Metal Organic Layers Research Articles

Sequential Modifications of Metal-Organic Layer Nodes for Highly Efficient Photocatalyzed Hydrogen Atom Transfer.

Herein, we report the synthesis of a bifunctional photocatalyst, Zr-OTf-EY, through sequential modifications of metal cluster nodes in a metal-organic layer (MOL). With eosin Y and strong Lewis acids on the nodes, Zr-OTf-EY catalyzes cross-coupling reactions between various C-H compounds and electron-deficient alkenes or azodicarboxylate to afford C-C and C-N coupling products, with turnover numbers of up to 1980. In Zr-OTf-EY-catalyzed reactions, Lewis acid sites bind the alkenes or azodicarboxylate to increase their local concentrations and electron deficiency for enhanced radical additions, while EY is stabilized by site isolation on the MOL to afford a long-lived catalyst for hydrogen atom transfer. The proximity between photostable EY sites and Lewis acids on the nodes of Zr-OTf-EY enhances the catalytic efficiency by approximately 400 times over the homogeneous counterpart in the cross-coupling reactions.

Dimensional Reduction of Metal–Organic Frameworks for Enhanced Cryopreservation of Red Blood Cells

AbstractTo increase the red blood cell (RBC) cryopreservation efficiency by metal–organic frameworks (MOFs), a dimensional reduction approach has been proposed. Namely, 3D MOF nanoparticles are progressively reduced to 2D ultra‐thin metal–organic layers (MOLs). We found that 2D MOLs are beneficial for enhanced interactions of the interfacial hydrogen‐bonded water network and increased utilization of inner ordered structures, due to the higher surface‐to‐volume ratio. Specifically, a series of hafnium (Hf)‐based 2D MOLs with different thicknesses (monolayer to stacked multilayers) and densities of hydrogen bonding sites have been synthesized. Both ice recrystallization inhibition activity (IRI) and RBCs cryopreservation assay confirm the pronounced better IRI activity and excellent cell recovery efficiency (up to ≈63 % at a very low concentration of 0.7 mg mL−1) of thin‐layered Hf‐MOLs compared to their 3D counterparts, thereby verifying the dimensional reduction strategy to improved cryoprotectant behaviors.

Dimensional Reduction of Metal-Organic Frameworks for Enhanced Cryopreservation of Red Blood Cells.

To increase the red blood cell (RBC) cryopreservation efficiency by metal-organic frameworks (MOFs), a dimensional reduction approach has been proposed. Namely, 3D MOF nanoparticles are progressively reduced to 2D ultra-thin metal-organic layers (MOLs). We found that 2D MOLs are beneficial for enhanced interactions of the interfacial hydrogen-bonded water network and increased utilization of inner ordered structures, due to the higher surface-to-volume ratio. Specifically, a series of hafnium (Hf)-based 2D MOLs with different thicknesses (monolayer to stacked multilayers) and densities of hydrogen bonding sites have been synthesized. Both ice recrystallization inhibition activity (IRI) and RBCs cryopreservation assay confirm the pronounced better IRI activity and excellent cell recovery efficiency (up to ≈63 % at a very low concentration of 0.7 mg mL-1 ) of thin-layered Hf-MOLs compared to their 3D counterparts, thereby verifying the dimensional reduction strategy to improved cryoprotectant behaviors.

Off-Lattice Coarse-Grained Model of Surface-Confined Metal–Organic Architectures

An off-lattice model of self-assembling surface-confined metal–organic nanostructures (SMONs) comprising tripod molecules has been developed. The model considers the directionality and saturability of coordination bonding. To parametrize the model, density functional theory methods have been used. Self-assembly of the SMONs has been simulated with Metropolis Monte Carlo method in the canonical ensemble. In this paper, we investigate how the directionality of metal–linker bonding and the linker/metal ratio affect the self-assembly of SMONs containing metal centers with different coordination numbers: M(II), M(III), and M(IV). The directionality of coordination bonding is determined by the functional group of the linker molecule and is defined in the model as the angular diameter of the interaction shell. Regardless of the preferred coordination number of the metal center, even a small change in the angular diameter significantly affects the structure of the SMONs. Depending on the angular diameter and composition of the metal–organic layer, various structures can appear. Using our model, we have simulated the self-assembly of the random porous (or defected honeycomb) and triangular structures, the set of hexagonal phases, amorphous structures of different densities, and metal–organic chains. Relative thermal stabilities of clusters of the main structures have been studied. The model reproduces correctly the main SMONs observed by scanning tunneling microscopy.

