Heterobimetallic Metal Organic Framework Research Articles

MOF-templated CuO and Mn[sbnd]CuO/Cu2O composites as electrocatalyst in oxygen evolution

Considering the great need for the development of new electrocatalysts for oxygen evolution reaction (OER), this work reports the synthesis and characterization of four new copper-based electrocatalysts derived from metal–organic frameworks (MOFs). Homometallic (CuIDA, [Cu(IDA)(H2O)2]n IDA= iminodiacetate) and heterobimetallic [Cu0.902Mn0.096(IDA)(H2O)2]n, [Cu0.703Mn0.297(IDA)(H2O)2]n and [Cu0.487Mn0.513(IDA)(H2O)2]n MOFs were obtained by precipitation method and characterized by X-ray diffraction (XRD) with Rietveld refinement, infrared spectroscopy (FT-IR) and thermogravimetric (TGA). The calcination of CuIDA and heterobimetallic MOFs under air atmosphere led to the formation of CuO and CuO/Cu2O/Mn-x (x = 10 %, 20 % and 50 % of Mn) electrocatalyst, respectively. These materials were characterized by XRD, FT-IR, Raman spectroscopy, UV–vis spectroscopy and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), confirming the chemical composition and crystal structure. Copper oxide-based materials were applied as electrocatalyst for OER in alkaline medium, with overpotential of 359 mV (CuO), 355 mV (CuO/Cu2O/Mn10), 360 mV (CuO/Cu2O/Mn30) and 355 mV (CuO/Cu2O/Mn50) to record a current density of J = 10 mA cm−2. Tafel slope values indicate the adsorption of intermediate species as the rate-determining step for all electrocatalysts. These results are similar or superior to those found in the literature so far.

The enhancement of heterobimetallic MOFs on the pyrolysis and laser ignition of FOX-7

The hydrothermal approach had been used to synthesize two new heterobimetallic Metal Organic Frameworks (MOFs), Ba4Pb4(CH3CO2)8[(CH6CO2)4Pb](CH3CO2)4 (PbBa-MOF) and Ba2Ni(CO2H)6(OH2)4 (NiBa-MOF), their structure and surface topography were then examined with XRD and SEM. By using the TG-DSC and TG-FTIR-MS methods, the pyrolytic decomposition properties of MOFs and their catalytic activities on the 1,1-diamino-2,2-dintroethene (FOX-7) pyrolysis were investigated. The PbBa-MOF has a single thermal decomposition process with a high thermal decomposition temperature, while NiBa-MOF has a three-stage thermal decomposition process initiated from a lower temperature. Furthermore, the thermolysis peak temperature of the FOX-7/PbBa-MOF and FOX-7/NiBa-MOF mixture has a great decrease by 24.2 °C and 27.4 °C compared with the FOX-7. However, the low pyrolysis peak temperature and the pyrolysis activation energy (Ea) are almost unchanged. The selective high temperature catalytic effect of the MOFs on FOX-7 results from the activation of -NH2 in the high temperature pyrolytic decomposition of FOX-7 by the metallic ions of the MOFs. This thermal catalytic property indicates that MOFs can promote the pyrolytic decomposition of FOX-7 while ensuring the safety requirements for the compatibility of energetic mixtures in the preparation of propellants. The relationship between the features of pyrolytic decomposition and laser ignition was finally covered and defined. The two MOFs decreased the minimum ignition energy and ignition delay time of the FOX-7. Novel MOFs combustion catalyst may strengthen ignition and combustion features of the high-energy and low-sensitivity solid propellants containing FOX-7.

