Azobenzenetetracarboxylic Acid Research Articles

Impact of Synthetic Variables on the Structural Diversity of TbIII-Carboxylate Frameworks: Gas Adsorption, Magnetism, and Organocatalysis Investigations.

In this work, three unique TbIII-carboxylate frameworks with the formula {[Tb2(OH)2(H2O)2(abtc)]·2H2O}n (1), {[Tb2(abtc)1.5(H2O)3(DMA)]·H2O}n (2) and {[Tb3(abtc)2.5(H2O)4]·H3O}n (3), each displaying structural variations, have been successfully synthesized by the solvothermal reactions of Tb(NO3)3·6H2O with the azo-containing ligand 3,3',5,5'-azobenzene tetracarboxylic acid (H4abtc) under varying conditions. Detailed single-crystal X-ray diffraction (SC-XRD) analysis manifested a remarkable diversity in these structures, demonstrating various coordination patterns of TbIII-metal nodes with the carboxylate groups of the organic linker, which contributed to the generation of intricate three-dimensional (3D) coordination networks with remarkable chemical resistance. Furthermore, frameworks 2 and 3, characterized by porous networks containing two and three independent TbIII-metal nodes, respectively, were both demonstrated to be efficient heterogeneous catalysts toward the cyanosilylation of imines under mild conditions with excellent reusability. In addition, direct current (Dc) magnetic susceptibility measurements conducted on frameworks 1, 2, and 3 indicated that there were obvious antiferromagnetic interactions among the TbIII-metal nodes, which suggests the involvement of intricate intra- and intertrimer exchange channels, adding another fascinating dimension to their physical properties.

Adsorptive degradation of dimethyl methylphosphonate over Zr-based metal–organic framework built from 3,3′,5,5′-azobenzenetetracarboxylic acid

Chemical warfare agents (CWAs) pose a significant threat to humans because of their high toxicity. Zirconium-based metal–organic frameworks (Zr-MOFs) are promising candidates for the purification and detoxification of CWAs. In this study, we prepared a Zr6O4(OH)8(H2O)4(abtc)2 denoted to Zr-abtc (abtc = 3,3′,5,5′-azobenzene-tetracarboxylate) under eco-friendly hydrothermal reflux conditions and investigated its detoxification performance. Dimethyl methylphosphonate (DMMP) was used as a simulant of a nerve agent to evaluate the adsorption performance of Zr–abtc. The Zr–abtc MOF was constructed from an 8-connected Zr6 cluster [Zr6(µ3-O)4(µ3-OH)4] with abtc as a linker, resulting in the generation of abundant surface hydroxyl groups, high porosity, and remarkable structural robustness under high moisture and high temperature conditions. The results of the breakthrough (BT) test of DMMP under dry and humid conditions reveal that Zr–abtc displays high DMMP adsorption performance with the adsorption capacity of 1.74 and 1.60 mmol/g under dry and humid condition, respectively. The high performance of Zr–abtc can be attributed to not only the strong interaction between the surface hydroxyl group of Zr–abtc MOF and DMMP but also the catalytic activity of the surface hydroxyl group to form the decomposed product of DMMP, as demonstrated using Fourier transform infrared spectroscopy (FTIR).

Reversible Structural Transformation and Catalytic Potential of Lanthanide-Azobenzenetetracarboxylates.

Inspired by the catalytic potential of lanthanide coordination polymers of 3,3',5,5'-azobenzenetetracarboxylic acid (H4abtc), two new isostructural [Ln2III(Habtc)2(DMSO)4]·DMSO·H2O (LnIII = SmIII (I), EuIII = (II), DMSO = dimethyl sulfoxide) were synthesized and characterized. Their single-crystal structures were elucidated and described. Structural transformations of II in the solid state prompted by ligand substitution and thermal treatment were studied, from which genuine reversible transformation of II to [EuIII(Habtc)(H2O)4]·3H2O (II') and [EuIII(Habtc)(H2O)2]·2H2O (II″) was revealed. This illustrates the rare case of reversible transformation in lanthanide coordination polymers. The transformation between II' and II″ was also investigated. Structural transformations among these frameworks are discussed with regard to the coordination environment of EuIII, coordination modes of Habtc3-, and similarities and disparities in framework architecture and registration. In addition, the catalytic performance of II with and without the prior activation in CO2 cycloaddition reaction with epichlorohydrin was studied in comparison with II' and II″. The excellent performance of II disregarding the activation process has been demonstrated with the maximum turnover number and turnover frequency of 7682 and 1921 h-1, respectively, for the activated II and 7142 and 1786 h-1, respectively, for the nonactivated II. The maintenance of the catalytic efficiency over 10 cycles of the catalysis and the regeneration process is illustrated and discussed with respect to structural transformation.

