Lanthanide–organic frameworks for gas storage and as magneto-luminescent materials

Self-cleaning MOF: realization of extreme water repellence in coordination driven self-assembled nanostructures

Bio-inspired self-cleaning surfaces have found industrial applications in oil-water separation, stain resistant textiles, anti-biofouling paints in ships etc. Interestingly, self-cleaning metal-organic framework (MOF) materials having high water contact angles and corrosion resistance have not been realized so far. To address this issue, we have used the fundamentals of self-assembly to expose hydrophobic alkyl chains on a MOF surface. This decreases the surface free energy and hence increases hydrophobicity. Coordination directed self-assembly of dialkoxyoctadecyl-oligo-(p-phenyleneethynylene)dicarboxylate (OPE-C18 ) with ZnII in a DMF/H2O mixture leads to a three dimensional supramolecular porous framework {Zn(OPE-C18)·2H2O} (NMOF-1) with nanobelt morphology. Inherently superhydrophobic and self-cleaning NMOF-1 has high thermal and chemical stability. The periodic arrangement of 1D Zn-OPE-C18 chains with octadecyl alkyl chains projecting outward reduces the surface free energy leading to superhydrophobicity in NMOF-1 (contact angle: 160-162°). The hierarchical surface structure thus generated, enables NMOF-1 to mimic the lotus leaf in its self-cleaning property with an unprecedented tilt angle of 2°. Additionally, superhydrophobicity remains intact over a wide pH range (1-9) and under high ionic concentrations. We believe that such a development in this field will herald a new class of materials capable of water repellent applications.

Observation of cascade f → d → f energy transfer in sensitizing near-infrared (NIR) lanthanide complexes containing the Ru(ii) polypyridine metalloligand

A possible approach to achieve multiple f → d, d → f and cascade f → d → f energy transfer processes in heteronuclear Ru–Ln and Ln1–Ru–Ln2 complexes.

A postsynthetically modified MOF hybrid as a ratiometric fluorescent sensor for anion recognition and detection

MIL-125(Ti)-AM-Eu, which is derive from MIL-125(Ti)-NH₂ by covalent postsynthetic modification, is synthesized and exhibit excellent photoluminescence features. It have been designed to be a ratiometric fluorescent sensor (I_L/I_Eu) for sensitively detecting phosphate and oxalate with a proposed dual-readout orthogonal identification pattern.

Lanthanide-based metal–organic frameworks as luminescent probes

We discuss the construction of lanthanide-based metal–organic frameworks, their applications in possible detection mechanisms, and summarize some examples of Ln-MOFs as luminescent probes.

High CO2 /CH4 Selectivity of a Flexible Copper(II) Porous Coordination Polymer under Humid Conditions

The development of highly efficient CO₂ separation materials is very important for environmental preservation and energy conservation. Crystalline porous coordination polymers (PCPs)/metal-organic frameworks are one of a number of promising types of porous materials for CO₂ separation because of their controllable pore size, shape and surface function. Simultaneously, the unique structural flexibility of PCPs affords both high CO₂ selectivity and inexpensive regeneration. However, this family of materials suffers from the coexistence of water that destroys the framework of PCPs and its adsorption in the pores is greater than that of CO₂ , which results in a deterioration in CO₂ -separation performance. Herein, a flexible and hydrophobic Cu^II PCP that is stable towards water has been designed and synthesised. This PCP has extremely high adsorption selectivity for CO₂ over CH₄ , derived from its structural flexibility. Furthermore, the obtained water-tolerant flexible PCP, under CO₂ /CH₄ mixed-gas conditions, exhibits highly selective CO₂ adsorption over CH₄ , even in the presence of water.

