Metal-organic Hybrid Materials Research Articles

Charge carrier localised in zero-dimensional (CH3NH3)3Bi2I9 clusters

A metal-organic hybrid perovskite (CH3NH3PbI3) with three-dimensional framework of metal-halide octahedra has been reported as a low-cost, solution-processable absorber for a thin-film solar cell with a power-conversion efficiency over 20%. Low-dimensional layered perovskites with metal halide slabs separated by the insulating organic layers are reported to show higher stability, but the efficiencies of the solar cells are limited by the confinement of excitons. In order to explore the confinement and transport of excitons in zero-dimensional metal–organic hybrid materials, a highly orientated film of (CH3NH3)3Bi2I9 with nanometre-sized core clusters of Bi2I93− surrounded by insulating CH3NH3+ was prepared via solution processing. The (CH3NH3)3Bi2I9 film shows highly anisotropic photoluminescence emission and excitation due to the large proportion of localised excitons coupled with delocalised excitons from intercluster energy transfer. The abrupt increase in photoluminescence quantum yield at excitation energy above twice band gap could indicate a quantum cutting due to the low dimensionality.

Terpyridine-Functionalized NanoSiO2 Multi-Dentate Linkers: Preparation, Characterization and Luminescent Properties of Their Metal–Organic Hybrid Materials

Terpyridine- (TPy-) functionalized silica nanolinkers (nanoSiO2–TPy) have been prepared and used as nanoscale multidentate ligands to coordinate with the transition metal ions (Mn+ = Zn2+, Fe2+, Tb3+ and Eu3+) for producing luminescent metalated organic–inorganic nanoSiO2–TPyM hybrid materials. Thermogravimetric analysis has revealed that the covalently attached organic species in the nanoSiO2–TPy linkers were about 10% in weight. After they were functionalized with the layers of TPy or TPyM, the as-prepared nanoSiO2–TPy linkers and nanoSiO2–TPyM hybrids formed aggregates more easily due to an increase of internanoparticle interactions. The ζ-potential of the nanoSiO2–TPy linkers was about 34.6 mV, which increased to 55 to 60 mV for the nanoSiO2–TPyM hybrids in the poly(ethylene glycol) 200 (PEG 200) solutions. Under UV radiation, the nanoSiO2–TPy linkers gave off an emission at about 366 nm (monomer of the linkers) in the PEG 200 solutions with the concentrations below 0.5 mg/mL, which shifted to 374 nm ...

Piezochromic Porous Metal-Organic Framework.

Pressure changes the color of a new type of metal-organic porous hybrid material CoBbcDabcoH2O. It is built of Co2+ cations linked by 1,4-benzenedicabroxylate (Bdc) anions and 1,4-diazabicyclo[2.2.2]octane (Dabco) molecules into 2-D grid-like sheets, interconnected through OH···O bonds of water molecules to carboxylate H-acceptors. This first piezochromic MOF, stable in air and in many solvents, is an ideal ultraprecise sensor for pressure calibration. The color changes are due to strains generated by pressure in the highly asymmetric crystal field of Co2+ octahedral coordination, involving four different ligand types: a Dabco amine (twice), a monodentate carboxylate, a chelating carboxylate, and a water molecule. At 0.33 GPa/296 K and below 225 K/0.1 MPa a phase transition reduces the crystal symmetry from monoclinic to triclinic system and changes the conformation and orientation of linkers.

Systematic pH-specific synthesis and structure transformations in binary-ternary In(III) assemblies with hydroxycarboxylic DPOT and aliphatic-aromatic chelators

Driven by the need to generate hybrid In(III)-(O,N) luminescent materials containing appropriately configured organic ligands, binary-ternary In(III) metal-organic systems involving the multidentate organic ligand DPOT, ethylenediamine (en) and phenanthroline (phen) were investigated under pH-specific conditions. The arisen materials [In2(C11H13N2O9)2](CH6N3)4·7H2O(1), [In3(C11H13N2O9)2(C2H8N2)2](C2H9N2)·4H2O(2), [In2(C11H13N2O9)2](CH6N3)6(Cl)2·6H2O(3), and [In2(C11H13N2O9)(C12H8N2)2(Cl)(H2O)]·7.5H2O(4) were characterized by analytical, spectroscopic (FT-IR, 13C-MAS NMR, luminescence) techniques, TGA and X-ray crystallography. The binary materials 1 and 3 exhibit dinuclear alkoxido-bridged In2O2 cores, with the fully-deprotonated organic ligand spanning both centers. Introduction of bidentate ethylenediamine leads to ternary trinuclear species 2, whereas phen introduction in 4 leads to a dinuclear asymmetric assembly, incorporating a chloride ion and a water molecule. Chemical transformations among 1–4 provide mechanistic insight into the nature of chelators, dictating nuclearity, coordination, composition and lattice-specific luminescence. The collective physicochemical properties in 1–4 present well-defined 1D-3D structural architecture-dimensionality and spectroscopic property correlations, pointing out criteria based on which synthon design, custom architecture and photoactivity are interwoven into the future development of In(III)-containing metal-organic hybrid materials.

