Metal Organic Layers Research Articles

A three-dimensional octamolybdate-modified silver crystalline material with catalytic and antibacterial activities

The hydrothermal reaction of 1-(4-carboxyphenyl)-3-(pyrazine-2-yl)-pyrazole (HX) with AgNO3 in the presence of [PMo12O40]3− anions results in a new 3D octamolybdate-based metal–organic complex, [Ag2(HX)(X)(H2Mo8O26)0.5]·H2O (1). 1 was characterized using X-ray photoelectron spectra, scanning electron microscopy, powder X-ray diffraction, elemental mapping, IR spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. In compound 1, [H2Mo8O26]2− was in situ generated from the Keggin-type [PMo12O40]3−. Compound 1 is a 3D framework composed of 2D metal–organic layers [Ag2(HX)(X)]nn+ and [H2Mo8O26]2− clusters. Its electrochemical properties were investigated and the results showed that 1 could serve as an electrochemical sensor to detect NO2−. Compound 1 exhibits photocatalytic activity in the degradation of methylene blue, methyl orange and Rhodamine B. The mechanism of the photocatalytic degradation was also studied. Additionally, the antibacterial properties against Escherichia coli, Ralstonia solanacearum and Xanthomonas axonopodis pv. Citri were investigated.

Tailoring rhodium-based metal-organic layers for parahydrogen-induced polarization: achieving 20% polarization of 1H in liquid phase

Abstract Heterogeneous catalysts for parahydrogen-induced polarization (HET-PHIP) would be useful for producing high sensitivity contrasting agents for magnetic resonance imaging (MRI) in liquid phase, as they can be removed by simple filtration. Although homogeneous hydrogenation catalysts are highly efficient for PHIP, their sensitivity decreases when anchored on porous supports due to slow substrate diffusion to the active sites and rapid depolarization within the channels. To address this challenge, we explored two-dimensional (2D) metal-organic layers (MOLs) as supports for active Rh complexes with diverse phosphine ligands and tunable hydrogenation activities, taking advantage of accessible active sites and chemical adaptability of the MOLs. By adjusting the electronic properties of phosphines, TPP-MOL-Rh-dppb (TPP = tris(4-carboxylphenyl)phosphine), featuring a κ2-connected di(phosphine) ligand, generated hyperpolarized styrene achieving over 2400-fold signal enhancement and polarization level of 20% for 1H in methanol-d4 solution. The TPP-MOL-Rh-dppb effectively inherited the high efficiency and pairwise addition of its homogenous catalyst while maintaining the heterogeneity of MOL. This work demonstrates the potential of 2D phosphine-functionalized MOLs as heterogenous solid support for HET-PHIP.

Cationic Metal-Organic Layer Delivers siRNAs to Overcome Radioresistance and Potentiate Cancer Radiotherapy.

Radiotherapy plays an important role in modern oncology, but its treatment efficacy is limited by the radioresistance of tumor cells. As a member of the inhibitor of apoptosis protein family, survivin plays a key role in developing radioresistance by mediating apoptosis evasion, promoting epithelial-mesenchymal transition, and modulating cell cycle dynamics. Efficient downregulation of survivin expression presents a promising strategy to enhance the antitumor effects of radiotherapy. Herein, we report the design of a hafnium-porphyrin-based cationic metal-organic layer (CMOL) with quaternary ammonium capping groups to deliver small interfering RNAs (siRNAs) for enhanced radiotherapy. The CMOL@siRNA nanoplatform not only increased energy deposition from X-rays and reactive oxygen species generation via a unique radiotherapy-radiodynamic therapy process, but also effectively delivered siRNAs to downregulate survivin expression and ameliorate radioresistance of cancer cells. Consequently, CMOL@siRNA in combination with low-dose X-ray irradiation demonstrated remarkable antitumor efficacy with 96.9% and 91.4% tumor growth inhibition in murine colorectal carcinoma and triple-negative breast cancer models, respectively.

