Heterometallic MOFs Research Articles

Ultrahigh stable heterometallic InCo-organic framework for efficiently catalyzing cycloaddition of CO2 with epoxides and Knoevenagel condensation

Due to versatile applications and fascinating topologies of heterometallic MOFs, developing new functional frameworks is of great significance and a great challenge. Inspired by this, we target to assemble rarely reported d-p heterometallic MOFs by using 4,4′-(4-(4-carboxyphenyl)pyridine-2,6-diyl)diisophthalic acid (H5CPPDA) as the organic linker, whose N and O donors have different affinities to d and p ions according to the soft-hard theory. Herein, a highly robust nanochannel-based InCo-organic framework of [InCo(CPPDA)(H2O)]·4DMF·6H2O}n (NUC-85) was successfully achieved under the acidic solvothermal condition. In the host framework of NUC-85, the ligand of CPPDA5− utilizes its five deprotonated carboxyl groups with three kinds of coordination modes (μ1-η1:η1, μ2-η1:η1 and μ3-η2:η1) as well as pyridine to combine In3+ and Co2+ ions into scarcely reported one-dimensional chains of [InCo(COO)5(H2O)]n, six of which are further arranged into hexagonal nano-channels (aperature ca. 14.5 Å). After thermal activation, the inner surface of channels in NUC-85a is functionalized by open metal sites of octa-coordinated In3+ and penta-coordinated Co2+ ions. Performed experiments prove that NUC-85a is an excellent heterogeneous catalyst for the cycloaddition of CO2 with epoxides under the mild conditions. Moreover, the Knoevenagel condensation with benzaldehyde and malononitrile as substrates can be efficiently catalyzed by NUC-85a. In the above two kinds of organic reactions, NUC-85a displays the satisfied chemical stability, high selectivity and multiple repeatability. This research demonstrates that nanostructure-based heterometallic MOFs have a bright future as a catalyst for Lewis acid/base supported organic reactions because of their congenital advantages such as sufficient active sites, high stability and convenient recyclability.

Luminescent and magnetic [TbEu] 2D metal-organic frameworks.

We present the synthesis, through a simple, microwave-assisted method, of lanthanoid-based 2D metal-organic frameworks (MOFs) of general formula [LnxLn'1-x(MeCOO)(PhCOO)2], including homonuclear compounds (x = 1), LnEu, Tb, and heterometallic compounds, [TbEu]. The crystalline material is formed by neutral nanosheets held together by van der Waals interactions, which can be easily exfoliated by sonication. Photoluminescent emission in the visible range was observed for all of the synthesized 2D MOF compounds via excitation of the ligand, showing benzoates are efficient antenna ligands. Efficient energy transfer from Tb → Eu was observed in the heterometallic [TbEu] compounds, which could potentially perform as luminescent thermometers. Inks containing nanosheets of 2D MOFs exfoliated in solution were prepared, and luminescent prints of Tb and Eu 2D MOFs on paper were made to show the possible application for anticounterfeiting. Frequency-dependent ac susceptibility results show the occurrence of slow magnetic relaxation in [TbEu] compounds through direct relaxation mechanisms, affected by bottleneck effect. A slowing down of the relaxation time is observed as the Eu/Tb ratio increases.

Inside Cover: Selective Implantation of Diamines for Cooperative Catalysis in Isoreticular Heterometallic Titanium–Organic Frameworks (Angew. Chem. Int. Ed. 21/2021)

A selective grafting route for heterometallic MOFs is described by Carlos Martí-Gastaldo and co-workers in their Research Article on page 11868. The different chemistry of Ti(IV) and Ca(II) sites is used to direct selective coordination of amines to the latter. This enables the combination of Lewis acid titanium centers and available -NH2 sites in two sizeable pores for cooperative cycloaddition of CO2 to epoxides at room temperature and atmospheric pressure.