Carbon Dioxide Capture by a Metal-Organic Framework with Nitrogen-Rich Channels Based on Rationally Designed Triazole-Functionalized Tetraacid Organic Linker

A semirigid tetraacid linker H4L functionalized with 1,2,3-triazole was rationally designed and synthesized to access nitrogen-rich MOFs for selective adsorption of CO2. The cadmium MOF, that is, Cd-L, obtained by the reaction of H4L with Cd(NO3)2, is found to be a 3D porous framework structure that is robust to desolvation. Crystal structure analysis reveals channels that are decorated by the triazole moieties of L. Gas adsorption studies show that Cd-L MOF permits remarkable CO2 uptake to the extent of 99 and 1000 cc/g at 1 and 30 bar, respectively, at 0 °C. While literature survey reveals that MIL-112, constructed from a 1,2,3-triazole functionalized linker, exhibits no porosity to gas adsorption due to structural flexibility, the results with Cd-L MOF described herein emphasize how rigidification of the organic linker improves gas uptake properties of the resultant MOF.

Solvent-Induced Change of Electronic Spectra and Magnetic Susceptibility of Co(II) Coordination Polymer with 2,4,6-Tris(4-pyridyl)-1,3,5-triazine

One-dimensional coordination polymer [Co(Piv)2(4-ptz)(C2H5OH)2]n (compound 1, Piv(-) = pivalate, 4-ptz = 2,4,6-tris(4-pyridyl)-1,3,5-triazine) was synthesized by interaction of Co(II) pivalate with 4-ptz. Desolvation of 1 led to formation of [Co(Piv)2(4-ptz)]n (compound 2), which adsorbed N2 and H2 at 78 K as a typical microporous sorbent. In contrast, absorption of methanol and ethanol by 2 at 295 K led to structural transformation probably connected with coordination of these alcohols to Co(II). Formation of 2 from 1 was accompanied by change of color of sample from orange to brown and more than 2-fold decrease of molar magnetic susceptibility (χM) in the temperature range from 2 to 300 K. Resolvation of 2 by ethanol or water resulted in restoration of spectral characteristics and χM values almost to the level of that of 1. χMT versus T curves for 1 and samples, obtained by resolvation of 2 by H2O or C2H5OH, were fitted using a model for Co(II) complex with zero-field splitting of this ion.

Eu(III)-functionalized MIL-124 as fluorescent probe for highly selectively sensing ions and organic small molecules especially for Fe(III) and Fe(II)

A layerlike MOF (MIL-124, orGa2(OH)4(C9O6H4)) has been prepared and chosen as a parent compound to encapsulate Eu(3+) cations by one uncoordinated carbonyl group in its pores. The Eu(3+)-incorporated sample (Eu(3+)@MIL-124) is fully characterized, which shows excellent luminescence and good fluorescence stability in water or other organic solvents. Subsequently, we choose Eu(3+)@MIL-124 as sensitive probe for sensing metal ions, anions, and organic small molecules because of its robust framework. Studying of the luminescence properties reveals that the complex Eu(3+)@MIL-124 was developed as a highly selective and sensitive probe for detection of Fe(3+) (detection limit, 0.28 μM) and Fe(2+) ions through fluorescence quenching of Eu(3+) and MOF over other metal ions. In connection to this, a probable sensing mechanism was also discussed in this paper. In addition, when Eu(3+)@MIL-124 was immersed in the different anions solutions and organic solvents, it also shows highly selective for Cr2O7(2-)(detection limit, 0.15 μM)and acetone. Remarkably, it is the first Eu-doped MOF to exhibit an excellent ability for the detection of Fe(3+) and Fe(2+) in an aqueous environment without any structural disintegration of the framework.

Mesoxalate as Cu(ii)–Ln(iii) linker in the construction of MOFs in DMSO/water medium

The combination of [Cu₃(Hmesox)₃]³⁻ with La(iii), Ce(iii), Pr(iii), Nd(iii) and Eu(iii) in DMSO/H₂O yields 3d–4f heterometallic metal–organic frameworks, with the dimensionality of the network being controlled by the coordination number of the Ln(iii) ion.