Magnetic coupling in a hybrid Mn(ii) acetylene dicarboxylate.

The design of ligands that mediate through-bond long range super-exchange in metal-organic hybrid materials would expand chemical space beyond the commonly observed short range, low temperature magnetic ordering. Here we examine acetylene dicarboxylate as a potential ligand that could install long range magnetic ordering due to its spatially continuous frontier orbitals. Using a known Mn(ii)-containing coordination polymer we compute and measure the electronic structure and magnetic ordering. In this case, the latter is weak owing to the sub-optimal ligand coordination geometry, with a critical temperature of 2.5 K.

Elaboration of metal organic framework hybrid materials with hierarchical porosity by electrochemical deposition–dissolution

Rationally designed hierarchical macro-/microporous HKUST-1 electrodes were prepared via an electrochemical deposition–dissolution technique with the motivation to overcome diffusion limitations that typically occur for conventional microporous MOFs. A colloidal crystal of silica spheres was prepared by the Langmuir–Blodgett (LB) technique. Using this crystal as a template, macroporous copper electrodes with a controlled number of pore layers were prepared via electrodeposition. After the removal of the template, the synthesis of HKUST-1 was performed via partial anodic dissolution of the copper surface in the presence of an organic linker, leading to the deposition of HKUST-1 on the electrode surface with the designed macroporous structure. The macroporous Cu electrodes do not only behave as structural templates but are also the Cu source for the formation of MOFs. The applied potential and deposition time allow the characteristics of the porous layer to be fine-tuned. The developed synthesis is rapid, occurs under mild conditions and therefore opens up various potential applications including catalysis, separation and sensing based on these hierarchical materials.

Engineering the proton conductivity of metal–organic hybrid materials by varying the coordination mode of the ligand

We report the adjustment of proton conductivity by varying the coordination mode of a ligand.

Organics on oxidic metal surfaces: a first-principles DFT study of PMDA and ODA fragments on the pristine and mildly oxidized surfaces of Cu(111).

Metal-organic hybrid materials are ubiquitous and a fundamental understanding of the hybrid-interface is key for the development of these hybrid material systems. In this work, using first-principles density-functional theory (including van der Waals (vdW) corrections), we study the fundamental physico-chemical properties of the molecular fragments of pyromellitic dianhydride oxydianiline (PMDA-ODA) on pristine Cu(111), as well as oxidic p4:O/Cu(111) in order to investigate the effect of mild oxidation of the metal substrate on PMDA-ODA adsorption. Firstly, we report the most favorable adsorption geometries amongst the various surface models and correlate the adsorption behavior with the electronic structure of the molecular fragments and the substrate layer. PMDA adsorbs weakly on both the clean and mildly oxidized copper surface via vdW forces while ODA adsorbs much stronger with a significant charge transfer between the substrates. Here, the oxidic layer is found to reduce the adsorption strength of both fragments and in particular, the ODA molecule interacts with the substrate via additional hydrogen bonding. Finally, our simulated scanning tunneling microscopy (STM) images suggest possible orientations of PMDA and ODA on clean and oxidic Cu surfaces to guide future experiments.

Metal–organic hybrid materials built with tetrachlorophthalate acid and different N-donor coligands: Structure diversity and photoluminescence

