High and Tunable Proton Conduction in Six 3D-Substituted Imidazole Dicarboxylate-Based Lanthanide-Organic Frameworks

Six isostructural three-dimensional (3D) Ln(III)-organic frameworks, {[Ln₂(HMIDC)₂(μ₄-C₂O₄)(H₂O)₃]·4H₂O}_n [Ln^III = Gd^III (1), Eu^III (2), Sm^III (3), Nd^III (4), Pr^III (5), and Ce^III (6)], have been fabricated by using a multifunctional ligand of 2-methyl-1H-imidazole-4,5-dicarboxylic acid (H₃MIDC). Ln-metal-organic frameworks (MOFs) 1-6 present 3D structures and possess abundant H-bonded networks between imidazole-N atoms and coordinated and free water molecules. All the six Ln-MOFs demonstrate humidity- and temperature-dependent proton conductivity (σ) having the optimal values of 2.01 × 10^-3, 1.40 × 10^-3, 0.93 × 10^-3, 2.25 × 10^-4, 1.11 × 10^-4, and 0.96 × 10^-4 S·cm^-1 for 1-6, respectively, at 100 °C/98% relative humidity, in the order of Ce^III (6) < Pr^III (5) < Nd^III (4) < Sm^III (3) < Eu^III (2) < Gd^III (1). In particular, the σ for 1 is 1 order of magnitude higher than that for 6, and it enhances systematically according to the decreasing order of the ionic radius, indicating that the lanthanide-contraction tactics can effectively regulate the proton conductivity while retaining the proton conduction routes. This will offer valuable guidance for the acquisition of new proton-conducting materials. In addition, the outstanding water stability and electrochemical stability of such Ln-MOFs will afford a solid material basis for future applications.

Two imidazole multicarboxylate-based MOFs: syntheses, structures and proton conductive properties

Two highly water-stable MOFs exhibited optimal σ values of around 10−4 S cm−1 at 98% RH and 100 °C, which can be compared to the values of previous MOFs.

Proton conduction in two Cu/Zn dimer-based hydrogen-bonded supramolecular frameworks from imidazole multi-carboxylate

At 98% RH and 100 °C, two dimer-based HSFs show the best σ values of 3.13 × 10⁻⁴ S cm⁻¹ for 1 and 0.55 × 10⁻⁴ S cm⁻¹ for 2, which can be compared to the values of reported HSFs.

Crystal structure of 5-carboxy-2-(2-carboxyphenyl)-1H-imidazol-3-ium-4-carboxylate dihydrate, C12H8N2O6⋅2(H2O)

C12H12N2O8, monoclinic, P21/n (no. 14), a = 5.1122(5) Å, b = 15.0150(13) Å, c = 17.3561(15) Å, β = 95.152(4)°, V = 1326.9(2) Å3, Z = 4, R gt(F) = 0.0711, wR ref(F 2) = 0.1509, T = 293(2) K.

Two zinc(ii) coordination polymers based on flexible co-ligands featuring assembly imparted sensing abilities for Cr2O7 2- and o-NP

Two new Zn(ii) coordination complexes, formulated as [Zn(opda)(pbib)] (1) and [Zn(ppda)(pbib)(H2O)] (2), (H2opda = 1,2-phenylenediacetic acid, H2ppda = 1,4-phenylene-diacetic acid, pbib = 1,4-bis(1-imidazoly)benzene), have been synthesized. The opda ligands extend a 1D chain containing (Zn-pbib) polymer chains into a 2D layer in 1. In 2, the ppda ligands link Zn(ii) atoms to form a 2D network, then the rigid bis(imidazole) ligands give rise to the 3D structure. The fluorescence property application and mechanisms of two complexes for detecting Cr2O7 2- and o-NP have been researched. For two complexes, the high quenching percentage in low concentration aqueous solution are 95.75% (Cr2O7 2-, 1), 95.28% (Cr2O7 2-, 2) and 97.56% (o-NP, 1), 96.59% (o-NP, 2). Compared with 2, complex 1 has higher quenching percentage, this could be because 1 is a 3D supramolecular with a large hole. The detection limits have been measured to be 2.992 × 10-7 M (Cr2O7 2-, 1), and 4.372 × 10-7 M (Cr2O7 2-, 2), 2.103 × 10-7 M (o-NP, 1), 1.862 × 10-7 M (o-NP, 2), respectively. The emissions of two complexes could be effectively and selectively quenched by o-NP and Cr2O7 2-, showing their potential as multi-responsive luminescent sensors.

