Fangna Dai

Lanthanide metal–organic frameworks containing a novel flexible ligand for luminescence sensing of small organic molecules and selective adsorption

Five lanthanide metal–organic frameworks, [Ln(L)(H2O)(NMP)]·1.5H2O (Ln = Ce (1), Pr (2); H3L = 1,3,5-tris(4-carboxyphenyl-1-ylmethyl)-2,4,6-trimethylbenzene), and [Ln2(L)2(H2O)3]·2H2O (Ln = Eu (3), Tm (4), Yb (5)), have been synthesized and characterized. Complexes 1–5 exhibit similar 1D channels through the linkage of Ln-carboxylate chains with the backbones of H3L ligands. The channels for complexes 1 and 2 are occupied by coordinated NMP molecules. 3 shows potential application for the luminescence sensing of small organic molecules. Moreover, 5 exhibits selective adsorption of CO2 over N2 and CH4 and catalytic activities toward the cyanosilylation reaction.

A multifunctional Eu MOF as a fluorescent pH sensor and exhibiting highly solvent-dependent adsorption and degradation of rhodamine B

Due to their tunable structure and porosity, metal–organic frameworks have provided a new platform for fluorescence sensing and adsorption/separation of gas or organic molecules. Many studies have focused on sensing metal ions, anions, or organic molecules through fluorescence quenching or enhancement of MOFs, but studies on pH-fluorescence sensors are seldom reported. Furthermore, highly solvent-dependent adsorption and degradation of dye molecules based on functional MOFs has not been explored to date. In this study, we describe a multifunctional Eu MOF, [H3O][Eu3(HBPTC)2(BPTC)(H2O)2]·4DMA (UPC-5, UPC = China University of Petroleum [East China]) based on a tetracarboxylate ligand. The luminescence intensity of UPC-5 is strongly correlated with the pH value in the pH range from 7.5 to 10.0, and a linear relationship between pH value and fluorescent intensity is observed. Another attractive property of UPC-5 is that its Li-exchanged form, Li-UPC-5, possesses solvent-dependent adsorption and degradation of rhodamine B. The highly efficient degradation or decolorization of rhodamine B with long-term stability and activity gives Li-UPC-5 a potential advantage in treating rhodamine B pollution.

Improving the Porosity and Catalytic Capacity of a Zinc Paddlewheel Metal-Organic Framework (MOF) through Metal-Ion Metathesis in a Single-Crystal-to-Single-Crystal Fashion

Zinc paddlewheel metal-organic frameworks (MOFs) frequently exhibit low stability or complete collapse upon the removal of axial ligands. Hence, there are very few reports on gas adsorption of zinc paddlewheel MOFs. In this work, the N2 and H2 adsorption measurements were carried out for a zinc MOF (namely, SDU-1) based on two types of paddlewheel secondary building units (SBUs): [Zn2(COO)3] and [Zn2(COO)4]. Because of the existence of inherent surface instability upon removal of solvates in zinc paddlewheel SBU, SDU-1 possesses a very low surface area. Through metal-ion metathesis in a single-crystal-to-single-crystal fashion, the Zn(2+) ions in SDU-1 were exchanged by Cu(2+) ions to generate Cu-SDU-1. Through the measurements of gas adsorption and catalytic test, the porosity and catalytic capacity of Cu-SDU-1 have been improved significantly, compared to SDU-1.

Pentiptycene-Based Luminescent Cu (II) MOF Exhibiting Selective Gas Adsorption and Unprecedentedly High-Sensitivity Detection of Nitroaromatic Compounds (NACs)

The assembly of a fluorescent pentiptycene-based ligand with copper ion resulted in the formation of a 3D porous metal-organic framework (UPC-21) based on well-known paddlewheel SBUs. UPC-21 exhibits selective adsorption of CO2 over CH4 and N2 at 273 K and 295 K, C2H2 over CH4 at 273 K. The most significant performance of UPC-21 is its highly efficient detection of NACs such as 4-NP, 1,4-DNB, NB, and 1,3-DNB with the calculated quenching constants, Ksv, being 3.097 × 106, 1.406 × 106, 4.420 × 105, and 1.498 × 105 M−1 for 4-NP, 1,4-DNB, NB, 1,3-DNB, respectively, which keeps a record on the fluorescence detection of NACs. This is the first porous Cu(II) MOF that exhibits fluorescent detection of NACs with high sensitivities.

Tuning the Dimensionality of Interpenetration in a Pair of Framework-Catenation Isomers To Achieve Selective Adsorption of CO2 and Fluorescent Sensing of Metal Ions

A pair of framework-catenation isomers (UPC-19 and UPC-20) based on an anthracene-functionality dicarboxylate ligand were synthesized and characterized for the first time through tuning of the dimensionality of interpenetration. The interpenetration dimensionality significantly influences the properties including the porosity, gas-uptake capacity, and fluorescent sensing ability: UPC-19 with 5-fold interpenetration is nonporous, whereas the 3-fold interpenetration form of UPC-20 is porous and exhibits selective adsorption of CO2 and fluorescent sensing of Cu(2+) and Fe(3+) through fluorescence quenching.