Structurally Asymmetric Ni-O-Mn Node in Metal-Organic Layers on Carbon Nitride Support for CO2 Photoreduction.

The Jahn-Teller (J-T) effect-induced lattice distortion presents an advantageous approach to tailor the electronic structure and CO2 adsorption properties of catalytic centers, consequently conferring desirable photocatalytic CO2 reduction activity and selectivity. Nevertheless, achieving precise J-T distortion control over catalytic sites to enhance CO2 adsorption/activation and target-product desorption remains a formidable challenge. In this work, we successfully induced J-T lattice distortion in neighboring Ni sites by exchanging high-spin Mn2+ into Ni-O-Ni nodes. EXAFS results and DFT simulations revealed that the highly asymmetric Ni-O-Mn nodes induced structural contraction (shortened Ni-O bonds) in the adjacent Ni-O lattice. The magnetic hysteresis loop (M-H) confirmed that the introduction of Mn2+ increased the number of spin electrons, thereby increasing the magnetization intensity. The spin mismatch between photogenerated electrons and holes suppressed charge recombination. Significantly, the d orbitals of the Ni sites in the Ni-O-Mn nodes exhibited strong orbital hybridization with the p orbitals of CO2, as evidenced by the enhanced d-p orbital overlap, facilitating rapid CO2 adsorption and activation. Consequently, the sample featuring lattice-mismatched Ni-O-Mn nodes exhibited an 8.79-fold enhancement in CO production rate compared to the Ni-O-Ni nodes, in the absence of cocatalysts and sacrificial reagents.

Bifunctional Metal–Organic Layer for Selective Photocatalytic Carbon Dioxide Reduction to Carbon Monoxide

Bifunctional Metal–Organic Layer for Selective Photocatalytic Carbon Dioxide Reduction to Carbon Monoxide

Polyoxometalate-embedded copper-organic network as dual-site synergetic catalyst for the selective oxidation of benzylic C−H bond

Selective activation and oxidization of inert C−H bonds into value-added chemicals affords attractively economic and ecological benefits, as well as central challenge in modern synthetic chemistry. Herein, by integrating the redox polyoxometalate (POM) centers and multinuclear copper sites in one system, four compounds were constructed with formulas of [Cu2(μ2-Cl)(H2O)2L3][PM12O40]·4H2O (M = Mo for 1, W for 2), and [Cu4(μ2-OH)4L2] [H3PM11CuO40]·12H2O (M = Mo for 3, W for 4, L = 1,4-di[4H-1,2,4-triazol-4-yl]-benzene). Both compounds 1–2 exhibited 3-D POM-embedded supramolecular networks constructed by discrete [PM12O40]3− clusters and binuclear {Cu2(μ2-Cl)(N–N)2} unit-based metal-organic sheets. While compounds 3–4 displayed 3-D POM-supported supramolecular networks composed of monosubstituted Keggin-type anions [H3PM11CuO40]4− and {Cu2(μ2-OH)(N–N)2} chain-based metal-organic layers. Four crystalline structures with distinct dual-active site distribution showed significant peroxidase-like activities owing to the collaborative catalysis of multinuclear copper units and polyanionic clusters, which can smoothly catalyze the C−H bond oxidation of diphenylmethane to benzophenone with ca. 97 % conversion and >98 % selectivity within 24 h. Notably, the monosubstituted [H3PM11CuO40]4−-based compounds 3−4 showed higher catalytic activities than [PM12O40]3−-based compounds 1−2 (88 % conversion and >97 % selectivity within 12 h). This kind of crystalline structures also showed good recoverability. The synergetic reaction mechanism was also explored. This work provides a new strategy to design robust heterogeneous POM-based synergetic catalysts for C−H bond functionalization.

Synergistic Coordination and Surface Plasmon Resonance of Quantum Dots in Enhancing Photocatalytic Hydrogen Evolution.

