Metal-organic Clusters Research Articles

Comparative study of metal-organic frameworks synthesized via imide condensation and coordination assembly.

A series of metal-organic frameworks (1-XDI) have been synthesized by imide condensation reactions between an amine-functionalized pentanuclear zinc cluster, Zn4Cl5(bt-NH2)6, (bt-NH2 = 5-aminobenzotriazolate), and organic dianhydrides (pyromellitic dianhydride (PMDA), naphthalenetetracarboxylic dianhydride (NDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (HFIPA)). The properties of the 1-XDI MOFs have been compared with analogues (2-XDI) prepared using traditional coordination assembly. The resulting materials have been characterized by ATR-IR spectroscopy, acid-digested 1H NMR spectroscopy, elemental analysis, and gas adsorption measurements. N2 adsorption isotherm data reveal modest porosities and BET surface areas (30-552 m2 g-1). All of the new 1-XDI and 2-XDI MOFs show selective adsorption of C2H2 over CO2 while 2-PMDI and 2-BPDI exhibit high selectivity toward C3H6/C3H8 separation. This study establishes imide condensation of preformed metal-organic clusters with organic linkers as a viable route for MOF design.

Advancing Single-Particle Analysis in Synthetic Chemical Systems: A Forward-Looking Discussion.

Single-particle analysis (SPA) is a fundamental method of cryo-electron microscopy developed to resolve the structures of biological macromolecules. This method has seen significant success in structural biology, yet its potential applications in synthetic chemical systems remain underexplored. In this perspective article, SPA and associated electron microscopy techniques are first briefly introduced. It is then proposed that SPA is well-suited for structural analysis of chemical systems where discrete, identical macromolecules can be readily obtained. Applicable systems include various clusters such as coinage metal clusters, metal-oxo/sulfur clusters, metal-organic clusters, and supramolecular compounds like coordination cages and metallo-supramolecular cages. When high-quality large single crystals are unattainable, SPA provides an alternative method for determining their structures. Beyond these end products, it is suggested that SPA can be instrumental in studying synthetic intermediates of materials with specific building units, such as metal-organic frameworks and zeolites. Given that various intermediates coexist in the reaction system, a purification step is necessary before conducting SPA, which can be facilitated by soft-landing electrospray ionization mass spectrometry.

Mechanically Robust, Durable, and Multifunctional Hyper-Crosslinked Elastomer Based on Metal-Organic-Cluster Crosslinker: The Role of Topological Structure.

Polymer materials formed by conventional metal-ligand bonds have very low branch functionality, the crosslinker of such polymer usually consists of 2-4 polymer chains and a single metal ion. Thus, these materials are weak, soft, humidity-sensitive, and unable to withstand their shape under long-term service. In this work, a new hyperbranched metal-organic cluster (MOC) crosslinker containing up to 16 vinyl groups is prepared by a straightforward coordination reaction. Compared with the current typical synthesis of metal-organic cages (MOCs) or metal-organic-polyhedra (MOP) crosslinkers with complex operations and low yield, the preparation of the MOC is simple and gram-scale. Thus, MOC can serve as a high-connectivity crosslinker to construct hyper-crosslinked polymer networks. The as-prepared elastomer exhibits mechanical robustness, creep-resistance, and humidity-stability. Besides, the elastomer possesses self-healing and recyclability at mild condition as well as fluorescence stability. These impressive comprehensive properties are proven to originate from the hyper-crosslinked topological structure and microphase-separated morphology. The MOC-driven hyper-crosslinked elastomers provide a new solution for the construction of mechanically robust, durable, and multifunctional polymers.

Controlling the structural and adsorption features of polyoxovanadate-based metal–organic clusters by adjustable template effect

An adjustable template effect was employed to activate the evolution of polyoxovanadate-based metal–organic clusters, resulting in unprecedented structural archetypes as well as customized dye and iodine adsorption features.

Designed metal-organic π-clusters combining the aromaticity of the metal cluster and ligands for a third-order nonlinear optical response.

The pivotal role of clusters and aromaticity in chemistry is undeniable, but there remains a gap in systematically understanding the aromaticity of metal-organic clusters. Herein, this article presents a novel metal-organic π-cluster, melding both metal-organic chemistry and aromaticity, to guide the construction of structurally stable Os-organic π-clusters. An in-depth analysis of these clusters reveals their bonding attributes, π-electronic composition, and origins of aromaticity, thereby confirming their unique metal-organic π-cluster properties. Furthermore, the Os5 cluster exhibits a promising third-order nonlinear optical (NLO) response, attributable to its narrow band gap and uniform electron/hole distribution, suggesting its potential as an optical switching material. This research introduces a fresh perspective on clusters, centered on delocalization, and broadens the domain of aromaticity studies. It also presents a novel method for designing efficient third-order NLO materials through consideration of the structure-activity relationship.

