Metal-organic Hybrid Materials Research Articles

Recent Advances in Room-Temperature Phosphorescence Metal-Organic Hybrids: Structures, Properties, and Applications.

Metal-organic hybrid (MOH) materials with room-temperature phosphorescence (RTP) have drawn attention in recent years due to their superior RTP properties of high phosphorescence efficiency and ultralong emission lifetime. Great achievement has been realized in developing MOH materials with high-performance RTP, but a systematic study on MOH materials with RTP feature is lacking. This review highlights recent advances in metal-organic hybrid RTP materials. The molecular packing, the photophysical properties, and their applications of metal-organic hybrid RTP materials are discussed in detail. Metal-organic hybrid RTP materials can be divided into six parts: coordination polymers, metal-organic frameworks (MOFs), metal-halide hybrids, organic ionic crystals, organic ionic polymers, and organic-inorganic hybrid perovskites. These RTP materials have been successfully applied in time-resolved data encryption, fingerprint recognition, information logic gates, X-ray imaging, and photomemory. This review not only provides the basic principles of designing RTP metal-organic hybrids, but also propounds the future research prospects of RTP metal-organic hybrids. This review offers many effective strategies for developing metal-organic hybrids with excellent RTP properties, thus satisfying practical applications.

N-heterocyclic carbene adsorption states on Pt(111) and Ru(0001).

N-heterocyclic carbene ligands (NHCs) are increasingly used to tune the properties of metal surfaces. The generally greater chemical and thermal robustness of NHCs on gold, as compared to thiolate surface ligands, underscores their potential for a range of applications. While much is now known about the adsorption geometry, overlayer structure, dynamics, and stability of NHCs on coinage elements, especially gold and copper, much less is known about their interaction with the surfaces of Pt-group metals, despite the importance of such metals in catalysis and electrochemistry. In this study, reflection absorption infrared spectroscopy (RAIRS) is used to probe the structure of benzimidazolylidene NHC ligands on Pt(111) and Ru(0001). The experiments exploit the intense absorption peaks of a CF3 substituent on the phenyl ring of the NHC backbone to provide unprecedented insight into adsorption geometry and chemical stability. The results also permit comparison with literature data for NHC ligands on Au(111) and to DFT predictions for NHCs on Pt(111) and Ru(0001), thereby greatly extending the known surface chemistry of NHCs and providing much needed molecular information for the design of metal-organic hybrid materials involving strongly reactive metals.

Role of Transition Metals in Metal-Organic Frameworks as Nanoporous Ion Emitters for Thermal Ionization Mass Spectrometry.

Thermal ionization mass spectrometry is a powerful analytical technique that allows for precise determination of isotopic ratios. Analysis of low abundance samples, however, can be limited by the ionization efficiency. Following an investigation into a new type of metal-organic hybrid material, nanoporous ion emitters (nano-PIEs), devised to promote the emission of analyte ions and reduce traditional sample loading challenges, this work evaluates the impact that changing the metal in the material has on the ionization of uranium (U). Being derived from metal-organic frameworks (MOFs), nano-PIEs inherit the tunability of their parent MOFs. The MOF-74 series has been well studied for probing the impact various framework metals (i.e., Mg, Mn, Co, Ni, Cu, Zn, and Cd) have on material properties, and thus, a series of nano-PIEs with different metals were derived from this isoreticular MOF series. Trends in ionization efficiency were studied as a function of ionization potential, volatility, and work function of the framework metals to gain a better understanding of the mechanism of analyte ionization. This study finds a correlation between the analyte ionization efficiency and nano-PIE framework metal volatility that is attributed to its tunable thermal stability and degradation behavior.

High performance Hetero-Shelled hollow structure Metal-Organic framework hybrid material for the efficient electrochemical determination of lead ions