Metal-Organic Layer Delivers 5-Aminolevulinic Acid and Porphyrin for Dual-Organelle-Targeted Photodynamic Therapy.

The efficacy of photodynamic therapy (PDT) depends on the subcellular localization of photosensitizers. Herein, we report a dual-organelle-targeted nanoparticle platform for enhanced PDT of cancer. By grafting 5-aminolevulinic acid (ALA) to a Hf12 -based nanoscale metal-organic layer (Hf-MOL) via carboxylate coordination, ALA/Hf-MOL enhanced ALA delivery and protoporphyrin IX (PpIX) synthesis in mitochondria, and trapped the Hf-MOL comprising 5,15-di-p-benzoatoporphyrin (DBP) photosensitizers in lysosomes. Light irradiation at 630 nm simultaneously excited PpIX and DBP to generate singlet oxygen and rapidly damage both mitochondria and lysosomes, leading to synergistic enhancement of the PDT efficacy. The dual-organelle-targeted ALA/Hf-MOL outperformed Hf-MOL in preclinical PDT studies, with a 2.7-fold lower half maximal inhibitory concentration in cytotoxicity assays in vitro and a 3-fold higher cure rate in a colon cancer model in vivo.

A Mixed Protonic-Electronic Conductor Base on the Host-Guest Architecture of 2D Metal-Organic Layers and Inorganic Layers.

The key to designing and fabricating highly efficient mixed protonic-electronic conductors materials (MPECs) is to integrate the mixed conductive active sites into a single structure, to break through the shortcomings of traditional physical blending. Herein, based on the host-guest interaction, an MPEC is consisted of 2D metal-organic layers and hydrogen-bonded inorganic layers by the assembly methods of layered intercalation. Noticeably, the 2D intercalated materials (≈1.3nm) exhibit the proton conductivity and electron conductivity, which are 2.02 × 10-5 and 3.84 × 10-4 S cm-1 at 100°C and 99% relative humidity, much higher than these of pure 2D metal-organic layers (>>1.0 × 10-10 and 2.01×10-8 S cm-1 ), respectively. Furthermore, combining accurate structural information and theoretical calculations reveals that the inserted hydrogen-bonded inorganic layers provide the proton source and a networks of hydrogen-bonds leading to efficient proton transport, meanwhile reducing the bandgap of hybrid architecture and increasing the band electron delocalization of the metal-organic layer to greatly elevate the electron transport of intrinsic 2D metal-organic frameworks.

Spin Manipulation in a Metal–Organic Layer through Mechanical Exfoliation for Highly Selective CO2Photoreduction

AbstractSpin manipulation of transition‐metal catalysts has great potential in mimicking enzyme electronic structures to improve activity and/or selectivity. However, it remains a great challenge to manipulate room‐temperature spin state of catalytic centers. Herein, we report a mechanical exfoliation strategy to in situ induce partial spin crossover from high‐spin (s=5/2) to low‐spin (s=1/2) of the ferric center. Due to spin transition of catalytic center, mixed‐spin catalyst exhibits a high CO yield of 19.7 mmol g−1with selectivity of 91.6 %, much superior to that of high‐spin bulk counterpart (50 % selectivity). Density functional theory calculations reveal that low‐spin 3d‐orbital electronic configuration performs a key function in promoting CO2adsorption and reducing activation barrier. Hence, the spin manipulation highlights a new insight into designing highly efficient biomimetic catalysts via optimizing spin state.

Spin Manipulation in a Metal-Organic Layer through Mechanical Exfoliation for Highly Selective CO2 Photoreduction.