Copper(II) pseudoatrane appended heterobimetallic 2D‐MOF: A multi‐functional material with catalytic and sensing properties

A maiden two‐dimensional atrane‐based heterobimetallic MOF (2) was constructed employing a novel tripodal ligand N{CH2COOH}2{CH2(2‐t‐Bu‐4‐CH3‐C6H2‐OH)} (1). Single‐crystal X‐ray diffraction depicted the formation of [4.3.3.01,5] pseudoatrane cage in which copper(II) ions attained trigonal bipyramidal geometry. Besides, the co‐existing sodium(I) ions acquired a pentagonal bipyramidal geometry produced by methanol molecules and free carboxylate sites of the ligand. This compound is the first of its kind where the sequential binding of copper(II) pseudoatrane cage and hepta‐coordinated sodium ion generated a heterobimetallic metal–organic framework with a sheet‐like structure. The TEM and SEM images of the MOF having stability up to 250°C revealed the formation of spherical structures (~78 nm) with flower‐like morphology. The heterobimetallic 2D‐MOF was proved to be a multifunctional material as it successfully catalysed Friedel–Craft's alkylation of Indole with beta‐nitrostyrene as well as utilised for the efficient detection of toxic brominated flame retardants through spectrophotometric and colorimetric studies. Remarkably, the best catalysis results were seen using DCM as a solvent, and the alkylation product obtained from the reaction of 2‐methylindole with 2‐Br‐β‐nitrostyrene showed an extraordinary yield of 98%. Besides, the 2D‐MOF showed a selective response with pentabromophenol, and tetrabromophthalic anhydride with quenching in peak on the addition of TBPA while shifting of the peak was observed from 457 to 402 nm with PBP. The practical application of the MOF was explored by its successful incorporation into portable silica strips for on‐the‐spot detection of BFRs.

Synthesis of novel heterobimetallic MOFs and its effect on thermolysis and laser ignition of TKX-50

Two novel heterobimetallic metal-organic frameworks (MOFs), Ba4Pb4(CH3CO2)8[(CH6CO2)4Pb](CH3CO2)4 (PbBa-MOFs) and Ba2Ni(CO2H)6(OH2)4 (NiBa-MOFs), were prepared via the solvothermal method, and their structures were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The pyrolysis behavior of the two MOFs and their catalytic performances on the dihydroxylammonium-5,5’-bistetrazole-1,1’-diolate (TKX-50) pyrolysis were studied by thermogravimetric-differential scanning calorimetry (TG-DSC) and thermogravimetric-fourier transform infrared spectroscopy-mass spectrum (TG-FTIR-MS) methods. Compare with the pure TKX-50, the pyrolysis peak temperature and apparent activation energy (Ea) of the TKX-50/PbBa-MOFs mixture were decreased by 3.2°C and 13.47 kJ‧mol−1 respectively. The Ea of TKX-50/NiBa-MOFs was decreased by 9.35 kJ‧mol−1. And the second pyrolysis peak disappeared in the DSC curves of TKX-50 after the addition of the two MOFs, due to that the products from MOFs pyrolysis suppress the chemical reaction pathway on the production of 5,5′-bis (2-hydroxytetrazole) (ABTOX) and accelerate the direct decomposition of 1,1’-bistetrazole diol (BTO). This resulted in the percentage of H2O decreased greatly and the percentage of NO/CH2O, CO2/N2O, NH2+/O• and NH3/OH increased during the pyrolysis of TKX-50. Finally, the relation between the pyrolysis and ignition characteristics was discussed and described. The two MOFs reduced the ignition delay time of the TKX-50 at the high power density region, and the flame becomes more luminous due to the formation of metal oxides and active free radical.

Two novel heterobimetallic metal-organic frameworks for the enhanced catalytic thermolysis and laser ignition of CL-20