Water-assisted proton conductivity of two highly stable imidazole multi-carboxylate-based MOFs

The proton conduction and proton mechanisms of two highly stable imidazole multi-carboxylate-based MOFs have been investigated and discussed.

Iron(iii) identification and proton conduction of a luminescent cadmium–organic framework

A luminescent metal–organic framework, [Cd(HDMPhIDC)(H₂O)]_n (1), has been successfully synthesized and structurally characterized. MOF 1 exhibits good recognition performance for Fe³⁺ ions. The recognition mechanism of Fe³⁺ was explored by UV-Vis and PXRD determinations. 1 was found to have a high proton conductivity value of 1.30 × 10⁻⁴ S cm⁻¹ at 100 °C and 98% RH.

Two luminescent transition-metal–organic frameworks with a predesigned ligand as highly sensitive and selective iron(iii) sensors

The water-stable imidazole dicarboxylated-based MOFs are excellent luminescent probes for the Fe³⁺ ion in an aqueous solution.

Construction of d10 metal coordination polymers based on in situ formed 3,5-di(1H-1,2,4-triazol-1-yl)benzoic acid from different precursors: influence of in situ hydrolysis reactions on assembly process

Seven new d¹⁰ coordination polymers based on in situ formed HDTBA from two different precursors were obtained. The influence of in situ reaction on the assembly process was explored.

Crystal structure of diaqua-(2,2′-(butane-1,4-diyl)-bis(5-carboxy-1H-imidazole-4-carboxylato)-κ4 O,O′,N,N′)cadmium(II) monohydrate, C14H18O11N4Cd

C14H18CdN4O11N4, triclinic, P1̅ (no. 2), a = 9.5135(3) Å, b = 9.8632(3) Å, c = 11.1419(4) Å, α = 83.239(1)°, β = 82.000(1)°, γ = 61.461(1)°, V = 907.93(5) Å3, Z = 2, R gt(F) = 0.0288, wR ref(F 2) = 0.0781, T = 293(2) K.

Crystal structures and luminescence properties of two Cd(II) complexes based on 2-(1H-imidazol-1-methyl)-6-methyl-1H-benzimidazole

Two new complexes, {[Cd(immb)I2]·DMF} n (1) and {[Cd3(immb)(btc)2]·H2O} n (2) (immb = 2-(1H-imidazol- 1-methyl)-6-methyl-1H-benzimidazole, btc = 1,2,3-benzenetricarboxylate, DMF = dimethyl formamide), have been synthesized and characterized. Single crystal X-ray diffraction shows that 1 exhibits a chain structure constructed by immb ligands bridging Cd(II) ions. In 2, Cd(II) ions are linked by immb ligands with bridging mode and btc3– anions with the μ 2-η 2:η 1 bonding pattern leading to a 2D structure. Luminescent properties have been investigated in the solid state at room temperature.

Synthesis, structures, luminescent and molecular recognition properties of three new alkaline earth metal carboxyphosphonates with a 3D supramolecular structure

Three new alkaline earth metal carboxyphosphonates with a 3D supramolecular structure, namely, Ca[(H₃L)(H₂O)] (1), Sr[(H₃L)(H₂O)₂] (2) and Ba₂[(H₃L)₂(H₂O)₄] (3) have been hydrothermally synthesized. The luminescent and molecular recognition properties of compounds 1–3 were investigated.