Spin manipulation of transition-metal catalysts has great potential in mimicking enzyme electronic structures to improve activity and/or selectivity. However, it remains a great challenge to manipulate room-temperature spin state of catalytic centers. Herein, we report a mechanical exfoliation strategy to in situ induce partial spin crossover from high-spin (s=5/2) to low-spin (s=1/2) of the ferric center. Due to spin transition of catalytic center, mixed-spin catalyst exhibits a high CO yield of 19.7 mmol g-1 with selectivity of 91.6 %, much superior to that of high-spin bulk counterpart (50 % selectivity). Density functional theory calculations reveal that low-spin 3d-orbital electronic configuration performs a key function in promoting CO2 adsorption and reducing activation barrier. Hence, the spin manipulation highlights a new insight into designing highly efficient biomimetic catalysts via optimizing spin state.

2D Nano-Sonosensitizers Facilitate Energy Transfer to Enhance Sonodynamic Therapy.

Although sonodynamic therapy (SDT) has shown promise for cancer treatment, the lack of efficient sonosensitizers (SSs) has limited the clinical application of SDT. Here, a new strategy is reported for designing efficient nano-sonosensitizers based on 2D nanoscale metal-organic layers (MOLs). Composed of Hf-oxo secondary building units (SBUs) and iridium-based linkers, the MOL is anchored with 5,10,15,20-tetra(p-benzoato)porphyrin (TBP) sensitizers on the SBUs to afford TBP@MOL. TBP@MOL shows 14.1- and 7.4-fold higher singlet oxygen (1 O2 ) generation than free TBP ligands and Hf-TBP, a 3D nanoscale metal-organic framework, respectively. The 1 O2 generation of TBP@MOL is enhanced by isolating TBP SSs on the SBUs of the MOL, which preventsaggregation-induced quenching of the excited sensitizers, and by triplet-triplet Dexter energy transfer between excited iridium-based linkers and TBP SSs, which more efficiently harnesses broad-spectrum sonoluminescence. Anchoring TBP on the MOL surface also enhances the energy transfer between the excited sensitizer and ground-state triplet oxygen to increase 1 O2 generation efficacy. In mouse models of colorectal and breast cancer, TBP@MOL demonstrates significantly higher SDT efficacy than Hf-TBP and TBP. This work uncovers a new strategy to design effective nano-sonosensitizers by facilitating energy transfer to efficiently capture broad-spectrum sonoluminescence and enhance 1 O2 generation.

Molecular Engineering of Metal-Organic Layers for Sustainable Tandem and Synergistic Photocatalysis.

Metal-organic layers (MOLs), a monolayered version of metal-organic frameworks (MOFs), have recently emerged as a novel two-dimensional molecular material platform to design multifunctional catalysts. MOLs inherit the intrinsic molecular tunability of MOFs and yet have more accessible and modifiable building blocks. Here we report molecular engineering of six MOLs via modulated solvothermal synthesis between HfCl4 and three photosensitizing ligands followed by postsynthetic modification with two carboxylate-containing cobaloximes for tandem and synergistic photocatalysis. Morphological and structural characterization by transmission electron microscopy and atomic force microscopy and compositional analysis by inductively coupled plasma-mass spectrometry and nuclear magnetic resonance spectroscopy establish the MOLs as flat nanoplates with a periodic lattice structure of hexagonal symmetry. The MOLs efficiently catalyze tandem dehydrogenative coupling reactions and synergistic Heck-type coupling reactions. The most active MOL catalyst was used for the gram-scale synthesis of vesnarinone, a cardiotonic agent, in 80% yield with a turnover number of 400 and in eight consecutive reaction cycles without significant loss of activities.

Metal-organic layers: Preparation and applications

Metal-organic layers (MOLs) have attracted considerable interest in materials science because of their unique characteristics. The past decade has witnessed the rapid development of MOLs in synthesis and applications. Here we present a review of the latest research advances on MOLs. First, we introduce the two preparation approaches for MOLs, namely, the top-down and bottom-up approaches. Then, we discuss the applications of MOLs in gas separation, catalysis, energy catalysis and conversion, and chemical sensors, which emphasize the performance-morphologies/structures relationship of MOLs. At the end of this review, we provide an outlook on the opportunities and challenges of MOLs in the future.