The study of multiple complex catalytic mechanisms is currently one of the great scientific issues for the application of high-energy solid propellants. Two novel heterobimetallic metal-organic frameworks (MOFs), Ba4Pb4(CH3CO2)8 [(CH6CO2)4Pb](CH3CO2)4 (PbBa-MOF) and Ba2Ni(CO2H)6(OH2)4 (NiBa-MOF), were prepared via the solvothermal method, and their structures and composition were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR) techniques and N2 adsorption/desorption experiment. The thermal decomposition characteristics of the two MOFs and their catalytic performances on the hexanitro hexaazaisowurtzitane (CL-20) thermolysis were also studied by differential scanning calorimetr (DSC) and thermogravimetric-fourier transform infrared spectroscopy-mass spectrum (TG-FTIR-MS) methods. The results showed that the NiBa-MOF presented a lower initial decomposition temperature than the PbBa-MOF, and the difference of the MOFs structures affected the starting point of thermal decomposition. Compared with the pure CL-20, the thermolysis peak temperature and apparent activation energy (Ea) of the CL-20/PbBa-MOF mixture were decreased by 2.2 °C and 23.76 kJ‧mol−1, respectively. The Ea of CL-20/NiBa-MOF mixture was lower and 42.01 kJ‧mol−1, indicating the better catalytic activity of NiBa-MOF. The thermolysis catalytic mechanisms were studied by analyzing the transformation of gas products during the pyrolysis of mixtures. The effect of these two MOFs on the CL-20 thermolysis is primarily owing to the strong attraction of metal cations to electronics, bimetallic synergistic catalysis, and the release of active free radicals. Furthermore, the laser ignition and flame propagation features showed that these two MOFs reduced the minimum ignition power density and ignition delay time of the CL-20, and the flame becomes brighter and more luminous. The influence of the two MOFs on the flame bright spot of CL-20 based mixtures was described.

Syntheses, structures, luminescence and CO2 gas adsorption properties of four three-dimensional heterobimetallic metal–organic frameworks

A new pyridyl-tricarboxylic acid ligand, 4,4'-(6-carboxypyridine-2,4-diyl)dibenzoic acid (H3L), was used to construct one zero-dimensional (0D) complex, [Co(H2L)2(H2O)2]•2H2O (1), and four isostructural three-dimensional (3D) heterobimetallic metal-organic frameworks (MOFs), [MNa(L)(H2O)]n•solvents (M ​= ​Co (2), Ni (3), Cu (4) and Zn (5)). The dimensionality ranging from 0D complex (1) to 3D frameworks (2–5) should be ascribed to various solvents (from MeCN to DMA/DMF) or whether presence of Na+ cation or not. Interestingly, isostructural 3D heterobimetallic MOFs 2–5 possess rhombic voids and reveal CO2 gas adsorption features. Because heterobimetallic MOFs 2 and 5 possess higher framework stability than 3 and 4, 2 and 5 exhibit higher CO2 adsorption capacities at 273 ​K. Furthermore, photoluminescence properties of 1–5 have also been investigated. The present work provides a promising approach to design and construct heterobimetallic MOFs containing alkali-metal cations, and then to tune CO2 adsorption properties.

Metal organic framework for sensing toxic metal ions in water

Abstract Hetero bimetallic metal organic framework (MOF) of zirconium, and copper has been synthesized using benzene-1,4-dicarboxylic acid (BDC) as the linker by solvothermal synthesis. The MOF has been characterized using FT-IR, powder XRD, FE-SEM, EDAX, TEM, TGA, UV and PL analysis. Also the sensing capability of the MOF has been investigated using different concentrations of toxic metal ions like lead (II) and chromium (VI).

Rational Design of a N,S Co-Doped Supermicroporous CoFe-Organic Framework Platform for Water Oxidation.

It remains a challenge to rational design of a new metal-organic framework (MOF) as highly efficient direct electrocatalysts for the oxygen evolution reaction (OER). Herein, we developed a simple and effective method to explore a new pillared-layered MOF with syringic acid as a promising OER electrocatalyst. The isostructural mono-, heterobimetallic MOF and N,S co-doped MOF by mixing thiourea were quickly synthesized in a high yield under solvothermal condition. Moreover, the optimized N,S co-doped MOF exhibits the lowest overpotential of 254 mV at 10 mA cm-2 on a glass carbon electrode and a small Tafel slope of 50 mV dec-1 , especially, this catalyst also possesses long-term electrochemical durability for at least 16 h. According to the characterization, the incorporation of N and S atoms into this heterobimetallic CoFe-based MOF could modify its pore structure, tune the electronic structure, accordingly, improve the mass and electron transportation, and facilitate the formation of active species, as a consequence, the improved activity of this new N,S co-doped MOF for OER should be mainly be ascribed to higher electrochemical activation toward the active species via in situ surface modification during the OER process.