A Scandium‐based Microporous Metal‐Organic Framework for Ethane‐Selective Separation

AbstractPurification of ethylene (C2H4) is one of the most important industrial separation practices. In this report, Sc‐abtc, a rare‐earth microporous metal‐organic framework was successfully constructed from 3,3’,5,5’‐azobenzenetetracarboxylic acid (H4abtc) and scandium through facile solvothermal method. Sc‐abtc have shown preferrential adsorption of ethane over ethylene with 4.28 mmol g−1 uptake of ethane at ambient conditions. The calculated isosteric heat of adsorption revealed Sc‐abtc has stronger binding affinity toward C2H6 (28.2 kJ mol−1) than C2H4 (11 kJ mol−1), which revealled the mechanism of the ethane‐selective property. Moreover, column breakthrough tests were conducted to further verified the practical C2H4/C2H6 separation with excellent cycling stability.

Evaluating the High-Pressure Volumetric CH4, H2, and CO2 Storage Properties of Denser-Version Isostructural soc-Metal–Organic Frameworks

The MOF platform based on soc topology showed recent developments for gas storage applications. soc-MOFs with very open structures, such as Al-soc-MOF-1, exhibited promising gravimetric storage performance but with compromised volumetric capacities. However, the volumetric capacity is a critical parameter to consider for vehicles such as trucks. The practical constraints under such circumstances are mainly linked to the tank volume required to accommodate adsorbents. In this work, the gas storage performances of dense soc-MOFs assembled from different metal precursors and 3,3′,5,5′-azobenzene tetracarboxylic acid, denoted as In-soc-MOF-1a, In-soc-MOF-1b, In-soc-MOF-1c, Ga-soc-MOF-1a, Fe-soc-MOF-1a, Fe-soc-MOF-1b, and Al-soc-MOF-1d, with 1a, 1b, 1c, and 1d representing NO3–, Cl–, Br–, and HO– counterions, respectively, were evaluated. Using the crystallographic densities of each MOF, volumetric uptakes were calculated from gravimetric values. The volumetric CH4, H2, and CO2 uptakes of the soc-MOFs showed a gain in storage capacity upon using denser versions, with a higher CH4 uptake of Fe-soc-MOF-1b (128 g L–1 at 50 bar) than the extended analogs (∼120 g L–1 for Fe-PBPTA-soc-MOF). The counteranions were also observed to have an impact on the volumetric capacities, with In-soc-MOF-1c > In-soc-MOF-1b > In-soc-MOF-1a for CH4 and the reverse order for H2 capacities. The performances are also comparable to those of most of the previously reported benchmark MOFs.

Large scale synthesis and propylene purification by a high-performance MOF sorbent Y-abtc

Olefin/Paraffin separation, especially propylene purification from propane, is of extreme commercial importance as it produces chemical feedstock for synthetic plastics such as polypropylene. As an alternative to cryogenic distillation commonly used to purify these mixtures, the use of solid porous materials for adsorptive separation offers a more energetically efficient route. Metal-Organic Frameworks (MOFs) have shown great promise as adsorptive separation candidates in recent years. However, reports of these materials for the purification of C3 hydrocarbons exclusively provide insight of their performance in small scale laboratory settings. Single component isotherms and breakthrough curves are typically tested in the milligrams to gram scale. Herein, we present a scale-up, one-pot synthesis of a robust MOF with high propylene/propane selectivity. The organic linker 3,3′,5,5′-azobenzene-tetracarboxylic acid (H4abtc) and its yttrium-based MOF, Y-abtc, are both synthesized at the hundred-gram scale. Furthermore, we perform large-scale breakthrough experiments at the same scale. Our results show that Y-abtc samples synthesized from the one-pot 100 g scale reactions retain high crystallinity and size-exclusion based mechanism for the separation of propane/propylene mixtures. The same polymer-grade purity of propylene (>99.5%) is achieved as in the case of small scale (∼1 g) experiments.