Heterometallic Actinide‐Containing Photoresponsive Metal‐Organic Frameworks: Dynamic and Static Tuning of Electronic Properties

AbstractAcquiring fundamental knowledge of properties of actinide‐based materials is a necessary step to create new possibilities for addressing the current challenges in the nuclear energy and nuclear waste sectors. In this report, we established a photophysics–electronics correlation for actinide‐containing metal‐organic frameworks (An‐MOFs) as a function of excitation wavelength, for the first time. A stepwise approach for dynamically modulating electronic properties was applied for the first time towards actinide‐based heterometallic MOFs through integration of photochromic linkers. Optical cycling, modeling of density of states near the Fermi edge, conductivity measurements, and photoisomerization kinetics were employed to shed light on the process of tailoring optoelectronic properties of An‐MOFs. Furthermore, the first photochromic MOF‐based field‐effect transistor, in which the field‐effect response could be changed through light exposure, was constructed. As a demonstration, the change in current upon light exposure was sufficient to operate a two‐LED fail‐safe indicator circuit.

Heterometallic Actinide-Containing Photoresponsive Metal-Organic Frameworks: Dynamic and Static Tuning of Electronic Properties.

Acquiring fundamental knowledge of properties of actinide-based materials is a necessary step to create new possibilities for addressing the current challenges in the nuclear energy and nuclear waste sectors. In this report, we established a photophysics-electronics correlation for actinide-containing metal-organic frameworks (An-MOFs) as a function of excitation wavelength, for the first time. A stepwise approach for dynamically modulating electronic properties was applied for the first time towards actinide-based heterometallic MOFs through integration of photochromic linkers. Optical cycling, modeling of density of states near the Fermi edge, conductivity measurements, and photoisomerization kinetics were employed to shed light on the process of tailoring optoelectronic properties of An-MOFs. Furthermore, the first photochromic MOF-based field-effect transistor, in which the field-effect response could be changed through light exposure, was constructed. As a demonstration, the change in current upon light exposure was sufficient to operate a two-LED fail-safe indicator circuit.

Influence of Substituents in Terephthalate Linker on the Structure of MOFs Obtained from Presynthesized Heterometallic Complex

The synthesis of new porous materials with desired properties is a challenging task. It becomes especially difficult if you need to combine several metals in one framework to obtain a heterometallic node. The use of presynthesized complexes for obtaining of new heterometallic metal–organic frameworks could be essential to solve the problem of tailored synthesis. In our study we use presynthesized heterometallic pivalate complex [Li2Zn2(piv)6(py)2] to obtain new MOFs with heterometallic core as a node of the framework. We are managed to obtain four new heterometallic MOFs: [H2N(CH3)2]2[Li2Zn2(bdc)4]·CH3CN·DMF (1), [Li2Zn2(H2Br2-bdc)(Br2-bdc)3]·2DMF (2), [H2N(CH3)2][LiZn2(ndc)3]·CH3CN (3) and [{Li2Zn2(dmf)(py)2}{LiZn(dmf)2}2 (NO2-bdc)6]·5DMF (4). Moreover three of them contain starting tetranuclear core {Li2Zn2} and saves its geometry. We also demonstrate the influence of substituent in terephthalate ring on preservation of tetranuclear core. For compound 1 it was shown that luminescence of the framework could be quenched when nitrobenzene is included in the pores.

Heterometallic MOFs constructed from thiophene and furandicarboxylate ligands for heavy metal luminescence sensing.

Rational design of a series of new heterometallic MOFs was carried out by the judicious choice of the corresponding synthesis conditions and ligand geometry. Three heterometallic MOFs (H2NMe2)[LiZn(dmf)(tdc)2]·DMF·H2O (1), [{LiZn}2Li2Zn2(dmf)6(tdc)6]·6DMF·H2O (2) and [Li2Zn2(dmf)2(fdc)3]·2DMF·2H2O (3) were obtained on the basis of the pre-synthesized pivalate complex [Li2Zn2(py)2(piv)6]. The angle between carboxylic groups greatly affects the possibility of retaining the initial tetranuclear node in the structure of the obtained MOFs. Compound 3 demonstrates permanent porosity with a calculated BET surface area value of 287 m2 g-1. Compounds 2 and 3 are capable of heavy metal sorption from their nitrate solution, and a significant flare-up of the luminescence of the obtained inclusion compounds is observed, where the quantum yield of luminescence increases by an order of magnitude in the case of cadmium inclusion.

Varied proton conductivity and photoreduction CO2 performance of isostructural heterometallic cluster based metal–organic frameworks

A family of isostructural heterometallic MOFs based on Fe2M clusters serve as potential proton conductors and photocatalysts for CO2 photoreduction.