Electrochemical sensing has unique advantages in developing on-site and online detection technologies for heavy metal ions (HMIs) due to its fast response, simple operation, high sensitivity, and portable instruments. The vigorous development of modern micro/nanomaterial preparation technology has provided greater space for improving the performance of electrochemical sensing platforms. In this work, a novel hetero-shelled hollow structure metal–organic framework (MOF) hybrid material (denoted as HCZ@UN) was prepared by adopting the hollow carbonized ZIF-8 (HCZ) as the substrate for growing UiO-66(Zr)–NH2 (UN), and subsequently used for efficient electrochemical detection of lead ions (Pb2+). The grown UN crystal particles were anchored on the HCZ hollow cages and showed nanometer size. The unique shell structure and nanometer size of UN created large specific surface area and rich accessible adsorption sites, which promoted the preconcentration of Pb2+. While the hollow carbon polyhedron structure of HCZ improved the dispersibility of UN and electron transfer ability of the material. These factors synergistically improved the detection sensitivity and sensing performance for Pb2+ determination with a wide linear range of 0.100–500 nM, a low detection limit of 0.0492 ± 0.00523 nM as well as good selectivity, repeatability and long-term stability. This paper provides a simple and effective method for the preparation of electroactive MOF functional materials, which is expected to inspire more interest in building other MOF-based materials with unique structure, high-performance and extensive application value.

Bioconjugation in Materials Science

AbstractWith the advent of bioconjugation chemistry in the last two decades, highlighted by the Nobel Prize 2022, the quest for possible novel applications has been greatly intensified, broadening the prospects of these mostly simple, specific, and high‐yield reactions. The advancement of bioconjugation methods is anticipated to expand the scope of bioinstructive and bioadaptive materials science in the future. This perspective article will discuss the reactions developed in this research area over the last 10 years for coupling various biological entities such as polysaccharides, oligonucleotides, peptides, and proteins. Building on this, the impact of bioconjugation reactions in materials science and 3D printing, including their challenges and requirements is shown. Established procedures for modifying molecular structures such as Covalent and Metal Organic Frameworks (COF/MOF) or hybrid materials for biomedical applications and the scope for future research and optimization will be presented.

Titelbild: Guiding Principles for the Rational Design of Hybrid Materials: Use of DFT Methodology for Evaluating Non‐Covalent Interactions in a Uranyl Tetrahalide Model System (Angew. Chem. 33/2023)

Uranyl tetrahalide ions assemble into hybrid material through Non-Covalent Interactions (NCIs) in the presence of organic charge balancing cations. NCIs such as hydrogen bonding serve to stabilize these supramolecular hybrid complexes and act as the fundamental driving force for crystallization. In their Research Article (e202305073), Sara E. Mason, Tori Z. Forbes et al. employed these hybrid complexes as a model system to assess the effect of NCIs on the vibrational properties and formation enthalpies of metal–organic hybrid materials.

Cover Picture: Guiding Principles for the Rational Design of Hybrid Materials: Use of DFT Methodology for Evaluating Non‐Covalent Interactions in a Uranyl Tetrahalide Model System (Angew. Chem. Int. Ed. 33/2023)

Uranyl tetrahalide ions assemble into hybrid material through Non-Covalent Interactions (NCIs) in the presence of organic charge balancing cations. NCIs such as hydrogen bonding serve to stabilize these supramolecular hybrid complexes and act as the fundamental driving force for crystallization. In their Research Article (e202305073), Sara E. Mason, Tori Z. Forbes et al. employed these hybrid complexes as a model system to assess the effect of NCIs on the vibrational properties and formation enthalpies of metal–organic hybrid materials.

A Novel Molecular Assembly of a Cobalt-Sulfate Coordination Polymer and Melamine: A Manifestation of Magnetic Anisotropy.

A novel molecular assembly of a cobalt-sulfate coordination polymer and melamine is synthesized under acidic conditions. Bar-shaped pink monocrystals as long as 1 mm are found to align along magnetic field lines in the proximity of a strong magnet. Magnetometry shows no hysteresis at temperatures down to 2 K but instead magnetic anisotropy and antiferromagnetic coupling. X-ray diffraction on a single crystal reveals that the cobalt-sulfate chains are along the shortest lattice vector or the crystal's long axis. The crystal alignment along the magnetic flux can be attributed to single-ion anisotropy that results in longitudinal antiferromagnetic coupling along the chain. Both structurally and magnetically isotropic crystals of metal-organic hybrid materials can be highly useful as elemental components in magneto-optics.

Lead Looping for Low-Temperature CO2 Capture and Release

The sustainable use of metal oxides to rapidly capture and release CO2 as a C1 building block at a low energy cost is appealing yet challenging. Herein, we show that vicinal diols (e.g., ethylene glycol, glycerol, and 1,2-propanediol) can significantly accelerate the carbonation rates of PbO at ambient conditions, accompanied by a CO2 uptake capacity (567 mmol mol–1) comparable to that of the frequently used CaO and MgO. It is revealed that the in situ generated metal–organic hybrid materials of PbO and vicinal diols are the key intermediates for the reaction cycle. They can rapidly react with CO2 to generate PbCO3, accompanied by the release of vicinal diols for the next reaction cycle. The accelerated CO2 capture at ambient conditions coupled with the easy regeneration of PbO and release of CO2 via calcination of PbCO3 at a low temperature (∼300 °C) constitutes a new lead looping process with low energy input.