Systematic design and functionalisation of amorphous zirconium metal-organic frameworks.

Controlling the structure and functionality of crystalline metal-organic frameworks (MOFs) using molecular building units and post-synthetic functionalisation presents challenges when extending this approach to their amorphous counterparts (aMOFs). Here, we present a new bottom-up approach for synthesising a series of Zr-based aMOFs, which involves linking metal-organic clusters with specific ligands to regulate local connectivity. In addition, we overcome the limitations of post-synthetic modifications in amorphous systems, demonstrating that homogeneous functionalisation is achievable even without regular internal voids. By altering the acidity of the side group, length, and degree of connectivity of the linker, we could control the porosity, proton conductivity, and mechanical properties of the resulting aMOFs.

Sustainable cutting-edge techniques for gold valorization from electronic wastes

In recent years, electronic waste (E-waste) has emerged as a severe risk to worldwide environmental security and human health because it contains many hazardous chemicals of heavy metals, plastics, flame retardants, etc. Notably, gold – one of the noblest metals – consisted of E-waste that can be reused not only to save natural resources but also to curtail the harsh effect on the environment of mineral exploitation and engineering new products in the future. Highly porous material platforms made up of either metal ions or organic ligand-linked clusters have gained attention owing to specific properties including high surface area, tunable pore sizes, and the ability to selectively adsorb gold ions. This review discusses the recent advances and progress of porous structure-based materials for the recent application in recycling gold from E-waste. Moreover, the current difficulties and future advancements of novel and unique porous structure-introduced platforms in recycling gold derived from E-waste are also discussed by exhibiting reusability, high selectivity, stability, and easiness in handling.

Pyrolysis of Schiff‐Base Manganese Clusters: Effect of Ligand Modulation on the Performance of Supercapacitor Electrodes

AbstractLigand modulation on metal organic clusters endow them with different physical and chemical properties, while how ligand modulation further affects the electrochemical behavior of pyrolytic derivatives is still unclear. Herein, we constructed two trinuclear manganese clusters 1‐Mn3 [Mn3L12(Cl)2] [L1=N1,N3‐bis(3‐methoxysalicylidene) diethylenetriamine] and 2‐Mn3 [Mn3L22(C7H4O2)2] [L2=N1,N3‐bis(3‐salicylidene) diethylenetriamine] based on nitrogen‐rich Schiff‐base pentadentate ligands. The introduction of TG‐MS (thermogravimetry associated with mass spectroscopy) explores the difference and universality of the pyrolysis mechanism of two trinuclear manganese clusters, and divides the pyrolysis process into three Areas (Area I/II/III) according to temperature. Combined with other characterization techniques, the materials in these three areas were analyzed to explain the effect of ligand modification on the electrochemical properties of cluster pyrolysis derivatives. It is found that the Area III derivatives have the best capacitance performance, when the current density is 1 A g−1, the specific capacitance of 1‐900 is 1717 F g−1, and 2‐900 is 350 F g−1. By comparison of the phase evolution process and electrochemical performance of the two manganese clusters, it is proposed that the crumbling of the molecular structure and stacking mode of trinuclear manganese clusters during pyrolysis will affect the capacitive properties of the derivatives. This work provides a guidance for the differences of the properties of pyrolytic derivatives under ligand modulation.

Molecular modelling framework of metal-organic clusters for conserving surfaces: Langmuir sorption through the TD-DFT/ONIOM approach