Recent studies have revealed that the integration of metal nanoparticles (NPs) with photocatalysts allows the metal NPs to serve as cocatalysts, significantly enhancing reactant efficiency near nanostructures through the surface plasmon resonance (SPR) effect. On this basis, we synthesized highly reactive FePt quantum dots (FePt QDs) with tailored configurations, manipulating the Pt coordination environment and combining FePt QDs with ultrathin two-dimensional nickel metal-organic layer (Ni-MOL) nanosheets. X-ray absorption fine spectroscopy (XAFS) confirmed the distinctive Pt-Fe configuration after photoactivation. The optimized loading amount of FePt QDs led to a hydrogen evolution reaction (HER) yield of 113 mmol·g-1·h-1 after activation, with the catalyst remaining stable over five cycles. The improved reaction efficiency stemmed from Pt coordination adjustments and a localized SPR effect, supported by ultraviolet-visible (UV-vis), infrared (IR), Raman, and XAFS characterizations. A comparative analysis was conducted with Ni-MOL deposited with platinum NPs, further underscoring the distinct advantages of FePt QDs and corroborating by density functional theory (DFT) calculations, which revealed favorable d-band center properties. These findings offer a promising avenue for the development of highly efficient and stable nanoalloy photocatalysts.

Integration of metal-organic layers with quantum dots for artificial photosynthesis

Integration of metal-organic layers with quantum dots for artificial photosynthesis

Superhydrophobic metal-organic framework layers as multifunctional ion-conducting interfaces for ultra-stable Zn anodes

Aqueous zinc batteries (AZBs) show great promise for cost-effective, high-safety, and large-scale energy storage. Yet, corrosion and dendrite formation at the Zn anode interface undermine its stability, shortening the cycle life. In this work, a fluorosilane-modified metal-organic framework layer (F-MOF) is successfully prepared as a multifunctional ion-conductive interface to stabilize the Zn anode. The designed MOF-based artificial layer provides a uniform pathway for Zn deposition, while its hydrophobic nature prevents negative effects such as hydrogen evolution and corrosion. According to density functional theory (DFT) calculations, the hydration energy of Zn2+ in F-MOF@Zn(002) is reduced while the adsorption energy for Zn2+ is increased. This facilitates the desolvation process on the Zn anode surface, promoting uniform Zn deposition. Consequently, the lifespan of the F-MOF-coated Zn anode extends beyond 2000 h at a current density of 1 mA cm−2 (areal capacity: 0.5 mAh cm−2), significantly outlasting both bare Zn (225 h) and MOF-coated Zn (751 h) anodes. Additionally, the assembled coin cells and pouch-type full cells prove the practical availability of F-MOF@Zn anodes for AZBs. The F-MOF@Zn//MnO2 full cell maintains a high-capacity retention exceeding 91.9 % even after 1000 cycles. This work highlights the practical application potential of hydrophobic MOF coatings for AZBs.

Isomeric organic ligands directing octamolybdates-linked Copper(II) functionalized complexes as active catalysts in electrochemistry and desulfurization

Two remarkable octamolybdates-based copper-organic complexes, namely, [Cu7(L)4(H2O)7(β-H2Mo8O26)]·7H2O (POM 1) and [Cu6(HX)4(β-Mo8O26)(H2O)6]·3H2O (POM 2) (H3L = 2-(pyridine-4-yl)-1H-imidazole-4,5-dicarboxylic acid; H3X = 2-(pyridine-3-yl)-1H-imidazole-4,5-dicarboxylic acid), were successfully assembled using two isomeric organic ligands under hydrothermal conditions. The two-dimensional metal-organic layers of POMs 1 and 2 were converted into three-dimensional frameworks by hexadentate β-H2Mo8O262− and tetradentate β-Mo8O264− clusters, respectively. The electrocatalytic properties of POM 1 were investigated, revealing its ability to catalyze the reduction of BrO3−, NO2− and H2O2 and the oxidation of ascorbic acid. Notably, POMs 1 and 2 demonstrated exceptional stability in organic solvents and exhibited excellent catalytic performance in oxidative desulfurization. When employed as catalysts for thioanisole oxidation, the conversion rates reached 94.5% after 150 min for POMs 1 and 99.9% after 120 min for POMs 2. In addition, their catalytic performances in model oil remained largely unchanged after five recycling cycles.