A Comparison of Structure Determination of Small Organic Molecules by 3D Electron Diffraction at Cryogenic and Room Temperature

3D electron diffraction (3D ED), also known as micro-crystal electron diffraction (MicroED), is a rapid, accurate, and robust method for structure determination of submicron-sized crystals. 3D ED has mainly been applied in material science until 2013, when MicroED was developed for studying macromolecular crystals. MicroED was considered as a cryo-electron microscopy method, as MicroED data collection is usually carried out in cryogenic conditions. As a result, some researchers may consider that 3D ED/MicroED data collection on crystals of small organic molecules can only be performed in cryogenic conditions. In this work, we determined the structure for sucrose and azobenzene tetracarboxylic acid (H4ABTC). The structure of H4ABTC is the first crystal structure ever reported for this molecule. We compared data quality and structure accuracy among datasets collected under cryogenic conditions and room temperature. With the improvement in data quality by data merging, it is possible to reveal hydrogen atom positions in small organic molecule structures under both temperature conditions. The experimental results showed that, if the sample is stable in the vacuum environment of a transmission electron microscope (TEM), the data quality of datasets collected under room temperature is at least as good as data collected under cryogenic conditions according to various indicators (resolution, I/σ(I), CC1/2 (%), R1, Rint, ADRA).

Precise Construction of Stable Bimetallic Metal–Organic Frameworks with Single-Site Ti(IV) Incorporation in Nodes for Efficient Photocatalytic Oxygen Evolution

Precise Construction of Stable Bimetallic Metal–Organic Frameworks with Single-Site Ti(IV) Incorporation in Nodes for Efficient Photocatalytic Oxygen Evolution

Two metal-coordination polymers: Photocatalytic hydrogen production and clinical nursing value on gastric cancer combined with hyperthermic intraperitoneal chemotherapy by inducing induce oxidative stress response.

Two new coordination polymers (CPs) of {[Dy2(abtc)1.5(H2O)3(DMA)]·H2O·DMA}n (1; DMA=N,N-dimethylacetamide) and [NH2(CH3)2][Ni1.5(abtc)]·H2O (2) were synthesized through utilizing 3,3',5,5'-azobenzenetetracarboxylic acid (H4abtc) as an organic connector with the solvothermal reaction conditions. The HOMO-LUMO gap for ultra-stable complex 1 is 2.16eV through the detection of the ultraviolet-visible spectrum with an absorption edge of 570nm. The complex 1 reveals high catalytic effect for the ultraviolet-visible photocatalytic production of hydrogen, which is due to its light collection of the ligand with dye-like and porous architecture. Furthermore, the promotion effect of compounds 1 and 2 against the gastric cancer treatment was assessed when combined with intraperitoneal hyperthermia. Firstly, the inhibition of compounds 1 and 2 against the invasion and migration of cancer cells was evaluated with transwell assay. Moreover, the genes relative expression levels related with the reactive oxygen species (ROS) production in the cancer cells were also measured with real time reverse transcription-polymerase chain reaction (RT-PCR).

A new porous cationic metal–organic framework: selective sorption of organic dyes and treatment on neural stem cells during spinal cord injury treatment

A novel metal–organic framework containing Co(II) of {(Me2NH2)4[Co12(OH)4(abtc)6 (H2O)12]·14H2O}n (1) has been synthesized via Co(NO3)2·6H2O to react with the 3,3′,5,5′-azobenzenetetracarboxylic acid (H4abtc) ligand under solvothermal conditions. Furthermore, methylene blue (MB) can easily replace free cations; after half a day, more than 90% of the MB (10−5 M) is absorbed selectively, and it makes the title compound become a good medium for the separation and adsorption of the dye. In biological section, the enhancement activity of the compound on the nerve growth factor for the spinal cord injury treatment was evaluated. The relative gene expression of trkA receptor was measured with reverse transcription polymerase chain reaction. In addition to this, the activation of PI3K/Akt signaling pathway in neural stem cells after treated by compound was evaluated with western blot. The results of potential binding models were predicted by molecular docking, and the binding poses provided possible binding mechanisms of the functional groups of the complex to the TRKA protein.

RETRACTED: Two Zn(II) coordination polymers: Luminescent sensing property and treatment capacity against stable coronary heart disease by regulating E.coli abundance and IL-17 content

Abstract Two new Zn(II)-containing coordination polymers of {[NH2(CH3)2][Zn1.5(abtc)]·H2O}n (1) and {[Zn2(abtc)(DMF)3]·3DMF}n (2) have been produced under the solvothermal conditions by using the 3,3′,5,5′-azobenzenetetracarboxylic acid ligand in different solvent systems. Complex 1 and complex 2 can use as the luminescence sensors for the detection of Fe3+ which have high selectivity and sensitivity. Furthermore, the mechanism for the luminescent sensing of Fe3+ was also suggested. In the bio-research, the treatment activity for compounds 1 and 2 on SCAD was assessed through serious researches and the specific mechanism was discussed as well. After the construction of the SCAD rat model, the 5 ​mg/kg compounds 1 and 2 was given to the rats for treatment. The ELISA detection kit was used for the IL-17 content detection in the plasma of different groups. And, the abundance of the E.coli in the intestinal flora was detected with RT-PCR.