ABSTRACT The Langmuir adsorption model of some organic inhibitors containing benzotriazole (BTA), 8- hydroxyquinoline (8-HQ), and 2-mercaptobenzothiazole (2-MBT) onto the Al-X (X=Mg, Ga, Si) alloy surface.The ONIOM method has been accomplished with a three-layered step of high level of DFT method using EPR-III, 6-31+G (d,p) and LANL2DZ basis sets. NMR spectroscopy has indeed concentrated on the Al shielding in the intra-atomic interaction with Mg, Ga and Si and meanwhile interatomic interaction with other atoms in BTA, 8-HQ, and 2-MBT compounds. Aluminum-silicon binary alloy with highest changes in the shielding tensors of NMR spectrum produced by intra-atomic interaction directs us to the most penetration in the neighbor atoms created by interatomic reaction. IR computations based on comparing the amounts has exhibited that 2-MBT with high stability based on its active zone of sulfur atoms and high molecular size shows high corrosive inhibition as 2-MBT →Al-Ga>Al-Mg ≈ Al-Si. Furthermore, BTA with nitrogen atom and 8-HQ with oxygen atom can coat the Al-X (X=Mg/Ga/Si) alloys surface through Langmuir adsorption as BTA →Al-Ga>Al-Mg ≈ Al-Si, and 8-HQ →Al-Ga>Al-Mg ≈ Al-Si, respectively. Moreover, it has been observed that the inhibition yield is ordered as: Al-Ga> Al-Mg ≈ Al-Si.

Ultrasensitive metal-organic cluster resist for patterning of single exposure high numerical aperture extreme ultraviolet lithography applications

BackgroundAn incredible increase in the integration of electronic chips has pushed the semicon industries to endorse high numerical aperture (h-NA ∼ 0.5), extreme-ultraviolet (EUV) lithography (EUVL) (λ ∼ 13.5 nm) at the commercial scale. Induction of h-NA postulates EUV resists that could outperform the resolution, line pattern roughness, and sensitivity (RLS) trade-off for chip fabricators, which is currently extremely limited.AimThe development of EUV resist to balance RLS trade-off as well as overcome throughput limitations of h-NA EUV system to facilitate high volume semiconductor manufacturing.ApproachHere, we developed indium-methacrylic acid-based metal-organic clusters resist for h-NA, EUVL. To examine the h-NA single exposure patterning potential of the resist, prescreening by sub-10 nm next-generation lithography (NGL) tools such as electron beam lithography (EBL), and helium ion beam lithography (HIBL) were conducted as a prelude to EUV exposure.ResultsDense ∼13 nm, (l/s) patterns at ∼45 and ∼30 μC / cm2 were well resolved by EBL and HIBL, on the top this the line edge roughness (LER) was 2.48 ± 0.04 nm, and etch resistance ∼1.98 and ∼0.34 times lower than Si and SiO2 / Si systems. Also, In-MAA MOCs resist shows ultra-sensitivity of 2.3 mJ / cm2 towards h-NA EUVL for patterning up to 26 nm half-pitch line patterns with LER ∼2.36 ± 0.16 nm.

Chiral Metal–Organic Cluster Induced High Circularly Polarized Luminescence of Metal–Organic Framework Thin Film

AbstractGuest‐induced host–guest assembly in metal–organic frameworks (MOFs) has become a critical strategy to achieve circularly polarized luminescence (CPL). Herein, chiral metal–organic clusters (MOCs) induced CPL of achiral MOF are reported. Enantiopure titanium‐oxo clusters (R/S‐TOCs) are effectively loaded into the pores of a fluorescent, highly stable MOF NU‐901 thin film by using a liquid‐phase epitaxial layer‐by‐layer encapsulation method. The resulting chiral TOCs@NU‐901 MOF thin films exhibit strong chirality, intense photoluminescence, and excellent CPL performance with the highest dissymmetry factor (±0.025) reported so far for the downshifted MOF‐based materials. Further, the comparison experiments and density functional theory (DFT) calculations demonstrate that the excellent performance benefited from the strong chirality and charge transfer caused by the significant π–π interactions between the host (MOF) and guest (R/S‐TOCs). This novel chiral MOCs induced approach provides a powerful toolbox for new host–guest CPL thin film materials.

Polymer metal-organic clusters based on hyperbranched polyester polybenzoylthiocarbamate and Cu(II) and Co(II) ions

Polymer metal-organic framework (MOF) are a new class of hybrid porous materials that combine the advantages of both organic polymers and metal-organic frameworks. In this regard, a new ligand was synthesized - a hyperbranched polyester polybenzoylthiocarbamate, the structure of which was established by IR, 1H NMR, electron spectroscopy and elemental analysis. Complexing properties have been studied using the example of Cu(II) and Co(II) ions. The formation of metal-polymer clusters with metal ions with the participation of benzoylthiocarbamate groups of the polyester has been proved by IR, electron spectroscopy and electron microscopy. It was found that the structure of coordination sites is octahedral with tetragonal distortions. The compositions and conditional logarithms of the stability constants of the complexes were determined.