Modulating the zinc ion flux and electric field intensity by multifunctional metal-organic complex interface layer for highly stable Zn anode

The uncontrollable growth of Zn dendrites accompanied by side reactions severely impedes the industrialized process of zinc ion electrochemical energy storage devices. Herein, we propose a practical metal-organic complex interface layer to manipulate the zinc ion flux and electric field intensity, enabling highly homogeneous zinc electrodeposition. The zinc-terephthalic acid complex (ZnPTA) with lower adsorption energy for zinc ion (−1.3 eV) builds a zincophilic interface favoring the ordered nucleation and growth of Zn. Moreover, the ZnPTA layer can serve as physical barrier to protect the newly deposited Zn from corrosion in the aqueous electrolyte. The modified Zn anode with the ZnPTA layer (ZnPTA@Zn) demonstrates excellent cycling stability more than 3000 h at 1 mA/cm2. Besides, the zinc-ion battery and zinc-ion hybrid capacitor using the ZnPTA@Zn electrode deliver outstanding cycle performance (up to 5500 cycles with high residual capacity ratio of 77.9%). This work provides a promising metal-organic complex interface design on enhancing the performance of Zn metal anode.

Nanoscale Metal-Organic Layer Reprograms Cellular Metabolism to Enhance Photodynamic Therapy and Antitumor Immunity.

Abnormal cancer metabolism causes hypoxic and immunosuppressive tumor microenvironment (TME), which limits the antitumor efficacy of photodynamic therapy (PDT). Herein, we report a photosensitizing nanoscale metal-organic layer (MOL) with anchored 3-bromopyruvate (BrP), BrP@MOL, as a metabolic reprogramming agent to enhance PDT and antitumor immunity. BrP@MOL inhibited mitochondrial respiration and glycolysis to oxygenate tumors and reduce lactate production. This metabolic reprogramming enhanced reactive oxygen species generation during PDT and reshaped the immunosuppressive TME to enhance antitumor immunity. BrP@MOL-mediated PDT inhibited tumor growth by >90 % with 40 % of mice being tumor-free, rejected tumor re-challenge, and prevented lung metastasis. Further combination with immune checkpoint blockade potently regressed the tumors with >98 % tumor inhibition and 80 % of mice being tumor-free.

Nanoscale Metal‐Organic Layer Reprograms Cellular Metabolism to Enhance Photodynamic Therapy and Antitumor Immunity

AbstractAbnormal cancer metabolism causes hypoxic and immunosuppressive tumor microenvironment (TME), which limits the antitumor efficacy of photodynamic therapy (PDT). Herein, we report a photosensitizing nanoscale metal–organic layer (MOL) with anchored 3‐bromopyruvate (BrP), BrP@MOL, as a metabolic reprogramming agent to enhance PDT and antitumor immunity. BrP@MOL inhibited mitochondrial respiration and glycolysis to oxygenate tumors and reduce lactate production. This metabolic reprogramming enhanced reactive oxygen species generation during PDT and reshaped the immunosuppressive TME to enhance antitumor immunity. BrP@MOL‐mediated PDT inhibited tumor growth by >90 % with 40 % of mice being tumor‐free, rejected tumor re‐challenge, and prevented lung metastasis. Further combination with immune checkpoint blockade potently regressed the tumors with >98 % tumor inhibition and 80 % of mice being tumor‐free.