Porphyrin-Moiety-Functionalized Metal–Organic Layers Exhibiting Catalytic Capabilities for Detoxifying Nerve Agent and Blister Agent Simulants

The development of very efficient bifunctional catalysts for the simultaneous detoxification of two kinds of the deadliest chemical warfare agents (CWAs), nerve agent and blister agent, is highly desirable. In this study, two porphyrin-based ligands [tetrakis(4-carboxyphenyl) porphyrin (TCPP) and protoporphyrin IX (PPIX)] are introduced into 2D Zr-1,3,5-tris(4-carboxyphenyl)benzene (BTB) metal-organic layers (MOLs), composed of six-connected Zr6 nodes and the tritopic carboxylate ligand BTB, by a solvent-assisted ligand incorporation method. The loads of TCPP and PPIX are 6.4 and 10.9 wt %, respectively. The detoxification of simulants of the nerve agent and the blister agent was conducted to investigate the catalytic activity of porphyrin-moiety-functionalized MOLs. The reaction half-life of optimal TCPP-functionalized MOL catalyzing the hydrolysis of a nerve agent simulant is only 2.8 min, meanwhile, the half-life of the selective catalytic oxidation of a blister agent simulant is only 1.2 min under LED illumination. More importantly, such a degradation half-life is only about 4 min under natural sunlight (∼60 mW/cm2). To our knowledge, TCPP-functionalized MOL is by far the most efficient catalyst for blister agent simulant degradation under solar light. Therefore, 2D ultrathin MOLs on demand appear to be a promising and efficient material platform for the development of bifunctional catalysts for CWA protection.

Construction of Sb-capped Dawson-type POM derivatives for high-performance asymmetric supercapacitors

Modified polyoxometalate (POM) derivatives are promising pseudocapacitive active materials due to their abundant active sites and high redox capacity. Here, we constructed four antimony-capped Dawson-type molybdate clusters with high specific capacitance properties for the first time through the traditional hydrothermal method, formulated as [Cu(im)2]4{[Cu2(im)2]1/2(im)}[H3/2(Sb1Sb1/3Sb2/3)P2Mo7VMo11VIO62]·H2O (1); [Cu(bzim)2][H4Sb1Sb1/2 × 2P2Mo7VMo11VIO62]·(bzim)4·2H3O (2); [(bzim)4(NO3)1/2][H5/2Sb2P2Mo3VMo15VIO62]·H3O (3); [(bzim)4(bzim)1/3][HSb2P2Mo2VMo16VIO62]·H3O (4) (im= imidazole, bzim= benzimidazole). The compounds 1–4 all contain Sb-capped Dawson type {P2Mo18} anions with 3D supramolecular channel structures. Especially, compound 1 expresses a porous 2D metal-organic layer formed by Cu-ims transition metal complexes (TMCs) through the Cu-O interaction, and Sb capped-polyanions are exactly filled in the holes. Importantly, compound 1 exhibits a higher specific capacitance (Cs) value of 1401.75 F g−1 than the other three compounds (1141 F g−1, 1027.3 F g−1, and 978.25 F g−1) at a current density of 1.4 A g−1. In addition, the asymmetric supercapacitor Sb-P2Mo18//AC assembled with compound 1 and active carbon exhibits good cycling stability (89.14 %), and possesses an excellent energy density of 17.78 W h Kg−1, which could be attributed to the high redox capacity and excellent electronic conductivity. The experimental results demonstrate the feasibility of the synthesis strategy and pave the way for exploring novel high-performance polyoxometalate-based pseudocapacitive materials.

Phosphine-based metal-organic layers to construct single-site heterogeneous catalysts for arene borylation.

Metal-organic layers (MOLs) are versatile platforms for creating single-site heterogeneous catalysts. Incorporating molecular functionalities into MOLs is crucial for catalysis. In this study, we synthesized phosphine-containing MOLs constructed from Hf6-oxo secondary building units (SBUs) and phosphine ligands. The mono(phosphine)-Ir complexes generated by the metalation of TPP-MOL were highly active as heterogeneous catalysts for the C(sp2)-H borylation of a range of arenes. This research expands the diversity of MOL-based catalysts.