Eight new metal–organic hybrid materials, namely {Cd(Tcph)(4,4′-bipy)1/2} (1), {[Cd2(Tcph)2(1,4-bimb)1/2(H2O)4]·H2O} (2), {Cd2(Tcph)2(1,4-bmimb)1/2(H2O)4} (3), {Cd(Tcph)(1,2-bmimb)} (4), {Cu(Tcph)(1,4-bimb)(H2O)} (5), {[Co(Tcph)(1,4-bimb)1/2(H2O)3]·(H2O)} (6), {Zn(Tcph)(1,2-bimb)} (7), {Cu2(Tcph)2(1,2-bimb)(H2O)4} (8), where Tcph=tetrachlorophthalate acid, 4,4′-bipy=4,4′-bipyridine, 1,4-bimb=1,4-bis(imidazol-1-ylmethyl)benzene, 1,4-bmimb=1,4-bis(2-methylimidazol-1-ylmethyl)benzene, 1,2-bimb=1,2-bis(imidazol-1-ylmethyl)-benzene, 1,2-bmimb=1,2-bis(2-methylimidazol-1-ylmethyl)benzene, have been synthesized and characterized. Their structures are determined by single crystal X-ray diffraction and further characterized by infrared spectra (IR) and thermogravimetric (TG) analyses. Complex 1, 4 and 7 display 2D layer structures. 1 possesses two-dimensional sheet containing an unusual [Cd(Tcph)] chains linked by 4,4′-bipy co-ligand, while 4 and 7 hold the similar 4-connected 44-sql nets. Complex 2 and 3 feature a similar three dimensional (3D) internal compensation structure with a topology of {42·63·8}2{63}. 5 is a novel 2-fold self-penetrating 3D network with 4-coordinated 65·8–CdSO4 subnets. The ladder-like chains of 6 are further connected through O–H···O interactions to yield a 3D supramolecular structure. 8 is a discrete tetranuclear complex. The thermal stabilities of 1–8 and the luminescent properties of 1–4 and 7 in the solid state are also discussed.

Resistive Switching Nanodevices Based on Metal–Organic Frameworks

AbstractSURMOF (surface‐anchored metal–organic frameworks) thin films exhibit exciting chemical and physical properties, which can be modulated in a straightforward fashion to achieve specific benefits for numerous applications in future technologies. Here, we report a detailed characterization of resistive switching in crystalline SURMOF films of around ≈10, ≈20 and ≈50 nm thicknesses. These demonstrated switching characteristics combined with the ability to deposit monolithically oriented crystalline HKUST‐1 films with well‐defined thicknesses in the nm‐range on conductive substrates serving as bottom electrodes and to lithographically fabricate top‐electrodes opens up the possibility to employ these metal–organic hybrid materials as solid state devices for potential nonvolatile resistive random access memory (RRAM) memory applications. MOF bipolar switching RRAM devices based on SURMOFs with thicknesses of 10±5 nm, 20±5 nm and 50±5 nm show exceptionally promising performance. The huge flexibility of MOF materials with regards to device applications is demonstrated by loading guest molecules into the pores of these framework materials. In the case of ferrocene infiltration, we show that the already impressive performance of the SURMOF‐RRAM devices can be further improved. The results demonstrate the great potential of SURMOF thin films for the implementation of novel and scalable active materials for the next generation of digital processing and organic‐based microelectronic devices.

Monolithic, Crystalline MOF Coating: An Excellent Patterning and Photoresist Material

AbstractMetal–organic frameworks, MOFs, are a class of crystalline porous metal–organic hybrid materials which have originally been developed for applications in gas storage and separation. Here, we demonstrate that due to the enormous chemical flexibility of these molecular materials, they also provide an excellent basis for the development of photoresist materials. In particular, we used an epitaxial process with automated systems to grow either homogeneous or patterned SURMOFs (surface‐anchored MOFs) of the type [Zn2(N3BPDC)2(Dabco)] on different solid substrates. The huge flexibility of the MOF chemistry allowed for different variants of photolithography based on the post‐synthesis modification (PSM) of the MOF materials. Here, two particular and popular PSM‐strategies were employed, the azide–alkyne click reaction and thiol–yne click chemistry. The azide–alkyne click reaction was initiated by the photoreduction of CuII to the active CuI catalyst, whereas the thiol–yne click chemistry was induced directly by UV light. Furthermore, heteroepitaxial growth of multilayer systems (Cu‐N3BPDC+Cu‐BPDC+Cu‐N3BPDC+Cu‐BPDC+Cu‐N3BPDC+Cu‐BPDC) was also used to control the localization of subsequent PSM. The results demonstrated that the patterned functionalization of MOF thin film is not limited to the two dimensions of the mounting surface but is indeed possible in 3D.

Novel metal-organic hybrid materials constructed by ferrocenyl terpyridine derivatives and ZnIIX2 (X = Cl−, Br−, I−, SCN− and CH3COO−)

Five novel Zinc (II) metal-organic hybrid materials, [(ZnCl2L)6·6(H2O)·6(CHCl3)] (1), [(ZnBr2L)6·6(H2O)·6(CHCl3)] (2), [ZnI2L·2(CHCl3)]n (3), [Zn(SCN)2L·(CHCl3)]n (4), and [Zn(CHCOO)2L·2(H2O)]n (5), have been assembled by a novel ligand 4′-ferrocenyl-4, 2′: 6′, 4″-terpyridine and different zinc salts under ambient conditions, and their structures have been confirmed by single-crystal X-ray diffraction analysis. The results indicate that both complexes 1 and 2 adopt a metallohexacycle consisting of six ligands and six zinc ions, and complexes 3, 4 and 5 are all one-dimensional polymers. The supramolecular frameworks are constructed by complexes 1–5 through the C–H⋯X (X = Cl, Br, I, S, O or π) or π–π intermolecular interactions. In addition, the optical band gaps were confirmed by use of the optical diffuse reflectance spectra, and the results show that the ligand and complexes 1–5 should have semiconductor properties.

