Shu-Na Zhao

One-dimensional channel-structured Eu-MOF for sensing small organic molecules and Cu2+ ion

Two new lanthanide metal–organic frameworks Ln(FBPT)(H2O)(DMF) (FBPT = 2′-fluoro-biphenyl-3,4′,5-tricarboxylate, Ln = Eu and Tb) were prepared under solvothermal conditions. Single crystal X-ray diffraction analyses reveal that the two compounds are isostructurally related with the same one-dimensional channel structure on the basis of FBPT as an organic linker. Herein, the Eu(FBPT)(H2O)(DMF) (EuL) is selected as a representative sample for luminescent measurements. Study of the photoluminescence properties reveals that the EuL exhibits red emission, corresponding to the 5D0 → 7FJ (J = 1–4) transitions of the Eu3+ ion under UV light excitation. Most interestingly, when this compound was immersed in the different organic solvents and metal ion DMF solutions, it shows highly selective and sensitive sensing for small organic molecules and Cu2+ ions. In connection to this, a probable sensing mechanism was also discussed in this paper.

A europium(III) based metal–organic framework: bifunctional properties related to sensing and electronic conductivity

The accessible interspace of [Eu4(BPT)4(DMF)2(H2O)8] (EuL) metal–organic framework (MOF) based host materials can serve as good candidates for loading of a variety of guest molecules. In this regard, two functional properties, sensing and electronic conductivity of EuL MOF were systematically studied in this contribution. The photoluminescent properties reveal that the EuL exhibits characteristic red emission of Eu3+ ion, and presents highly detectable luminescence responses for Cu2+ ions and acetone molecules in DMF solution. For the studies of electrical properties, they were focused on the electronic conductivities of I2-incorporated EuL in anhydrous media and at different temperatures. With the increase of temperature from 25 to 80 °C, the I2-incorporated EuL showed significant changes in conductivities from 8.27 × 10−7 S cm−1 to 2.71 × 10−5 S cm−1. Meanwhile, the activation energy (Ea) was for the first time estimated for iodine-element-incorporated MOF with the help of Arrhenius plots. The successful achievements of the impedance measurements and analyses for I2-incorporated EuL prove for the first time that iodine-element-incorporated MOF can also be used for studies of conductivity under anhydrous conditions and at moderate temperature.

Encapsulation of Ln(III) Ions/Dyes within a Microporous Anionic MOF by Post-synthetic Ionic Exchange Serving as a Ln(III) Ion Probe and Two-Color Luminescent Sensors

A new anionic framework {[Me2NH2]0.125[In0.125(H2L)0.25]⋅xDMF}n (1) with one-dimensional (1D) channels along the c axis of about 13.06×13.06 Å(2), was solvothermally synthesized and well characterized. Post-synthetic cation exchange of 1 with Eu(3+), Tb(3+), Dy(3+), Sm(3+) afforded lanthanide(III)-loaded materials, Ln(3+)@1, with different luminescent behavior, indicating that compound 1 could be used as a potential luminescent probe toward different lanthanide(III) ions. Additionally, compound 1 exhibits selective adsorption ability toward cationic dyes. Moreover, the RhB@1 realized the probing of different organic solvent molecules by tuning the energy transfer efficiency between two different emissions, especially for sensing DMF. This work highlights the practical application of luminescent guest@MOFs as sensors, and it paves the way toward other one/multi-color luminescent host-guest systems by rational selection of MOF hosts and guest chromophores with suitable emissive colors and energy levels.

A Metal–Organic Framework/DNA Hybrid System as a Novel Fluorescent Biosensor for Mercury(II) Ion Detection

Mercury(II) ions have emerged as a widespread environmental hazard in recent decades. Despite different kinds of detection methods reported to sense Hg(2+) , it still remains a challenging task to develop new sensing molecules to replenish the fluorescence-based apparatus for Hg(2+) detection. This communication demonstrates a novel fluorescent sensor using UiO-66-NH2 and a T-rich FAM-labeled ssDNA as a hybrid system to detect Hg(2+) sensitively and selectively. To the best of our knowledge, it has rarely been reported that a MOF is utilized as the biosensing platform for Hg(2+) assay.

