/dual net. They exhibit excellent heterogeneous catalytic activities (compound 2 is the most active one) towards the cyanosilylation of aldehydes under solvent-free conditions. These catalysts can be recycled at least up to five cycles without a loss of activity. Compounds 1-5 exhibit luminescence properties in the solid state at room temperature.

3D Lanthanide Metal–Organic Frameworks Based on Mono-, Tri-, and Heterometallic Tetranuclear Clusters as Highly Selective and Sensitive Luminescent Sensor for Fe3+ and Cu2+ Ions

Five novel three-dimensional lanthanide metal–organic frameworks (Ln–MOFs) constructed by 4-(3′,5′-dicarboxylphenoxy) phthalic acid (H4dcppa), namely, {[Eu(Hdcppa)(H2O)2]·H2O}n (Eu-1), [Eu1.5(dcppa) (HCOO)0.5(H2O)2]n (Eu-2), {[Ln2K2(dcppa)2(H2O)6]·mH2O}n (Ln = Eu-3, Tb-4, Gd-5, m = 5 for Eu-3 and Tb-4; m = 4 for Gd-5) (HCOOH = formic acid) have been prepared by hydro(solvo)thermal method and fully characterized. Structural analyses indicated that H4dcppa ligand took four different coordination fashions in 1–5 and, thus, resulted in diversity of the targeted Ln–MOFs: Eu-1 displays the rare 3D (5,5)-connected vbk net, containing one-dimensional left- and right-handed helical chains; Eu-2 possesses a 3D (3,8)-connected tfz-d topology constructed by trinuclear paddlewheel [Eu3(CO2)6] SBUs; 3–5 are isostructural and show 3D (Ln-dcppa4–) + 2D (K-dcppa4–) → 3D (LnK-dcppa4–) structure. Eu-3, with regular 1D channels and open Lewis basic oxygen atoms on the pore surface was utilized for specific sensing and bindin...

Luminescent Metal–Organic Framework Mixed‐Matrix Membranes from Lanthanide Metal–Organic Frameworks in Polysulfone and Matrimid

Metal–organic framework/polymer (MOF–polymer) mixed‐matrix membranes (MMMs) have been prepared by embedding the luminescent lanthanide (Ln) MOFs 3∞[Sr0.9Eu0.1Im2] and 2∞[Tb2Cl6(bipy)3]·2bipy (Im– = imidazolate, bipy = 4,4′‐bipyridine) into polysulfone (PSF, Ultrasonî S) and Matrimidî polymer films. The successful embedding of the Sr and Eu MOFs has been achieved for both matrixes, and the original MOF luminescence is maintained. The defect‐free nature of the membranes was proven by the slightly lower gas permeation of the MMMs with the dense filler particles. For the Tb–bipy MOF, successful embedding is possible for polysulfone only. For the preparation of the MOF polymer membranes, the influence of different mass fractions of the luminescent MOFs ranging from 8–16 wt.‐% and preparation from suspensions with and without ultrasonic radiation were studied. The influence of the MOF fraction is different for both membrane materials. For the polysulfone, lower amounts of MOF are preferable and lead to an increase of the overall luminescence intensity, whereas the opposite was observed for Matrimid. Altogether, the parity‐allowed emission of the Eu2+ ions is apparently stronger than the Tb3+ emission and leads to membranes with strong emission that is visible to the naked eye under normal daylight. Thereby, the Ln MOF polymer membranes open new options for the handling of luminescent MOFs.

Cover Picture: Hydrothermal Synthesis, Structure, and Optical Properties of Two Nanosized Ln26@CO3 (Ln=Dy and Tb) Cluster‐Based Lanthanide–Transition‐Metal–Organic Frameworks (Ln MOFs) (Chem. Eur. J. 8/2015)

Cover Picture: Hydrothermal Synthesis, Structure, and Optical Properties of Two Nanosized Ln₂₆@CO₃ (Ln=Dy and Tb) Cluster‐Based Lanthanide–Transition‐Metal–Organic Frameworks (Ln MOFs) (Chem. Eur. J. 8/2015)

Construction of four 3d–4f heterometallic pillar-layered frameworks containing left- and right-handed helical chains and a I−chemosensor

Four new heterometallic coordination complexes, namely, {[Zn4Ln2(imdc)4(SO4)(H2O)8]·4H2O}n [Ln = Nd (1), Sm (2), Eu (3), Gd (4); H3imdc = imidazole-4,5-dicarboxylic acid], were hydrothermally synthesized by the reactions of Ln2O3 with imidazole-4,5-dicarboxylic acid and ZnSO4·7H2O and characterized by single-crystal X-ray diffraction, infrared spectroscopy (IR), elemental analysis (EA), thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD). The single-crystal X-ray diffraction analyses reveal that these polymers are isostructural and possess an interesting 3D pillar-layered architecture with 424·64 topology, in which 2D layers constructed by alternately arranged 1D right-/left-handed helical chains of [Zn2(μ5-imdc)]n bridged via dimeric Eu2 units are pillared by μ2-SO42− and μ3-imdc3− anions. The liquid fluorescence of compounds 1–3 at room temperature shows that these complexes are very good chemosensors for I− ion, and the response of the sensor is based on fluorescence quenching of Zn–Ln MOFs by iodine ions.