A Stable Site‐Isolated Mono(phosphine)‐Rhodium Catalyst on a Metal‐Organic Layer for Highly Efficient Hydrogenation Reactions

AbstractPhosphine‐ligated transition metal complexes play a pivotal role in modern catalysis, but our understanding of the impact of ligand counts on the catalysis performance of the metal center is limited. Here we report the synthesis of a low‐coordinate mono(phosphine)‐Rh catalyst on a metal‐organic layer (MOL), P‐MOL • Rh, and its applications in the hydrogenation of mono‐, di‐, and tri‐substituted alkenes as well as aryl nitriles with turnover numbers (TONs) of up to 390000. Mechanistic investigations and density functional theory calculations revealed the lowering of reaction energy barriers by the low steric hindrance of site‐isolated mono(phosphine)‐Rh sites on the MOL to provide superior catalytic activity over homogeneous Rh catalysts. The MOL also prevents catalyst deactivation to enable recycle and reuse of P‐MOL • Rh in catalytic hydrogenation reactions.

A Stable Site-Isolated Mono(phosphine)-Rhodium Catalyst on a Metal-Organic Layer for Highly Efficient Hydrogenation Reactions.

Phosphine-ligated transition metal complexes play a pivotal role in modern catalysis, but our understanding of the impact of ligand counts on the catalysis performance of the metal center is limited. Here we report the synthesis of a low-coordinate mono(phosphine)-Rh catalyst on a metal-organic layer (MOL), P-MOL • Rh, and its applications in the hydrogenation of mono-, di-, and tri-substituted alkenes as well as aryl nitriles with turnover numbers (TONs) of up to 390000. Mechanistic investigations and density functional theory calculations revealed the lowering of reaction energy barriers by the low steric hindrance of site-isolated mono(phosphine)-Rh sites on the MOL to provide superior catalytic activity over homogeneous Rh catalysts. The MOL also prevents catalyst deactivation to enable recycle and reuse of P-MOL • Rh in catalytic hydrogenation reactions.

Chemoenzymatic Catalysts Immobilized on Metal–Organic Layers for the Asymmetric Reduction of Unreactive Stereoisomers of Alkenes

Chemoenzymatic Catalysts Immobilized on Metal–Organic Layers for the Asymmetric Reduction of Unreactive Stereoisomers of Alkenes

Pyrenetetrasulfonate-grafted 2D ultrathin metal–organic layer as new electrochemiluminescence emitters for ultrasensitive microRNA-21 assay

The exploration of novel electrochemiluminescence (ECL) luminophores with excellent ECL properties is a current research hotspot in the ECL field. Herein, a novel high-efficiency Ru-complex-free ECL emitter PyTS-Zr-BTB-MOL has been prepared by using porous ultrathin Zr-BTB metal–organic layer (MOL) as carrier to coordinatively graft the cheap and easily available polycyclic aromatic hydrocarbon (PAH) derivative luminophore PyTS whose ECL performance has never been investigated. Gratifyingly, the ECL intensity and efficiency of PyTS-Zr-BTB-MOL were markedly enhanced compared to both PyTS monomers and PyTS aggregates. The main reason was that the distance between pyrene rings was greatly expanded after the PyTS grafting on the Zr6 clusters of Zr-BTB-MOL, which overcame the aggregation-caused quenching (ACQ) effect of PyTS and thus enhanced the ECL emission. Meanwhile, the porous nanosheet structure of PyTS-Zr-BTB-MOL could distinctly increase the exposure of PyTS luminophores and shorten the diffusion paths of coreactants and electrons/ions, which effectively promoted the electrochemical excitation of more PyTS luminophores and thus achieved a further ECL enhancement. In light of the remarkable ECL property of PyTS-Zr-BTB-MOL, it was employed as an ECL indicator to build a novel high-sensitivity ECL biosensor for microRNA-21 determination, possessing a satisfactory response range (100 aM to 100 pM) and an ultralow detection limit (10.4 aM). Overall, this work demonstrated that using MOLs to coordinatively graft the PAH derivative luminophores to eliminate the ACQ effect and increase the utilization rate of the luminophores is a promising and efficient strategy to develop high-performance Ru-complex-free ECL materials for assembling ultrasensitive ECL biosensing platforms.