Charge-transfer regulated visible light driven photocatalytic H2 production and CO2 reduction in tetrathiafulvalene based coordination polymer gel

The much-needed renewable alternatives to fossil fuel can be achieved efficiently and sustainably by converting solar energy to fuels via hydrogen generation from water or CO2 reduction. Herein, a soft processable metal-organic hybrid material is developed and studied for photocatalytic activity towards H2 production and CO2 reduction to CO and CH4 under visible light as well as direct sunlight irradiation. A tetrapodal low molecular weight gelator (LMWG) is synthesized by integrating tetrathiafulvalene (TTF) and terpyridine (TPY) derivatives through amide linkages and results in TPY-TTF LMWG. The TPY-TTF LMWG acts as a linker, and self-assembly of this gelator molecules with ZnII ions results in a coordination polymer gel (CPG); Zn-TPY-TTF. The Zn-TPY-TTF CPG shows high photocatalytic activity towards H2 production (530 μmol g−1h−1) and CO2 reduction to CO (438 μmol g−1h−1, selectivity > 99%) regulated by charge-transfer interactions. Furthermore, in situ stabilization of Pt nanoparticles on CPG (Pt@Zn-TPY-TTF) enhances H2 evolution (14727 μmol g−1h−1). Importantly, Pt@Zn-TPY-TTF CPG produces CH4 (292 μmol g−1h−1, selectivity > 97%) as CO2 reduction product instead of CO. The real-time CO2 reduction reaction is monitored by in situ DRIFT study, and the plausible mechanism is derived computationally.

Structural insights into coordination polymers based on 6s2 Pb(II) and Bi(III) centres connected via heteroaromatic carboxylate linkers and their potential applications

Studies on coordination chemistry published over the last 20 years, have led to increased interest in coordination polymers (CPs). This interest has been generated not only by the intriguing structures of metal–organic hybrid materials but also by their potential applications in many fields such as luminescence, nonlinear optics, gas adsorption, catalysis, magnetism, and bioimaging. To appropriately design new materials for the chosen applications we identified the main goal of the published literature research, which was to understand the relationship between the composition and structure on the molecular and crystal levels and the properties of coordination polymers. Overall, in this review we focused on the three main topics concerning Pb(II) and Bi(III) polymers: i) coordination modes of linkers, ii) central ion lone electron pair stereoactivity, iii) topology, and potential applications. Given a comprehensive review of the literature, we examined the differences and similarities of polymers composed of i) 5- and 6-membered N-, S-, and O-heteroaromatic carboxylates, ii) linkers with mono- or dicarboxylate functional groups, and iii) isomers as linkers (e.g., the effect of the carboxylate group position). Such versatility of ligands plays a crucial role in modulating structure and topology, which directly influencing the potential application of the designed coordination polymers (e.g., as fluorescence materials). Other important structural components of CPs discussed in this review are the Pb(II) and Bi(III) ions. Both have several advantages: i) a large ionic radius, ii) a wide range of coordination numbers, and iii) the effect of 6s2 lone electron pair stereoactivity (holo- or hemidirected geometry). Moreover, there will be emphasized the significant role of noncovalent interactions (e.g. tetrel and pnictogen bonds), which simultaneously stabilized structure, expanded dimensionality, and finally, influenced physicochemical properties.

Fabrication of chromium based metal organic framework (MIL-101)/activated carbon composites for acetylation of glycerol

Chromium based metal organic framework (MIL-101)/activated carbon composite materials were synthesized using hydrothermal method and the catalytic effect was investigated for the acetylation of glycerol with acetic acid. Activated carbon and chromium based metal organic framework hybrid material was fabricated with two different weight ratio of chromium ion to activated carbon, materials were labelled as AC@MIL-10110, AC@MIL-1015. The characterization of synthesized catalysts was performed using XRD, N2 adsorption, TGA, FTIR, SEM/EDS, XPS, n-butylamine titration, contact angle measurement and TEM in order to explore the relation between the structure and catalytic performance. The effect of addition of the activated carbon on the catalytic activity of materials was determined by considering conversion of glycerol and selectivity of glycerol monoacetate, glycerol 1,3 diacetate and glycerol triacetate. Taguchi orthogonal L9 matrix has been applied to understand the effect of temperature, molar ratio and catalyst loading on the conversion of glycerol and selectivity of acetates. Signal to noise ratio (S/N) and analysis of variance (ANOVA) results revealed that the temperature was the dominant factor affecting the conversion and selectivity. 100% of glycerol was converted to acetates and 5.2% of glycerol triacetate selectivity was achieved at 110 °C, acetic acid/glycerol molar ratio of 9 and catalyst loading of 4 g/L.