Two dimethylphenyl imidazole dicarboxylate-based lanthanide metal–organic frameworks for luminescence sensing of benzaldehyde

Two novel dimethylphenyl imidazole dicarboxylate-based lanthanide(iii)-organic frameworks, [Ln(H₂DMPhIDC)₃(H₃DMPhIDC)]_n (Ln = Eu (1), Tb (2); H₃DMPhIDC = 2-(3,4-dimethylphenyl)-1H-imidazole-4,5-dicarboxylic acid) have been synthesized under hydrothermal conditions.

The first example of Tb3-containing metallopolymer-type hybrid materials with efficient and high color-purity green luminescence

In the obtained Tb³⁺-based efficient (Φ_overall = 76–83%) and high color-purity green luminescent 3@PMMA from doping and metallopolymer-type Poly(NBE-3), grafting endows a higher-concentration self-quenching.

Luminescent zinc metal–organic framework (ZIF-90) for sensing metal ions, anions and small molecules

We synthesize ZIF-90, which exhibits an intense blue luminescence excited under visible light. Luminescent studies indicate that ZIF-90 could be an efficient multifunctional fluorescence material for sensing metal cations, anions and organic small molecules.

Slow magnetic relaxation in a lanthanide helix chain compound [Dy(HNA)(NA)2(NO3)]n (HNA = nicotinic acid)

A racemic helix chain Dy³⁺ compound 1 bridged by μ_1,3-COO groups was synthesized, which showed slow magnetic relaxation behaviour.

Controlling dimensionality via a dual ligand strategy in Ln-thiophene-2,5-dicarboxylic acid-terpyridine coordination polymers

Eleven new lanthanide-2,5-TDC-terpyridine coordination polymers which employ a dual ligand strategy have been synthesized and characterized by single crystal and powder X-ray diffraction as well as luminescence spectroscopy.

4-(4-Carboxyphenoxy)phthalate-based coordination polymers and their application in sensing nitrobenzene

Structural characterization of 4-(4-carboxyphenoxy)phthalate-based Cd²⁺ and Mn²⁺ coordination polymers are reported, and Cd²⁺ coordination polymer can serve as probe to sense nitrobenzene.

Tunable emission in lanthanide coordination polymer gels based on a rationally designed blue emissive gelator

A new blue emissive gelator has been synthesized and its self-assembly with Tb^III and Eu^III results in coordination polymer gels, which show tunable emission based on stoichiometric control over LMWG:Tb^III:Eu^III.

Syntheses, structures, and magnetic properties of homodinuclear lanthanide complexes based on dinucleating Schiff base ligands

Two series of homodinuclear lanthanide(iii) complexes were synthesized and characterized. Magnetic studies reveal the weakly antiferromagnetic coupling between paramagnetic Ln ions and enhanced relaxation of magnetization for Dy₂ complexes.

Lanthanide(iii) morpholine 4-dithiocarbamate complexes: Pr(iii) derivative shows first example of polymeric lanthanide(iii) dithiocarbamate

Polymeric and discrete Ln(iii) morpholine 4-dithiocarbamate complexes [Ln(Phen)(Mph-Dtc)₃]x·CH₂Cl₂ [Ln = Pr (1), Nd (2) and Eu (3); Mph-Dtc = morpholine 4-dithiocarbamate; x = 2 (1) or 1 (2, 3)] have been synthesized and characterized.

Three sra topological lanthanide–organic frameworks built from 2,2′-dimethoxy-4,4′-biphenyldicarboxylic acid

The first neutral 3D sra-LOF built from a 1D inorganic rod-shaped chain [Ln(CO₂)₂(HCO₂)]_n (Ln = Eu, Gd, Dy) was synthesized.

A bimodal anionic MOF: turn-off sensing of CuII and specific sensitization of EuIII

A bimodal anionic MOF is reported which acts as a turn-off Cu^II sensor as well as a specific Eu^III sensitizer via cation exchange.