Syntheses, Crystal Structures, and Magnetic Properties of Metal–Organic Hybrid Materials of Mn(II)/Co(II): Three-Fold Interpenetrated α-Polonium-like Network in One of Them

Three new 1,4-phenylenediacrylate bridged Mn(II) and Co(II) complexes of molecular formulas {[Mn2(ppda)(phen)4(H2O)2](ppda)2(H2O)} (1), {[Co(ppda)(dpyo)(H2O)3]·4(H2O)}n (2), and {[Co(ppda)(bpe)]·(0.5H2O)}n (3) [ppda = 1,4-phenylenediacrylate; phen = 1,10-phenanthroline; dpyo = 4,4′-dipyridyl N,N′-dioxide; bpe = 1,2-bis(4-pyridyl)ethane] have been synthesized and characterized by elemental analysis, IR spectra, single-crystal X-ray diffraction studies, and low-temperature magnetic measurements. The structural determination reveals that complex 1 is a discrete dinuclear species, 2 is a 1D polymeric chain, while 3 is a three-fold interpenetrated α-polonium network. Hydrogen-bonding interactions, formed by coordinated and/or lattice water molecules with ppda oxygen and π–π stacking interactions of aromatic rings, lead to a 3D supramolecular architecture in both complexes 1 and 2. Low-temperature magnetic study shows antiferromagnetic coupling in all the complexes. In addition, their electronic and fluorescent spectral properties have been investigated.

Facile synthesis of graphene oxide @ mesoporous carbon hybrid nanocomposites for lithium sulfur battery

We present a design and synthesis of a hierarchical architecture of graphene oxide @ mesoporous carbon (GO@Meso-C) using graphene oxide @ metal-organic framework hybrid materials (GO@MOF-5) as both the template and precursor. Active sulfur is encapsulated into the GO@Meso-C matrix prepared via carbonize GO@MOF-5 polyhedrons for high performance lithium sulfur battery. The initial and 100th cycle discharge capacity of GO@Meso-C/S sulfur cathode are as high as 1122 mAh g−1 and 820 mAh g−1 at a current rate of 0.2C. The remarkably high special capacity and capacity retention rate indicate that the GO@Meso-C is a promising host material for the sulfur cathode in the lithium sulfur battery applications.

A new metal–organic hybrid material with intrinsic resistance-based bistability: monitoring in situ room temperature switching behavior

Two new silver containing materials with TCNQ derivatives were prepared by electrocrystallization. Synchrotron radiation diffraction studies were conducted to determine the structures of the new phases which exhibit unprecedented high room temperature conductivity. The I–V characteristics reveal a room-temperature switching behaviour and memory effect based on intrinsic negative differential resistance (NDR). EPR spectroscopic measurements performed under an applied electric field indicate a g-tensor shift that is correlated to the amplitude of current.

Auxiliary ligand-controlled photochromism and decolourization of two bipyridinium-based metal–organic hybrid materials with various water clusters

Two bipyridinium-based metal–organic hybrid materials, {[Cd(Bpyen)0.5(p-BDC)(H2O)Br]·5H2O} (1) and {[Cd(Bpyen)(o-BDC)Br2]·8H2O} (2), have been synthesized. 1 is a 2D coordination polymer while 2 shows 1D chain-like structure. Both compounds exhibit rapid color change under light irradiation. However, the decolourization of the photochromic products is very different. The influence of the auxiliary ligands on the photochromism and decolourization process of the bipyridinium-based hybrid materials has been explored. Interestingly, water molecules are encapsulated in these two compounds and form novel water aggregates consisting of novel water building units, such as the (H2O)10 water cluster in 1 and the (H2O)12 water cages in 2 through hydrogen-bond interactions. The effect of these water aggregates on the stability of the two compounds has been studied.