Atomically Precise Crystalline Materials Based on Kinetically Inert Metal Ions via Reticular Mechanopolymerization

AbstractAtomistic control of the coordination environment of lattice ions and the distribution of metal sites within crystalline mixed‐metal coordination polymers remain significant synthetic challenges. Herein is reported the mechanochemical synthesis of a reticular family of crystalline heterobimetallic metal–organic frameworks (MOFs) is now achieved by polymerization of molecular Ru2[II,III] complexes, featuring unprotected carboxylic acid substituents, with Cu(OAc)2. The resulting crystalline heterobimetallic MOFs are solid solutions of Ru2 and Cu2 sites housed within [M3L2] phases. The developed mechanochemical strategy is modular and allows for systematic control of the primary coordination sphere of the Ru2 sites within an isoreticular family of materials. This strategy is anticipated to provide a rational approach to atomically precise mixed‐metal materials.

Atomically Precise Crystalline Materials Based on Kinetically Inert Metal Ions via Reticular Mechanopolymerization.

Atomistic control of the coordination environment of lattice ions and the distribution of metal sites within crystalline mixed-metal coordination polymers remain significant synthetic challenges. Herein is reported the mechanochemical synthesis of a reticular family of crystalline heterobimetallic metal-organic frameworks (MOFs) is now achieved by polymerization of molecular Ru2 [II,III] complexes, featuring unprotected carboxylic acid substituents, with Cu(OAc)2 . The resulting crystalline heterobimetallic MOFs are solid solutions of Ru2 and Cu2 sites housed within [M3 L2 ] phases. The developed mechanochemical strategy is modular and allows for systematic control of the primary coordination sphere of the Ru2 sites within an isoreticular family of materials. This strategy is anticipated to provide a rational approach to atomically precise mixed-metal materials.

One-Pot Synthesis of Heterobimetallic Metal-Organic Frameworks (MOFs) for Multifunctional Catalysis.

A one-pot synthesis of bimetallic metal-organic frameworks (Co/Fe-MOFs) was achieved by treating stoichiometric amounts of Fe and Co salts with 2-aminoterephthalic acid (NH2 -BDC). Monometallic Fe (catalyst A) and Co (catalyst F) were also prepared along with mixed-metal Fe/Co catalysts (B-E) by changing the Fe/Co ratio. For mixed-metal catalysts (B-E) SEM energy-dispersive X-ray (EDX) analysis confirmed the incorporation of both Fe and Co in the catalysts. However, a spindle-shaped morphology, typically known for the Fe-MIL-88B structure and confirmed by PXRD analysis, was only observed for catalysts A-D. To test the catalytic potential of mixed-metal MOFs, reduction of nitroarenes was selected as a benchmark reaction. Incorporation of Co enhanced the activity of the catalysts compared with the parent NH2 -BDC-Fe catalyst. These MOFs were also tested as electrocatalysts for the oxygen evolution reaction (OER) and the best activity was exhibited by mixed-metal Fe/Co-MOF (Fe/Co batch ratio=1). The catalyst provided a current density of 10 mA cm-2 at 410 mV overpotential, which is comparable to the benchmark OER catalyst (i.e., RuO2 ). Moreover, it showed long-term stability in 1 m KOH. In a third catalytic test, dehydrogenation of sodium borohydride showed high activity (turnover frequency=87 min-1 ) and hydrogen generation rate (67 L min-1 g-1 catalyst). This is the first example of the synthesis of bimetallic MOFs as multifunctional catalysts particularly for catalytic reduction of nitroarenes and dehydrogenation reactions.