Heterometallic metal-organic frameworks: two-step syntheses, structures and catalytic for imine synthesis

Herein, two heterometallic metal organic frameworks were reported by two-step synthesis strategies. By employing the neutral {Fe 2 III ZnO(O 2 CCCl 3 ) 6 (CH 3 OH) 3 } ( 1 ) metalloligand precursor, two new heterometallic{Fe 2 II / III -Zn} cluster-based coordination polymers, namely, {[Fe II / III 2 Zn(BDC) 4 ]•NH 2 (Me) 2 } n ( MOF2 ) and {[Fe II / III 2 Zn(μ 3 -O) (BTC) 2 (CH 3 CH 2 CH 2 OH)]·NH 2 (Me) 2 } n ( MOF3 ), were synthesized and structurally characterized. MOF2 exhibited 8-connected 3D bcg topological net based on Fe II / III 2 Zn(OCO) 6 heterometallic unit. MOF3 showed 3D framework based on Fe II / III 2 Zn(μ 3 -O) (OCO) 4 trinuclear unit with binodal (3,6)-connected scu/p topology, and possessed two kinds of 1D hydrophobic and hydrophilic open channel along the c axis. Interestingly, both Fe II and Fe III ions with 1:1 ratio were observed in the trinuclear unit and confirmed by bond valence sum (BVS), X-ray photoelectron spectroscopy (XPS) and Mössbauer spectroscopy studies. The transformation was accompanied by the dissolution, self-reduction of Fe III to Fe II and the cleavage/regeneraion of coordination bonds. Meanwhile, the heterogeneous catalytic effects for one-pot synthesis of imine from amine and alcohols under solvent-free conditions were also studied. Two Fe II /Fe III mixed valence heterometallic MOFs constructed from neutral {Fe 2 III ZnO(O 2 CCCl 3 ) 6 (CH 3 OH) 3 } metalligand precursor exhibit good catalytic activities in one-pot synthesis of imine from amine and alcohol under solvent-free condition. • Two Fe II /Fe III mixed valence heterometallic MOFs were constructed from {Fe 2 III ZnO(O 2 CCCl 3 ) 6 (CH 3 OH) 3 } metalloligand precursor. • MOF 3 contained two kinds of 1D hydrophobic and hydrophilic open channels. • MOF 3 was a good heterogeneous catalyst for the synthesis of imine under solvent-free condition

A Heterometallic MOF based on Monofunctional Linker by “One‐pot” Solvothermal Method for Highly Selective Gas Adsorption

Heterometallic MOFs, as an important branch of MOF materials, open up a new way to design and synthesize innovative MOF materials. Hence, it has positive significance for the development of MOF materials. By utilizing monofunctional linker CBDA [5,5'‐(carbonylbis(azanediyl))‐diisophthalic acid], a heterometallic MOF In/Gd‐CBDA was obtained under “one‐pot“ solvothermal method. The three‐dimensional framework exhibits (3,4,6)‐connected network belonging to a new topology. In addition, the synthetic conditions that affect the growth of crystal have been studied in detail. Numerous experiments led to the finding that the type and composition of solvents are very important for inducing the recognition of carboxylic acid groups at different positions coordination to diverse metals. Furthermore, the mechanism of this kind of heterometallic MOFs assembled by monofunctional linker under “one‐pot” solvothermal method has been clarified, which is mainly related to the steric hindrance of functional groups and the properties of heterometals. Based on ideal adsorbed solution theory (IAST), In/Gd‐CBDA shows the efficient selective gas adsorption, especially for equimolar mixtures of CO2/CH4 (13) and C3H8/CH4 (321). This work of heterometallic MOF material assembled by monofunctional linker under “one‐pot” solvothermal method provides a new platform for the development of MOF materials in terms of enriching the topological family and broadening possibilities in advanced applications.