Topology-Guided Design for Sc-soc-MOFs and Their Enhanced Storage and Separation for CO2 and C2-Hydrocarbons.

Evaluating the effect of ligand substitution on metal ions and/or clusters during the MOF growth process is conducive to rational design of isoreticular MOFs with improved performance. Through topological direction and ligand substitution strategy, we herein constructed two Sc-soc-MOFs (Sc-EBTC and Sc-ABTC) based on two similar rectangular-planar diisophthalate ligands, linear-shaped H4EBTC (1,1'-ethynebenzene-3,3',5,5'-tetracarboxylic acid) and zigzag-shaped H4ABTC (3,3',5,5'-azobenzenetetracarboxylic acid), under solvothermal conditions with formic acid as a modulator. {Sc[(Sc3O)(H2O)3]3(EBTC)6} (Sc-EBTC) possesses two distinct clusters as SBUs, trinuclear [Sc3O(CO2)6] (SBU1) and mononuclear cluster [ScO6] (SBU2), which maintain the soc-topology except for the mononuclear [ScO6] instead of the corresponding trinuclear [Sc3O(CO2)6] in Sc-ABTC ({(Sc3O)(H2O)3(ABTC)1.5(NO3)}). Notably, Sc-EBTC represents a rare soc-MOF with two distinct clusters as SBUs. Due to similar pore spaces, the two Sc-soc-MOF materials both exhibit enhanced and comparable gas sorption and selectivity performances. Specially, their remarkable C2H2, C2H4, and CO2 storage capacity along with prominent CO2/CH4 and C2-hydrocarbons/CH4 separations indicate that these Sc-soc-MOFs are promising adsorbents for natural gas purification under ambient conditions.

Enhanced stability and solar cell performance via π-conjugated Lewis base passivation of organic inorganic lead halide perovskites

Abstract High power conversion efficiency (PCE) and good long-term stability of the perovskite solar cell (PSC) are two important factors on its commercial applications. Here, we propose a simple way to improve the PSC performance by adding 3,3′,5,5′-azobenzene-tetracarboxylic acid (H4abtc) into the lead iodide (PbI2) precursor solution with Lewis acid-base adduct via two-step solution method. 24% enhancement of the PCE is achieved for the PSC with 2.0% H4abtc comparing with the pure PSC without H4abtc. Further research suggests that the H4abtc can passivate grain boundaries of perovskite film by reacting with the lead cation, therefore leading to good thermal stability and anti-moisture of perovskite films. The paper provides a new method to prepare a stable and efficient PSC by employing a novel Lewis base to passivate grain boundaries and gain high-quality perovskite films.

RETRACTED ARTICLE: Solvent-Free Cyanosilylation of Aldehydes and Anti-cervical Cancer Activity of a Highly Porous Zinc-MOF

A new three-dimensional (3D) zinc(II) metal–organic framework (MOF) {[Zn2(abtc)(H2O)3](DMA)}n bearing the rigid organic ligand 3,3′,5,5′-azobenzene-tetracarboxylic acid (H4abtc) were prepared by reaction of zinc(II) nitrate and H4abtc in a mixed solvent of DMA and water at 80 °C for 3 days. Compared with pristine hydrated 1, the dehydrated 1a exhibits highly efficient catalytic activity for cyanosilylation of carbonyl compounds with a low catalyst loading of 0.1 mol% at room temperature under solvent-free conditions, which due to the open Zn2+ sites as catalytically activated sites played a significant role in the heterogeneous catalytic process. Based on the experimental results, a possible reaction mechanism has also been proposed. Next, the inhibitory effect of compound 1a on Hela cervical cancer cell viability was evaluated by CCK-8 assay, and the percentage of cell cycles was determined in flow cytometry. Besides, the transwell assay also performed to detect the effect of compound 1a on cell migration and invasion.

Acetonitrile sensing property of a microporous Co(II) metal-organic framework based on azobenzenetetracarboxylate ligand

A new Co(II)-MOF [NH2(CH3)2][Co1.5(abtc)]·H2O (1) (H4abtc: 3,3′,5,5′‑azobenzenetetracarboxylic acid) has been solvothermally synthesized and characterized. Complex 1 is a three-dimensional {Co3}-based framework with one-dimensional channels bridged by the μ2-bridging abtc ligand, resulting in a (4, 8)-connected topology. Luminescent studies reveal that complex 1 shows weak emission in solid state at room temperature, but the emission intensities have greatly enhanced in both liquid suspensions and solid state after immersion in acetonitrile solvent.