Morphology controlled synthesis of yttrium metal–organic frameworks with a tritopic ligand

Metal-Organic Frameworks (MOFs) are extended three-dimensional metal–organic clusters created by the self-assembly of metal ions with organic ligands, whose repeated unit spreads in space very orderly. Yttrium based 3D network structure, have been synthesized using the tritopic organic linker 1,3,5-benzenetricarboxylic acid (H3-BTC) adopting a one-pot, green approach through a fine tuning of the process parameters like temperature and time. The syntheses have been carried out at various temperatures and reaction times, in order to correlate the morphological and structural features to the synthetic conditions. The synthesized Y-BTC samples have been studied in detail through powder X-ray diffraction (PXRD) and FT-IR spectroscopy in order to analyse the 3D structure arrangements. Specifically, the Y-BTC PXRD patterns have been compared with patterns derived from literature data. The Y-BTC sample synthesized at room temperature for 24 h has the same structure of the known Y(BTC)(H2O)6 compound, while the Y-BTC produced at high temperature for 24 h has a new structure, whose cell parameters are a = 14.668(2) Å, b = 16.316(2) Å, and c = 6.9650(4) Å. Field emission scanning electron microscopy (FE-SEM) has allowed to investigate the morphological evolution of the MOF as a function of operative parameters. Additionally, thermal analyses (TGA and DSC) have assessed the thermal stability and structural modifications of the Y-BTC samples.

Merging the chemistry of metal–organic and polyoxometalate clusters to form enhanced photocatalytic materials

The synergistic combination of a zirconium metal–organic cluster and a Keggin type polyoxotungstate led to a chemically stable and photoactive porous material.

Sodalite Cd66-Cage-Based Metal-Organic Framework Constructed by Cd9 and Cd5 Metal-Organic Clusters.

A sodalite Cd66-cage-based metal-organic framework (MOF), namely, CPM-9S, has been constructed based on Cd9 and Cd5 metal-organic clusters (MOCs), which, to the best our knowledge, represents the first Cd-cage-based MOF that contains the highest-nuclear Cd-based MOC and the largest number of Cd2+ ions in a cage. The iodine adsorption performances in terms of the iodine adsorption capacity, adsorption isotherm, and adsorption kinetics, as well as the adsorption mechanism, have been further studied.

Nanoscale Probing of Surface Charges in Functional Copper‐Metal Organic Clusters by Kelvin Probe Force Microscopy for Field‐Effect Transistors

AbstractMetal–organic frameworks (MOFs) have recently attracted a great deal of attention especially as conceivable advanced gate dielectrics for next‐generation field‐effect transistors (FETs) and memory device applications. Dielectric surface charge retention mapping is essential for gauging the leakage current and threshold voltage stability. Due to a dearth of systematic real‐time surface charge probing of MOFs dielectrics, in this work, the nanoscale Kelvin probe force microscopy (KPFM) technique is employed for the contact potential difference (CPD) analysis of developed hybrid copper–metal–organic clusters (Cu‐MOCs)/Si systems. Films are synthesized through the sol‐gel process consisting of copper metal core linked with organic ligands. With 3V positive and negative DC bias, charge injection offset between positive and negative bias is observed to be ≈190 mV, indicating the intrinsic Fermi level alignment between KPFM tip and sample surface charges. The high‐resolution surface CPD mappings bring forth the white (≈98 mV) and black (≈−91 mV) contrast profiles with hole (5.09 × 1012 cm−2) and electron (4.74 × 1012 cm−2) charge densities. Also, the 17 h time‐lapse enables the holes and electrons CPD mapping diameter shrinkage by ≈32% and 46%, respectively. In furtherance, a conductive filament model for host‐guest proton‐assisted conduction with charge hopping through fixed/mobile ions is proposed.

Real-time time-dependent density functional theory implementation of electronic circular dichroism applied to nanoscale metal-organic clusters.

Electronic circular dichroism (ECD) is a powerful spectroscopy method for investigating chiral properties at the molecular level. ECD calculations with the commonly used linear-response time-dependent density functional theory (LR-TDDFT) framework can be prohibitively costly for large systems. To alleviate this problem, we present here an ECD implementation within the projector augmented-wave method in a real-time-propagation TDDFT framework in the open-source GPAW code. Our implementation supports both local atomic basis sets and real-space finite-difference representations of wave functions. We benchmark our implementation against an existing LR-TDDFT implementation in GPAW for small chiral molecules. We then demonstrate the efficiency of our local atomic basis set implementation for a large hybrid nanocluster and discuss the chiroptical properties of the cluster.