Heterometallic Titanium–Organic Frameworks by Metal-Induced Dynamic Topological Transformations

Reticular chemistry has boosted the design of thousands of metal and covalent organic frameworks for unlimited chemical compositions, structures, and sizable porosities. The ability to generate porous materials at will on the basis of geometrical design concepts is responsible for the rapid growth of the field and the increasing number of applications derived. Despite their promising features, the synthesis of targeted homo- and heterometallic titanium-organic frameworks amenable to these principles is relentlessly limited by the high reactivity of this metal in solution that impedes the controlled assembly of titanium molecular clusters. We describe an unprecedented methodology for the synthesis of heterometallic titanium frameworks by metal-exchange reactions of MOF crystals at temperatures below those conventionally used in solvothermal synthesis. The combination of hard (titanium) and soft (calcium) metals in the heterometallic nodes of MUV-10(Ca) enables controlled metal exchange in soft positions for the generation of heterometallic secondary building units (SBUs) with variable nuclearity, controlled by the metal incorporated. The structural information encoded in the newly formed SBUs drives an MOF-to-MOF conversion into bipartite nets compatible with the connectivity of the organic linker originally present in the crystal. Our simulations show that this transformation has a thermodynamic origin and is controlled by the terminations of the (111) surfaces of the crystal. The reaction of MUV-10(Ca) with first-row transition metals permits the production of crystals of MUV-101(Fe,Co,Ni,Zn) and MUV-102(Cu), heterometallic titanium MOFs isostructural with archetypical solids such as MIL-100 and HKUST. In comparison to de novo synthesis, this metal-induced topological transformation provides control over the formation of hierarchical micro-/mesopore structures at different reaction times and enables the formation of heterometallic titanium MOFs not accessible under solvothermal conditions at high temperature, thus opening the door for the isolation of additional titanium heterometallic phases not linked exclusively to trimesate linkers.

Reversible Dynamic Structural Transformation between 3D and 1D Cd–Co Heterometallic MOFs Showing Switchable Spin-Canted Antiferromagnetism

Two Cd-Co heterometallic frameworks based on the ligand methylenesuccinate acid (H2MSA), three-dimensional (3D) [CdCo6(MSA)6(μ3-OH)2(H2O)2]·H2O (1) and one-dimensional (1D) [CdCo(MSA)2(H2O)5]·3H2O ...

Solution-processable Yb/Er 2D-layered metallorganic frameworks with high NIR-emission quantum yields

2D-layered Yb/Er homo- and heterometallic MOFs with the chlorocyananilate linker display long-lived NIR emission and high total quantum yields upon ligand excitation over the whole UV-visible spectrum.

Rational synthesis and dimensionality tuning of MOFs from preorganized heterometallic molecular complexes.

Rational synthesis of a series of new heterometallic MOFs was carried out by the judicious choice of the corresponding pivalate complexes [Li2M2(piv)6(py)2] (M = Zn2+, Co2+, piv- = pivalate anion and py = pyridine) as a source of secondary building units, {LiM(O2CR)3} and an organic tricarboxylate linker as a node defining the dimensionality of the framework by the orientation of the carboxylic group in or out of the central aromatic ring plane. Thus the trimesate (btc3-) linker results in 3D srs topology frameworks with intersecting systems or isolated channels, and 1,3,5-benzenetribenzoate (btb3-) results in layered hcb isostructural compounds additionally stabilized with H-π interactions between the layers. The layered compounds demonstrate a permanent porosity with a BET surface area of up to 688 m2·g-1 with the possibility of selective gas adsorption (CO2 over N2 and CH4). Zn-Based coordination polymers show notable color changes and drastic (up to 30 times) quenching of luminescence upon inclusion of different nitroaromatics.

A new type of composite MOFs based on high-valent Sb(v)-based units and cuprous-halide clusters

An unusual high-valent Sb(v)-based unit [SbL2]- (L = 2-(hydroxymethyl)-2-(pyridin-4-yl)-1,3-propanediol) was developed for the first time to combine with various cuprous-halide clusters for the construction of a brand-new class of heterometallic MOFs. This work not only promotes the limited development of Sb-based MOFs, but also provides a practical strategy for developing new types of composite materials.

A heterometallic microporous MOFs with two types of intrinsic secondary building units for selective gas separation and luminescence property

Based on the Modified Bifunctional Method, a new heterometallic metal organic frameworks (InOF-17) with the coexistence of mononuclear In(CO2)4 SBUs and trinucleate Zn3(μ3-OH)(CO2)6 SBUs has been successfully synthesized and structurally characterized. InOF-17 shows a three-dimensional heterometallic microporous framework with interconnected channels assembled by two types of SBUs. In addition, the selective gas separation and the luminescence property of InOF-17 were investigated.