A microporous metal–organic framework with soc topology for adsorption and separation selectivity of C2H2/CO2

The microporous metal–organic framework [Co3O(H2O)3](ABTC)1.5·(solv)x, (H4ABTC = 3,3′,5,5′-azobenzenetetracarboxylic acid) Co-ABTC, with suitable pore space was synthesized by solvothermal reaction. Co-ABTC shows the spherical pores with a radius of 5.2 × 5.2 A2, taking into account the van der Waals’ force. The specific surface area (BET) is 585.9 m2/g through N2 adsorption at 77 K. The activated Co-ABTCa shows the moderately high separation selectivity for C2H2/CO2 of 4.28 (298 K) at extremely low pressures by utilizing ideal adsorbed solution theory simulation. A new microporous metal–organic framework with optimizing pore space has been realized to exhibit highly selective C2H2/CO2 gas separation property.

Assembly of metal–organic frameworks based on 4-connected 3,3′,5,5′-azobenzenetetracarboxylic acid: structures, magnetic properties, and sensing of Fe3+ ions

Three complexes based on 3,3′,5,5′-azobenzenetetracarboxylic acid were synthesized, showing potential applications in magnetism and excellent sensing properties towards Fe3+.

Microporous metal–organic framework with open Cu2+ functional sites and optimized pore size for C2H2 storage and CH4 purification

A microporous metal–organic framework (MOF), Cu6(ABTC)3(H2O)6·(DMA)7(H2O)12 (Cu-ABTC, H4ABTC = 3,3′,5,5′-azobenzenetetracarboxylic acid) was solvothermal obtained and structurally characterized. The activated Cu-ABTC-a exhibits high BET specific surface area of 2366 m2/g. Due to optimized pore space and open Cu2+ functional sites, Cu-ABTC-a displays high C2H2 storage capacity of 208 cm3 g−1 at 298 K and separation selectivities for equimolar C2H2/CH4 and CO2/CH4 at 298 K, respectively.

Assembly of Zeolite-like Metal-Organic Framework: An Indium-ZMOF Possessing GIS Topology and High CO2 Capture.

An In-ZMOF material, [(CH3)2NH2][In(ABTC)]·3DMF (JLU-MOF52), has been synthesized by using 2,2',5,5'-azobenzenetetracarboxylic acid (H4ABTC) as a linker, which coordinated to four [In(O2C)4]- secondary building units (SBUs) to generate a 3D framework. JLU-MOF52 is constructed by a rare 4 + 4 strategy from 4-connected tetrahedral [In(O2C)4]- SBUs and tetrahedral ligands, which can be described as a (4, 4)-connected and forbidden interpenetrated zeolite-like MOF with GIS topology. The framework exhibits significant advantages in terms of chemical stability. N2 adsorption study of the activated JLU-MOF52 material reveals a Langmuir and a BET surface area is 1302 and 966 m2 g-1, respectively. Furthermore, the adsorption amount of CO2 for JLU-MOF52 is studied under 1 atm, which exhibits the highest CO2 capture ability at 273 K among the ZMOFs materials with GIS topology. These characteristics make JLU-MOF52 promising candidate materials for application in moderating increasing atmospheric CO2 levels.

Controllable and Stable Deformation of a Self-Healing Photo-Responsive Supramolecular Assembly for an Optically Actuated Manipulator Arm

It is highly challenging to achieve an optically deformable polymer with good controllability, stability, and self-healability for fabricating an optically controlled microrobotics. Here, we present a photo-responsive self-healing supramolecular assembly cross-linked by3,3',5,5'-azobenzenetetracarboxylic acid(t-Azo) enabling the controllable and stable deformation. The network (PAA-u) of polyacrylic acid (PAA) grafted with 2-ureido-4[1 H]-pyrimidinone (UPy) is formed via multiple intermolecular hydrogen bonds (H-bonds) between UPy and t-Azo moieties. Molecular H-bonds stabilize the cis-isomer, enables stress transfer at the interface, and also contributes to fast healability. The PAA-u/t-Azo assembly shows a green-light-induced bending deformation, which recovers its shape under the irradiation of UV light. On the basis of this controllable and reversible deformation, the PAA-u/t-Azo "hand" realizes reversible light-driven grabbing and releasing of an object by optimizing bending and recovery. The assembly also shows a fast and excellent self-healing performance irradiated by green light during deformation. The multiple-H-bonding-cross-linked assembly with stable deformation and fast self-healability can be used for the development of a multitude of advanced microrobotics.