Highly Cuboid-Shaped Heterobimetallic Metal-Organic Frameworks Derived from Porous Co/ZnO/C Microrods with Improved Electromagnetic Wave Absorption Capabilities.

Metal-organic framework (MOF)-derived porous metal/C composites have drawn considerable attention from the microwave absorption field owing to their large pore volumes and surface areas. Exploring single-MOF-derived materials with high intensity and broadband absorption is largely needed but remains a challenge. Here, porous Co/ZnO/C (CZC) microrods were fabricated easily from cuboid-shaped heterobimetallic MOFs. CZC provides an efficient platform for integrating different semiconductors (ZnO), magnetic metal (Co), and carbon sources into one particle, which enhances the electromagnetic (EM) wave-absorbing ability. The carbonization temperature which is critical for EM parameters was studied in detail. CZC annealed at 700 °C outperformed those obtained at 600 or 800 °C in terms of microwave wave-absorbing properties. The reflection loss (RL) was optimized to -52.6 (or -20.6) dB at 12.1 (or 14.8) GHz with an effective bandwidth (RL ≤ -10 dB) of 4.9 (or 5.8) GHz at the coating thickness of 3.0 (or 2.5) mm. Such enhancement of EM wave-absorbing capabilities is ascribed to the well-built porous structure, dielectric loss, and magnetic loss. This work offers a new way to prepare porous magnetic metal/C composites with excellent microwave-absorbing properties starting from heterobimetallic MOFs.

A heterobimetallic metal-organic framework as a "turn-on" sensor toward DMF.

A non-luminescent 3d-4f heterobimetallic CuEu organic framework (NBU-8) was designedly synthesized with Cu2+ ions as a fluorescence quencher. NBU-8 as a sensor realized selective light recovery with a "turn-on" luminescence response toward N,N'-dimethylformamide (DMF) even in the presence of other amide molecules.

Heterobimetallic metal–organic framework nanocages as highly efficient catalysts for CO2conversion under mild conditions

It is of critical importance to design and fabricate highly active and stable catalysts for CO2conversion.

Porous ZnO/NiO Microspherical Structures Prepared by Thermolysis of Heterobimetallic Metal-Organic Framework as Supercapacitor Electrodes

Porous ZnO/NiO Microspherical Structures Prepared by Thermolysis of Heterobimetallic Metal-Organic Framework as Supercapacitor Electrodes

Novel hybrid transition metal complexes of diaquabis(acetylacetonato‐κ2o,o′)[nickel(II)/zinc (II)] as solid metal–organic precursors: Synthesis, properties and magnetic response

A series of hybrid hetero bimetallic metal–organic frameworks, as solid metal–organic precursors, have been prepared via a conventional hydrothermal method. Herein, we report a facile approach for the synthesis of novel crystalline organic–inorganic hybrid compounds of diaquabis(acetylacetonato)[nickel(II)/zinc(II)] in the presence of varying mole ratios of Ni(II)/Zn(II) mixed metal ions. C10H18O6Ni0.7Zn0.3 (N0.7Z0.3AA.2H2O) as an instance of the series has been investigated through detailed characterization. The crystal is composed of N0.7Z0.3AA units and two coordinated water molecules to form a monoclinic structure with space group P21/c. All the solid‐state structures have the metals in octahedral environments forming six‐membered chelate rings. The unit cell dimensions were obtained using single‐crystal X‐ray diffraction. Thermogravimetric analysis reveals that the hybrid compounds can be considered as suitable precursors for the synthesis of oxides via metal–organic chemical vapour deposition. At room temperature, all crystals clearly exhibit paramagnetic behaviour. Besides varying molar ratios of hybrid, the transition point of magnetic behaviour occurs at Ni critical concentration of around 10% in the hybrid. In addition, the magnetic susceptibility increases with increasing Ni content in the compounds.