1D-2D Ag nanowire/g-C3N4 hybrid obtained via a post-mechanical-mixing route for photocatalytic Rhodamine B degradation

The photocatalytic degradation of Rhodamine B (Rh B) wastewater using Ag/g-C3N4 composites has aroused great interests. To date, the composite is dominated by Ag nanoparticles (AgNPs) on the g-C3N4 surface. Only a few studies have concentrated on 1D Ag nanowires (AgNWs) wrapped with g-C3N4 which could bring some new aspects. The wrapped structures can provide large interface, which promotes the exciton dissociation. Moreover, AgNWs with high conductivity can facilitate a fast charge transfer from g-C3N4 and therefore suppress the charge recombination. Herein, a facile approach via a post-mechanical-mixing route has been used to fabricate 1D-2D AgNWs/g-C3N4 composites with enhanced photocatalytic activity for Rh B degradation. AgNWs staggered arrangement can form a conductive network for fast charge transfer. The light absorption of the hybrid in the visible-light region is increased due to the light-scattering from 1D AgNWs. Moreover, conformal contact between AgNWs and g-C3N4 promotes the separation of photo-induced electron-hole pairs. The AgNWs/g-C3N4 hybrid for 2 wt% achieves the best photocatalytic activity for Rh B dye degradation. This work reports an idea using 1D–2D metal-organic hybrid materials as photocatalysts and proposes a facile post-mechanical-mixing method for fabricating hybrids toward various applications.

Recent Progress on Luminescent Metal-Organic Framework-Involved Hybrid Materials for Rapid Determination of Contaminants in Environment and Food.

The high speed of contaminants growth needs the burgeoning of new analytical techniques to keep up with the continuous demand for monitoring and legislation on food safety and environmental pollution control. Metal-organic frameworks (MOFs) are a kind of advanced crystal porous materials with controllable apertures, which are self-assembled by organic ligands and inorganic metal nodes. They have the merits of large specific surface areas, high porosity and the diversity of structures and functions. Latterly, the utilization of metal-organic frameworks has attracted much attention in environmental protection and the food industry. MOFs have exhibited great value as sensing materials for many targets. Among many sensing methods, fluorometric sensing is one of the widely studied methods in the detection of harmful substances in food and environmental samples. Fluorometric detection based on MOFs and its functional materials is currently one of the most key research subjects in the food and environmental fields. It has gradually become a hot research direction to construct the highly sensitive rapid sensors to detect harmful substances in the food matrix based on metal-organic frameworks. In this paper, we introduced the synthesis and detection application characteristics (absorption, fluorescence, etc.) of metal-organic frameworks. We summarized their applications in the MOFs-based fluorometric detection of harmful substances in food and water over the past few years. The harmful substances mainly include heavy metals, organic pollutants and other small molecules, etc. On this basis, the future development and possible application of the MOFs have prospected in this review paper.

Expandable Layered Hybrid Materials Based on Individual 1D Metalorganic Nanoribbons.

Different metalorganic lamellar hybrid materials based on associated nanoribbons were synthesized by the use of alkyl–benzyl monocarboxylate spacers, containing alkyl tails with variable lengths, which acted like structural growing inhibitors. These molecular agents were perpendicularly located and coordinated to aluminium nodes in the interlayer space, controlling the separation between individual structure sub-units. The hybrid materials were studied by X-ray diffraction (XRD), chemical and thermogravimetrical analysis (TGA), nuclear magnetic resonance (NMR) and infrared spectroscopy (IR), and field emission scanning electron microscopy (FESEM)/transmission electron microscopy (TEM), showing their physicochemical properties. The specific capacity of the metalorganic materials to be exfoliated through post-synthesis treatments, using several solvents due to the presence of 1D structure sub-units and a marked hydrophobic nature, was also evidenced.