Cyclodextrin-Based Metal-Organic Nanotube as Fluorescent Probe for Selective Turn-On Detection of Hydrogen Sulfide in Living Cells Based on H2S-Involved Coordination Mechanism.

Hydrogen sulfide (H2S) has been considered as the third biologically gaseous messenger (gasotransmitter) after nitric oxide (NO) and carbon monoxide (CO). Fluorescent detection of H2S in living cells is very important to human health because it has been found that the abnormal levels of H2S in human body can cause Alzheimer’s disease, cancers and diabetes. Herein, we develop a cyclodextrin-based metal-organic nanotube, CD-MONT-2, possessing a {Pb14} metallamacrocycle for efficient detection of H2S. CD-MONT-2′ (the guest-free form of CD-MONT-2) exhibits turn-on detection of H2S with high selectivity and moderate sensitivity when the material was dissolved in DMSO solution. Significantly, CD-MONT-2′ can act as a fluorescent turn-on probe for highly selective detection of H2S in living cells. The sensing mechanism in the present work is based on the coordination of H2S as the auxochromic group to the central Pb(II) ion to enhance the fluorescence intensity, which is studied for the first time.

Expanded Porous Metal-Organic Frameworks by SCSC: Organic Building Units Modifying and Enhanced Gas-Adsorption Properties.

Two amino-functional copper metal-organic frameworks of formula [Cu3(ATTCA)2(H2O)3]·2DMF·11H2O·12EtOH (1) (H3ATTCA = 2-amino-[1,1:3,1-terphenyl]-4,4,5-tricarboxylic acid, pyz = pyrazine, DMF = dimethylformamide) and [Cu3(ATTCA)2(pyz)(H2O)]·2DMF·12H2O·8EtOH (2) were synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction, infrared spectroscopy, elemental analyses, thermogravimetric analyses, and powder X-ray diffraction. Single-crystal X-ray diffraction analysis revealed that both complexes 1 and 2 are built of the Cu2(COO)4 paddlewheel secondary building units with an fmj topology. Importantly, complex 1 can be transformed into complex 2 by the single-crystal to single-crystal transformation of which the coordinated water molecules are replaced with pyz molecules. However, the adsorption abilities of 2 are obviously lower than those of 1, as its pores are partially blocked by pyz molecules. Moreover, gas-adsorption analysis showed that the amino-functional 1 possesses higher gas-adsorption capacity than UMCM-151 for N2, H2, CH4, and C2H2, especially for CO2.

Fluorescent selectivity for small molecules of three Zn-MOFs with different topologies based on a tetracarboxylate ligand

Three new metal–organic frameworks (MOFs) constructed from terphenyl-3,3′′,5,5′′-tetracarboxylic acid (H4ptptc) and zinc nitrate, [Zn2(ptptc)(DMF)3]·4H2O·5.5DMF (1), [Zn2(ptptc)(DMA)(H2O)]·2.5H2O·3.5DMA (2) and [Zn(ptptc)0.5(H2O)]·DMF·DMA (3), have been obtained and characterized. All the complexes exhibit 3D 4-connected networks with different topologies involving diamond (dia, for 1), lonsdaleite (lon, for 2) and Nbo (for 3), which emanate from the different reaction solvents (DMF, DMA and mixture of DMF/DMA (1 : 1), respectively). The results of photoluminescence properties show that the three complexes can be act as potential luminescent probes or sensors for detecting small organic molecules and toxic substances.

A Zn Metal-Organic Framework with High Stability and Sorption Selectivity for CO2.

A three-dimensional porous Zn metal-organic framework (UPC-12) with high thermal and chemical stability was isolated in high yield and purity from a hydrothermal reaction. UPC-12 exhibits high selectivity for CO2 due to the formation of hydrogen bonds between CO2 molecules and the -COOH groups exposed inside the channels and the effective π-π interactions between CO2 molecules and the pillared bipyridine moieties of the MOF. The adsorption-desorption process was studied, for the first time, by both (13)C CP-TOSS NMR spectroscopy and in situ DRIFTS.

A visual test paper based on Pb(II) metal–organic nanotubes utilized as a H2S sensor with high selectivity and sensitivity

The fluorescent Pb(II)–metal–organic nanotube, CD-MONT-2, which possesses a large {Pb14} metallamacrocycle, is synthesized by a modified biphasic liquid–solid–liquid (BLSL) strategy. This strategy takes advantage of solid cyclohexanol to avoid generation of by-products, and is suitable for producing CD-MONT-2 on a large scale. Importantly, water-stable CD-MONT-2 can be easily made into H2S test papers by coating a solution mixture of sodium carboxymethyl cellulose and CD-MONT-2′ on glass plates, which have the characteristics of high efficiency, rapidity, and visualization based on its fluorescence “turn-off” response. The CD-MONT-2 based visual test papers can be used without pretreatment and possess excellent sensitivity and stability.