Rapid and facile ratiometric detection of CO32− based on heterobimetallic metal-organic frameworks (Eu/Pt-MOFs)

A ratiometric fluorescent sensor towards carbonate ions (CO32−) based on a heterobimetallic metal-organic frameworks (Eu/Pt-MOFs) have been synthesized under a facile hydrothermal condition. And then the as-synthesized MOFs are characterized by PXRD, FT-IR, TG, fluorescence spectroscopy and its lifetime (τ). The Eu/Pt-MOFs not only shows dual-emission with a broad band centered at about 560 nm and a characteristic emission of Eu3+ but also have good stability in the aqueous solution, which was further used as a novel fluorescence probe for detecting CO32−. With CO32− addition, the luminescence of Eu3+ is enhanced while the broad band is suppressed significantly. The relative intensity ratio of IEu(614)/ILigand linearly with increasing concentration of CO32− with 0.021 μM detection limit, which much lower than the content of carbonate in accordance with the nutritional and hygienic standards and guidelines for quality certification in children's preferable food. Besides, the robust Eu/Pt-MOFs sustain good stability in aqueous environment, excellent selectivity, fast detection time and applying to different water samples. This work makes the direct, rapid and reliable detection of carbonate ions for practical application possible.

Inverse CeO2/CuO catalysts prepared from heterobimetallic metal–organic framework precursor for preferential CO oxidation in H2-rich stream

Using heterobimetallic metal-organic frameworks (MOFs) as the precursor, a series of inverse CeO2/CuO catalysts, by which cerial nanoparticles were patched on a copper oxide support, were synthesized. These catalysts exhibited excellent catalytic activity and selectivity during preferential CO oxidation in the H2-rich stream. This new approach based on MOFs precursor has two advantages for optimizing the inverse CeO2/CuO catalysts with more copper-ceria interfacial sites: 1) the highly ordered metal-oxygen clusters were completely separated by the organic linkers; and 2) the Ce/Cu configuration can be modulated. We further found that the calcination temperature and heating rate of MOFs are critical for their catalytic activity.

Synthesis of Co1Cu2(BHTC)2 and Its Application in Adsorption Desulfurization

A heterobimetallic metal–organic framework Co1Cu2(BHTC)2 was successfully synthesized based on biphenyl-3,4′, 5-tricarboxylate (H3BHTC). The adsorption desulfurization capability of Co1Cu2(BHTC)2 was investigated in the experiment. Scanning electron microscopy and X-ray diffraction analyses show that Co1Cu2(BHTC)2 possesses a two-dimensional hexagonal morphology and an identical crystallographic structure to that of UMCM-150. Thermogravimetric analysis and Brunauer–Emmett–Teller (BET) analysis indicate that Co1Cu2(BHTC)2 has excellent thermal stability and its BET area can reach up to 2715 m2 g–1. The adsorption desulfurization experiments were conducted based on a in-house built fixed bed at room temperature and atmospheric pressure. The sulfur capacities of the adsorbents were calculated according to breakthrough curves. Compared with UMCM-150 [Cu3(BHTC)2], Co1Cu2(BHTC)2 exhibits different adsorptive desulfurization properties. The experimental results indicate that Cu3(BHTC)2 has a higher sulfur capacity than Co1Cu2(BHTC)2 although the specific surface area of Co1Cu2(BHTC)2 is higher than that of [Cu3(BHTC)2], which can be ascribed to different open metal sites.

Heterobimetallic Metal–Organic Framework as a Precursor to Prepare a Nickel/Nanoporous Carbon Composite Catalyst for 4‐Nitrophenol Reduction

AbstractNickel/nanoporous carbon (Ni/NPC) composites are facilely prepared by direct pyrolysis of nonporous heterobimetallic zinc–nickel–terephthalate frameworks (Zn1−xNixMOF, x≈0–1, MOF=metal–organic framework) at 1223 K in situ. Tailoring the Ni/Zn ratio creates densely populated and small Ni nanocrystals (Ni NCs) while maintaining sufficient porosity and surface area in the final product, which exhibits the largest activity factor (9.2 s−1 g−1) and excellent stability toward 4‐nitrophenol reduction.