Chemical sensor using metal-organic complex: Preparation, characterization and application for highly selective detection of cyanide ions in mixed aqueous-organic media

In this study, a novel metal-organic hybrid material (MO1) was designed and synthesized for the detection of CN− ions. The spectral analyses by FT-IR, 1H NMR, 13C NMR, CHN and TGA satisfactorily confirmed the structure of MO1. The sensor MO1 was applied as colorimetric probe for sensing of cyanide ions in aqueous solutions of dimethyl sulfoxide. MO1 with electron withdrawing group at organic ligand showed high selectivity for detection of cyanide over other interfering anions. Interaction of MO1 with cyanide provides obvious colorimetric change from red to violet, enabling easy detect with the naked eye. In addition, the sensing details were evaluated using UV–vis spectroscopy. Furthermore, the detection limit of chemosensor toward CN‾ ions was found to be 5.52 μM. Moreover, probe MO1 can be used for selective sensing of cyanide based on the obvious color changes in real samples.

Interfacial self-assembly of bipyridyl-functionalized nanoSiO2-BPy@Ln(β-diketone)n composites and their luminescent properties

Interfacial self-assembly provides an effective route to design and construct various metal-organic hybrid and composite materials with interesting optical and electroactive properties. Here, we reported the interfacial self-assembly of luminescent nano-composites through the coordination reaction of lanthanide salts of Ln(CF3SO3)3 (Ln = Eu and Tb) with the 2,2′-bipyridyl (BPy)-functionalized silica nano-linkers (nanoSiO2-BPy) and several β-diketone ligands. The assembling processes and the nano-materials as-prepared were characterized by using thermogravimetry, infrared, UV–vis absorption and X-ray photoelectron spectroscopy, as well as field emission transmission electron microscopy (FE-TEM). The luminescent properties from both nanoSiO2-BPy linkers and lanthanide nano-composites were investigated in the solutions and solid powders, which revealed not only the broad emissions of nanoSiO2-BPy linkers between 400 and 520 nm, but also the sharp emissions between 480 and 750 nm, designated to the 4f–4f electron transitions of 5D4 → 7Fn (n = 3,4,5,6) and 5D0 → 7Fn (n = 0,1,2,3,4) of the Tb3+ and Eu3+ ions, respectively. The relative emission intensity of the Ln3+ ions in the nano-composites has been found to be closely dependent on the compositions of the nano-composites, structure of the β-diketone ligands, and the excited wavelengths. Finally, the energy transfer process in the nano-composites was discussed.

Preparation, Characterization, and Catalytic Property of a Cu(II) Complex with 2-Carboxybenzaldehyde-p-Toluenesulfonyl Hydrazone Ligand

Metal-organic complex hybrid materials constructed from carboxylate ligands and hydrazone ligands have exhibited potential application in many fields. In order to enrich the applications of the metai-organic complex materials, a new hydrazone ligand contains carboxylate group, 2-carboxybenzaldehyde-p-toluenesulfonyl hydrazone (L1), and its Cu(II) complex (C2), have been prepared. The structure of L1 was determined by elemental analysis, IR spectra and single crystal X-ray diffraction, and the composition of Cu(II) complex (C2) has also been determined by elemental analysis, IR and UV spectra. The catalytic activity for A3 coupling reaction of benzaldehyde, piperidine, and phenylacetylene has been investigated. The results show that Cu(II) complex displays a 100 % selectivity to the product of propargylamine during A3 coupling reaction and benzaldehyde conversions were 95.3, 94.2, and 93.4 % at 120 °C for 12 h in the first, second, and third reaction cycles, respectively.

Microporous metal organic framework-based copolymers with efficient gas adsorption capability and high temporal stability

We report new microporous metal-organic 3D coordinated copolymers that exhibit both highly efficient gas adsorption capability and high temporal stability. The Zn-coordinated copolymers (MBCn) were prepared by mixing two organic ligands at various molar ratios: the widely used benzenedicarboxylate (BDC) and its analogous Cn-acid with non-polar alkoxy side chains of various lengths. All MBCn copolymers bearing alkoxy side chains exhibited identical framework structures to that of MOF-5 prepared with only the BDC ligand. Interestingly, compared to MOF-5, MBCn copolymers exhibited up to three times higher gas adsorption properties and higher temporal structural stability. Therefore, copolymerization with organic ligands bearing alkoxy side chains is a promising strategy for the development of new microporous metal-organic hybrid materials. Open image in new window

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.