Understanding the passivation layer formed by tolyltriazole on copper, bronze, and brass surfaces

Tolyltriazole (TTAH) is used industrially as a corrosion inhibitor for copper alloys, particularly in organic media. In this study, the morphology and chemistry of the layer formed by TTAH on copper and copper alloys under realistic conditions is investigated, with focus on the effects due to the presence of tin or zinc in the substrates. A combination of X-ray photoelectron spectroscopy (XPS), medium energy ion scattering (MEIS), and scanning transmission electron microscopy (STEM) has been used. It was found that an inhomogeneous metal–organic layer forms on the surface of copper specimens, likely in the form of copper nanoparticles surrounded by CuxTTAy complexes. This layer increases in thickness for at least 30 days. Chemically, the copper species in the layer are initially in the +2 oxidation state, but after longer exposure to TTAH, mostly Cu(I) is observed. In bronze samples, tin does not appear to segregate to the surface layer. In brass samples, zinc is depleted from the bulk and forms a thicker ZnxTTAy layer.

Next-generation of a Fe-Ce double variable-valence metals modulated high-efficiency nanozyme

High catalytic efficiency is the continuous pursuit for the preparation of high-performance nanozymes. In this work, a Fe-Ce double variable-valence metals nanozyme (Fe-Ce-MOL) was constructed based on metal–organic layers (MOLs), a class of two-dimensional metal–organic frameworks with ultra-thin structure, for peroxidase (POD) mimicking. Fe-Ce-MOL exhibited significantly enhanced catalytic activity in comparison with that of natural horseradish peroxidase and single variable-valence metal nanozyme (Fe-Zr-MOL). Density functional theory calculations demonstrated that the Fe site of Fe-Ce-MOL had a stronger adsorption effect on H2O2 compared to Fe-Zr-MOL and more heat was released in the catalytic reaction of H2O2, making the reaction easier to occur. Moreover, there was more electron transfer between Fe and Ce double variable-valence metals, also accelerating the catalytic process. These results indicated that the ultra-thin structure of Fe-Ce-MOL provided more catalytic sites and Fe and Ce double variable-valence metals could regulate the process of oxidation–reduction and promote the efficiency of electron transfer synergistically. As a proof of concept, the proposed Fe-Ce-MOL was used in biosensing and antibacterial applications. These results suggested that Fe-Ce-MOL had great potential as a new-generation nanozyme. This work pioneers a new approach for the rational design of highly efficient nanozymes.

Defect-Induced All-Solid-State Frustrated Lewis Pair on Metal-Organic Monolayer Accelerating Photocatalytic CO2 Reduction with H2O Vapor.

Understanding the structure-performance relationships of a frustrated Lewis pair (FLP) at the atomic level is key to yielding high efficiency in activating chemically "inert" molecules into value-added products. A sound strategy was developed herein through incorporating oxygen defects into a Zr-based metal-organic layer (Zr-MOL-D) and employing Lewis basic proximal surface hydroxyls for the in situ formation of solid heterogeneous FLP (Zr4-δ-VO-Zr-OH). Zr-MOL-D exhibits a superior CO2 to CO conversion rate of 49.4 μmol g-1 h-1 in water vapor without any sacrificing agent or photosensitizer, which is about 12 times higher than that of pure MOL (Zr-MOL-P), with extreme stability even after being placed for half a year. Theoretical and experimental results reveal that the introduction of FLP converts the process of the crucial intermediate COOH* from an endothermic reaction to an exothermic spontaneous reaction. This work is expected to provide new prospects for developing efficient MOL-based photocatalysts in FLP chemistry through a sound defect-engineering strategy.