Hydrothermal synthesis, structure, and optical properties of two nanosized Ln26 @CO3 (Ln=Dy and Tb) cluster-based lanthanide-transition-metal-organic frameworks (Ln MOFs).

Two Ln26 @CO3 (Ln=Dy and Tb) cluster-based lanthanide-transition-metal-organic frameworks (Ln MOFs) formulated as [Dy26 Cu3 (Nic)24 (CH3 COO)8 (CO3 )11 (OH)26 (H2 O)14 ]Cl ⋅3 H2 O (1; HNic=nicotinic acid) and [Tb26 NaAg3 (Nic)27 (CH3 COO)6 (CO3 )11 (OH)26 Cl(H2 O)15 ]⋅7.5 H2 O (2) have been successfully synthesized by hydrothermal methods and characterized by IR, thermogravimetric analysis (TGA), elemental analysis, and single X-ray diffraction. Compound 1 crystallizes in the monoclinic space group Cc with a=35.775(12) Å, b=33.346(11) Å, c=24.424(8) Å, β=93.993(5)°, V=29065(16) Å(3) , whereas 2 crystallizes in the triclinic space group P$\bar 1$ with a=20.4929(19) Å, b=24.671(2) Å, c=29.727(3) Å, α=81.9990(10)°, β=88.0830(10)°, γ=89.9940(10)°, V=14875(2) Å(3) . Structural analysis indicates the framework of 1 is a 3D perovskite-like structure constructed out of CO3 @Dy26 building units and Cu(+) centers by means of nicotinic acid ligand bridging. In 2, however, nanosized CO3 @Tb26 units and [Ag3 Cl](2+) centers are connected by Nic(-) bridges to give rise to a 2D structure. It is worth mentioning that this kind of 4d-4f cluster-based MOF is quite rare as most of the reported analogous compounds are 3d-4f ones. Additionally, the solid-state emission spectra of pure compound 2 at room temperature suggest an efficient energy transfer from the ligand Nic(-) to Tb(3+) ions, which we called the "antenna effect". Compound 2 shows a good two-photon absorption (TPA) with a TPA coefficient of 0.06947 cm GM(-1) (1 GM=10(-50) cm(4) s photon(-1) ), which indicates that compound 2 might be a good choice for third-order nonlinear optical materials.

Hydrothermal Synthesis, Structure and Optical Properties of Two Novel Nanosized Ln26@CO3 (Ln=Dy and Tb) Cluster‐Based Lanthanide–Transition‐Metal Organic Frameworks (Ln MOFs)

Invited for the cover of this issue is the group of Hua Mei and Yan Xu at Nanjing Tech University, China. The image depicts star-like {Tb26 } clusters, which are simplified as blue balls, and Ag atoms, which are distributed in the MOF structure uniformly to give a lanthanide-MOF structure with good optical properties. Read the full text of the article at 10.1002/chem.201405178.

Two novel mixed Eu3+/Y3+ Ln MOFs: influence of pH on the topology, Eu/Y ratio and energy transfer

Two mixed europium–yttrium MOFs with different interesting structures and doping proportions have been successfully synthesized by adjusting the pH values. The pH value largely affects the topologies and Eu/Y ratios of the two compounds.

1,4‐Phenylenediacetate‐Based Ln MOFs – Synthesis, Structures, Luminescence, and Catalytic Activity

AbstractA series of new isostructural lanthanide MOFs, [Ln2(pda)3(H2O)]·2H2O [Ln = La (1), Ce(2), Pr(3), Nd(4), Sm(5), Eu(6), Gd(7), Tb(8), Dy(9), Ho(10), Er(11), Tm(12), and Yb(13); H2dpa = 1,4‐phenylenediacetate], have been solvothermally synthesized and structurally characterized by single‐crystal (or/and powder) X‐ray diffraction analysis. All the MOFs are isostructural and consist of 1D Ln–COO helixes that are cross‐linked by the –CH2C6H4CH2– spacers of the pda2– anions in a 3D compressed honeycomb‐shaped network with 1D open channels, which accommodate guest and coordinated water molecules. Evacuation of [Ln2(pda)3(H2O)]·2H2O at 200 °C under vacuum generates [Ln2(pda)3], which gives X‐ray powder diffraction patterns consistent with those of [Ln2(pda)3(H2O)]·2H2O. MOFs 6 and 8 show characteristic luminescent properties. Activated [Tb2(pda)3] exhibits excellent catalytic performance in the heterogeneous acetalization of benzaldehyde with methanol. The possibility for easy recycling makes this catalyst a highly promising candidate to address environmental concerns.