Robust heterometallic MOF catalysts for the cyanosilylation of aldehydes

Zn2+/Cu2+ ions are doped into a Mn2+ based frail MOF to form robust heterometallic MOFs catalysts for the cyanosilylation of aldehydes.

Phonon, optical and luminescent properties of novel heterometallic frameworks of [(NH4)(H2O)][CrIIIMII(HCOO)6] (MII=Mn, Zn, Co, Ni)

We report synthesis of four novel heterometallic MOFs, [(NH4)(H2O)][CrIIIMII(HCOO)6] with MII = Zn (NH4CrZn), Co (NH4CrCo), Mn (NH4CrMn) and Ni (NH4CrNi). X-ray diffraction shows that NH4CrZn crystallizes in the trigonal structure (space group P3¯1c) with ordered Cr3+ and Zn2+ centers while NH4CrCo, NH4CrMn and NH4CrNi crystallize in the hexagonal system with chiral space group of P6322 and statistical occupation of the same sites by Cr3+ and M2+ ions. Raman and IR data confirm presence of water molecules and different confinement of the ammonium cations in the cavities of chiral and niccolite type metal formate frameworks. Optical studies show that Cr3+ ions in NH4CrZn and NH4CrMn are located at sites of strong crystal field with the Dq/B values of 2.54 and 2.47, respectively. Luminescence studies show that these compounds exhibit efficient Cr3+-based emission with the decay time of 8.1 μs (0.44 ms) at 295 K (10 K) for NH4CrMn and 8.3 μs (0.78 ms) for NH4CrZn.

Series of chiral interpenetrating 3d–4f heterometallic MOFs: Luminescent sensors and magnetic properties

Series of chiral 3d-4f heterometallic MOFs based on a multidentate terpyridyl carboxylic acid ligand have been synthesized under the solvothermal conditions, namely, [LnZnL(CO3)2(H2O)]n (Ln = Eu (1), Gd (2), Dy (3), Ho (4), Er (5), Tm (6), Yb (7), Lu (8)) (HL = 4′-(4-carboxyphenyl)−2,2′:6′,2″-terpyridine). Compounds 1–8 were structurally characterized by the elemental analyses, infrared spectra, and single crystal X-ray diffractions. Compounds 1–8 exhibit the chiral interpenetrating 3D frameworks. Interestingly, 1 can serve as the luminescent sensor to detect nitrobenzene molecules with high sensitivity. The investigations on CD spectra of single crystals clearly assigned the Cotton effect, indicating that there exist two chiral enantiomers of 1–8 in the course of crystallization. The magnetic properties of 2 and 7 were exploited, respectively.

Vibrational and magnetic properties of [C2H5NH3][FeIIIMII(HCOO)6] (M = Mn, Ni) and [C2H5NH3][CrIIIMnII(HCOO)6] framework compounds

We report synthesis, X-ray diffraction, magnetic and vibrational studies of three novel heterometallic MOFs, [C2H5NH3][FeIIIMII(HCOO)6] with M=Ni (EtFeNi) and Mn (EtFeMn) as well as [C2H5NH3][CrIIIMnII(HCOO)6] (EtCrMn) crystallizing in the niccolite type architecture (space group P3¯1c) with disordered ethylammonium (EtA+) cations located in the large cavities. Magnetic studies show that EtFeNi and EtFeMn exhibit ferromagnetic order below 43 and 38K, respectively, whereas EtCrMn remains paramagnetic at least down to 2K. Analysis of the Raman and IR data allowed us to propose assignment of the observed bands to the respective internal and lattice modes. These data give also evidence for weaker amine-cavity interactions compared to the perovskite analogues and show that this difference has significant effect on structure of the EtA+ cation. We also report that synthesis of Mg-analogues resulted in formation of ethylammonium magnesium formate with partially substituted Mg2+ (by Cr3+ or Fe3+) and EtA+ cations (by HCOOH molecules). These mixed-metal compounds have most likely the same R3¯symmetry as the high-temperature phase of undoped perovskite-type [C2H5NH3][Mg(HCOO)3].