Selective Construction of Magic Hierarchical Metal–Organic Clusters on Surfaces

Magic organic clusters, representing well-defined zero-dimensional organic clusters with identical sizes and configurations, have received increased interests in recent years. Previously, the magic clusters were mainly stabilized through van der Waals force, C–H...π interaction, hydrogen bonding, dipole interaction, etc., which yet lack thermal stability and tunable electronic transport properties for potential applications. The introduction of metal adatoms into the organic systems would be an excellent choice for facilitating more stable magic clusters as the metal adatoms could serve as a nucleation center and help for clustering of organic ligands with increased stabilities. Considering the limited coordination number of metal species, it would be of great interest to introduce multilevel interactions besides metal–organic bonding, which may provide new avenues for controllable fabrication of more complicated and larger magic clusters. Herein, we have achieved the controllable fabrication of three distinct magic metal–organic clusters, especially two hierarchical ones with different sizes on the reconstructed Au(111) and unreconstructed Ag(111) surface. The key for various unprecedented magic hierarchical clusters here is the selection of the organic ligands with only one active carboxyl (−COOH) group which possesses bonding flexibility and diversity features after dehydrogenation but avoids the usual two-dimensional network of those containing more −COOH groups.

Novel Fe4-based metal-organic cluster-derived iron oxides/S,N dual-doped carbon hybrids for high-performance lithium storage.

Metal-organic frameworks (MOFs) have been extensively used in the fabrication of new advanced electrode materials for lithium ion batteries (LIBs). However, low-productivity and high-cost are some of the main challenges of MOF-derived electrodes. Herein, we report a simple solvothermal procedure to fabricate novel Fe4-based metal-organic clusters (Fe-MOCs) with their subsequent conversion to an S,N dual-doped carbon framework incorporating iron oxides under a N2 atmosphere (namely Fe2O3@Fe3O4-SNC). The as-prepared Fe2O3@Fe3O4-SNC composite, owing to the strong interaction between the dual-doped carbon and iron oxides, shows excellent lithium storage performance as an anode with high pseudocapacitance. Furthermore, DFT computational analyses confirm that the hybrid shows excellent adsorption ability with a low energy barrier due to strong electronic interactions between the iron oxides and S,N-doped carbon matrix. In addition, Fe2O3@Fe3O4-SNC-based LIB shows high energy and power densities at the full-cell level, confirming this synthesis strategy to be a promising approach towards MOC-derived electrode materials for their application in LIBs and beyond-lithium batteries.

Combining valproate and bipyridyl ligands to construct a 0D core-shell Zn5(μ3-OH)2 cluster and a 2D layered coordination network with a [Zn3(μ3-OH)]2 SBU.

Starting from the proposed zinc carboxylate cluster tetrakis(μ-2-propylpentanoato)dizinc(II), Zn2(μ2-valp)4 (I), of valproic acid, a branched short-chain fatty acid, and bipyridine ligands, two new mixed-ligand coordination compounds, namely, bis(2,2'-bipyridine)di-μ3-hydroxido-hexakis(μ-2-propylpentanoato)bis(2-propylpentanoato)pentazinc(II), [Zn5(C8H15O2)8(OH)2(C10H8N2)2] (II), and poly[[bis(μ-4,4'-bipyridine)di-μ3-hydroxido-octakis(μ-2-propylpentanoato)bis(2-propylpentanoato)hexazinc(II)] dimethylformamide disolvate], {[Zn6(C8H15O2)10(OH)2(C10H8N2)2]·2C3H7NO}n (III), were synthesized. Compound II is a core-shell-type zero-dimensional discrete Zn5(μ3-OH)2 metal-organic cluster with Zn ions in double-triangle arrangements that share one Zn ion coincident with an inversion centre. The cluster contains three crystallographically non-equivalent Zn ions exhibiting three different coordination geometries (tetrahedral, square pyramidal and octahedral). The cluster cores are well separated and embedded in a protective shell of the aliphatic branched short chains of valproate. As a result, there is no specific interaction between the discrete clusters. Conversely, compound III, a 2D layered coordination network with a secondary building unit (SBU), is formed by Zn6(μ3-OH)2 clusters exhibiting a chair-like hexagonal arrangement. This SBU is formed from two Zn3(μ3-OH) trimers related by inversion symmetry and connected by two syn-anti bridging carboxylate groups. Each SBU is connected by four 4,4'-bipyridine ligands producing a 63-hcb net topology. 2D coordination layers are sandwiched within layers of dimethylformamide molecules that do not interact strongly with the network due to the hydrophobic protection provided by the valproate ligands.