Metal–Organic Organopolymeric Hybrid Framework by Reversible [2+2] Cycloaddition Reaction

Organic polymers are usually amorphous or possess very low crystallinity. The metal complexes of organic polymeric ligands are also difficult to crystallize by traditional methods because of their poor solubilities and their 3D structures can not be determined by single-crystal X-ray crystallography owing to a lack of single crystals. Herein, we report the crystal structure of a 1D Zn(II) coordination polymer fused with an organic polymer ligand made in situ by a [2+2] cycloaddition reaction of a six-fold interpenetrated metal-organic framework. It is also shown that this organic polymer ligand can be depolymerized in a single-crystal-to-single-crystal (SCSC) fashion by heating. This strategy could potentially be extended to make a range of monocrystalline metal organopolymeric complexes and metal-organic organopolymeric hybrid materials. Such monocrystalline metal complexes of organic polymers have hitherto been inaccessible for materials researchers.

Room temperature aqueous phase synthesis and characterization of novel nano-sized coordination polymers composed of copper(II), nickel(II), and zinc(II) metal ions with p-phenylenediamine (PPD) as the bridging ligand

Abstract Nanostructured metal-organic hybrid materials composed of nickel(II), copper(II), and zinc(II) metal ions and p-phenylenediamine (PPD) as the organic ligand were synthesized in aqueous medium at room temperature. The synthesized compounds were characterized by elemental analyses, powder X-ray diffraction (PXRD) spectra, Fourier transform infrared spectra, nuclear magnetic resonance (1H NMR) spectra, electronic spectra, scanning electron microscopy, N2 adsorption-desorption isotherm, and dynamic light scattering studies. N2 adsorption-desorption isotherm of copper(II)-PPD compound confirmed that it has mesoporous structure as it exhibits type-IV reversible isotherm with H1 hysterisis. Steep adsorption indicated that the mesopores possessing it are of uniform order. Barrett-Joyner-Halenda model showed an average pore diameter of 5.2 nm. The PXRD patterns of all the three compounds are identical and showed well-defined and highly intense diffraction peaks, thereby suggesting their nature as crystalline. The broadness of the diffraction peaks indicated that the particles are of nanometer dimensions.

Binary and Ternary Metal–Organic Hybrid Polymers in Aqueous Lead(II)–Dicarboxylic Acid–(Phen) Systems. The Influence of O- and S-Ligand Heteroatoms on the Assembly of Distinct Lattice Architecture, Dimensionality, and Spectroscopic Properties

Poised to understand the influence of O- and S-heteroatoms on the chemical reactivity of dicarboxylic acids toward Pb(II), leading to crystalline metal–organic hybrid materials with distinct lattice architecture, dimensionality, and spectroscopic properties, the synthesis and physicochemical properties of binary/ternary Pb(II)–(O,S)-dicarboxylic acid–(phenanthroline) systems was investigated in aqueous media. pH-specific hydrothermal reactions of Pb(II) with O- and S-dicarboxylic acid ligands and phenanthroline (phen) afforded the variable dimensionality metal–organic Pb(II) polymers [Pb3(oda)3]n (1), [Pb(phen)(oda)]n (2), [Pb(tda)]n (3), and [Pb(phen)(tda)]n (4). The choice of O- vs S-ligands in the aqueous systems of Pb(II) and phenanthroline is linked to the emergence of distinct lattice composition–dimensionality (2D–3D) changes at the binary and ternary level, bestowing spectroscopic fingerprint identity to Pb(II) coordination and luminescence activity.

Syntheses, Crystal Structures, and Magnetic Properties of Metal–Organic Hybrid Materials of Co(II) Using Flexible and Rigid Nitrogen-Based Ditopic Ligands as Spacers

A carboxylate-based flexible ligand, 5-(4-carboxybenzyloxy)isophthalic acid (p-cbiaH3), readily reacts with Co(II) salts in the presence of different pyridine-based coligands such as 4-bis(4-pyridinylmethyl)piperazine (bpmp) or 1,2-di(4-pyridyl)ethylene (dpe) under hydrothermal conditions to afford two different three-dimensional (3D) coordination polymers, {[Co4(OH)2(p-cbia)2(bpmp)-(H2O)3]·2H2O}n (1) and {[Co4(OH)2(p-cbia)2(dpe)(H2O)4]·2H2O}n (2). Both compounds have been characterized by X-ray crystallography, IR spectroscopy, thermogravimetry, and elemental analysis. Single-crystal X-ray diffraction studies reveal that both compounds consist of a tetranuclear core [Co4(μ3-OH)2]6+. Compound 1 is a unprecedented 3D non-interpenetrated (3,4,9)-connected pkb3 net. On the other hand, compound 2 is a 2-fold interpenetrated (3,8)-connected tfz-d net. Variable temperature static and dynamic magnetic measurements show that both compounds exhibit ferromagnetic behavior associated with mixed hydroxyl/carboxylate-...