A Temperature‐Responsive Smart Europium Metal‐Organic Framework Switch for Reversible Capture and Release of Intrinsic Eu3+ Ions

Stimuli‐responsive structural transformations are emerging as a scaffold to develop a charming class of smart materials. A EuL metal‐organic framework (MOF) undergoes a reversible temperature‐stimulated single‐crystal to single‐crystal transformation, showing a specific behavior of fast capture/release of free Eu3+ in the channels at low and room temperatures. At room temperature, compound 1a is obtained with one free carboxylate group severing as further hook, featuring one‐dimensional square channels filled with intrinsic free europium ions. Trigged by lowering the ambient temperature, 1b is gained. In 1b, the intrinsic free europium ions can be fast captured by the carboxylate‐hooks anchored in the framework, resulting in the structural change and its channel distortion. To the best of our knowledge, this is the first report of such a rapid and reversible switch stemming from dynamic control between noncovalent and covalent Eu–ligand interactions. Utilizing EuL MOF to detect highly explosive 2,4,6‐trinitrophenol at room temperature and low temperature provides a glimpse into the potential of this material in fluorescence sensors.

Highly thermostable lanthanide metal–organic frameworks exhibiting unique selectivity for nitro explosives

Three isostructural 3D metal–organic frameworks [Ln(L)1.5(DEF)]n (Ln = Gd (1), Eu (2), Tb (3), H2L = 9,9-diethylfluorene-2,7-dicarboxylic acid) have been solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction. The main framework of compounds 1–3 show high thermal stability to 400 °C but with a distortion or shrinking of the crystal lattice between 200 °C and 250 °C. The high red emission intensity and the microporous instinct of the solvent-free [Eu(L)1.5]n (2a) indicate that it can be potentially used as luminescent sensor. It was then applied in the detection of organic solvent molecules. Notably, it exhibits high sensitivity for 2,4,6-trinitrophenol (TNP) with Ksv constant 6.24 × 104 M−1 through luminescence quenching experiments.

A Eu/Tb-codoped coordination polymer luminescent thermometer

A mixed-lanthanide coordination polymer Eu0.0618Tb0.9382L as a self-referenced luminescent thermometer based on the intensity ratio of the two emissions (Tb3+ at 544 nm and Eu3+ at 613 nm) is more reliable than EuL/TbL based on one emission.

Two high-connected metal–organic frameworks based on d10-metal clusters: syntheses, structural topologies and luminescent properties

The d(10)-metal-oxo clusters connected by the asymmetric tricarboxylate and linear neutral ligands give rise to two novel high-connected MOFs. They feature the highest (3,16)- and (3,8)-connected three-dimensional frameworks based on cube-like octanuclear [Zn8(μ2-OH)4(CO2)12] clusters and butterfly-like tetranuclear [Cd4(μ3-OH)2(CO2)6] clusters as the secondary building units, respectively.

An ideal detector composed of a 3D Gd-based coordination polymer for DNA and Hg2+ ion

A Gd-based coordination polymer (CP) was synthesized solvothermally with 5-triazole isopthalic acid (H2L) and Gd3+ ion. The crystal structure of GdL showed high thermal stability up to 400 °C and water stability for a wide pH range (pH 2–10). It can be noted that it showed the ability to highly quench the fluorescence and had a different affinity toward ssDNA and dsDNA. The Gd-based CP was employed as an effective fluorescent sensing platform for DNA and Hg2+ ion detection with sensitivity and selectivity.

Self-supported Co3O4 wire-penetrated-cage hybrid arrays with enhanced supercapacitance properties

Unique self-supported arrays (Co3O4 nanowire-self-penetrated-Co3O4 nanocages) on Ni foam are successfully fabricated via a metal–organic-framework (MOF)-assisted method. The as-obtained sample exhibits a remarkably enhanced supercapacitance performance.