Structural engineering of metal–organic layers toward stable Li–CO2 batteries

A flower-like metal–organic layer with a rich catalytic surface and unique conductive structure was fabricated as an efficient cathodic catalyst for Li–CO2 batteries. The as-developed cells display remarkable cycling stability.

Metal organic layers enabled cell surface engineering coupling biomembrane fusion for dynamic membrane proteome profiling.

Systematically dissecting the highly dynamic and tightly communicating membrane proteome of living cells is essential for the system-level understanding of fundamental cellular processes and intricate relationship between membrane-bound organelles constructed through membrane traffic. While extensive efforts have been made to enrich membrane proteins, their comprehensive analysis with high selectivity and deep coverage remains a challenge, especially at the living cell state. To address this problem, we developed the cell surface engineering coupling biomembrane fusion method to map the whole membrane proteome from the plasma membrane to various organelle membranes taking advantage of the exquisite interaction between two-dimensional metal-organic layers and phospholipid bilayers on the membrane. This approach, which bypassed conventional biochemical fractionation and ultracentrifugation, facilitated the enrichment of membrane proteins in their native phospholipid bilayer environment, helping to map the membrane proteome with a specificity of 77% and realizing the deep coverage of the HeLa membrane proteome (5087 membrane proteins). Furthermore, membrane N-phosphoproteome was profiled by integrating the N-phosphoproteome analysis strategy, and the dynamic membrane proteome during apoptosis was deciphered in combination with quantitative proteomics. The features of membrane protein N-phosphorylation modifications and many differential proteins during apoptosis associated with mitochondrial dynamics and ER homeostasis were found. The method provided a simple and robust strategy for efficient analysis of membrane proteome, offered a reliable platform for research on membrane-related cell dynamic events and expanded the application of metal-organic layers.

A 2D Dy-based metal-organic framework derived from benzothiadiazole: structure and photocatalytic properties.

A 2D Dy(III) metal-organic layer (MOL 1) was synthesized under solvothermal conditions. Structural analysis suggests that the Dy(III) ions in each one-dimensional (1D) arrangement are evenly arranged in the form of broken lines. The 1D chains are linked to one another via ligands to form a 2D layer that generates a 2D surface with elongated apertures. The photocatalytic activity study suggests that MOL 1 exhibits good catalytic activity in flavonoids by the formation of an O2˙- radical as an intermediate. This is the first reported method of synthesizing flavonoids using chalcones.

Ultrathin metal−organic layers/carbon nitride nanosheet composites as 2D/2D heterojunctions for efficient CO2 photoreduction

Metal−organic layers (MOLs), with well-defined, abundant active sites and good electron transport capabilities, are ideal platforms for studying the photoreduction of CO2 to value-added chemicals feedstocks in 2D/2D assembled materials.

Simple lattice model of surface-confined metal–organic networks consisting of linear nitrogen-bearing molecules and transition metals

How do the size of nitrogen-bearing groups of the linker-molecule and the type of the coordinating metal center affect the phase behavior and thermal stability of surface-confined metal–organic layers?

Electrochemical Enzyme Sensor Based on the Two-Dimensional Metal–Organic Layers Supported Horseradish Peroxidase

Metal-organic frames (MOFs) have recently been used to support redox enzymes for highly sensitive and selective chemical sensors for small biomolecules such as oxygen (O2), hydrogen peroxide (H2O2), etc. However, most MOFs are insulative and their three-dimensional (3D) porous structures hinder the electron transfer pathway between the current collector and the redox enzyme molecules. In order to facilitate electron transfer, here we adopt two-dimensional (2D) metal-organic layers (MOLs) to support the HRP molecules in the detection of H2O2. The correlation between the current response and the H2O2 concentration presents a linear range from 7.5 μM to 1500 μM with a detection limit of 0.87 μM (S/N = 3). The sensitivity, reproducibility, and stability of the enzyme sensor are promoted due to the facilitated electron transfer.