2D Metal Organic Framework Nanosheet: A Universal Platform Promoting Highly Efficient Visible‐Light‐Induced Hydrogen Production

2D metal–organic frameworks and their derivatives for the oxygen evolution reaction

Two-Dimensional Metal–Organic Frameworks with Unique Oriented Layers for Oxygen Reduction Reaction: Tailoring the Activity through Exposed Crystal Facets

On-surface fabrication of two-dimensional (2D) metal organic frameworks (MOFs) has been continuously attracting attentions for years. However, the synthesis of 2D MOFs with large-amplitude flexibility was rarely carried out since the bonding configurations in the coordination nodes are typically highly directional. Here we demonstrate that single alkali ions, which are fully isotropic in ionic bonding, can act as pivot joints for constructing tunable 2D MOFs by bonding to dihalogen groups in organic molecules. We take 2,3,6,7,10,11-hexabromotriphenylene, a 3-fold polycyclic molecule with three ortho-dibromo groups, and sodium (Na) atoms as a model system and successfully construct Na-based MOFs on Au(111) surface. The deflection angle of the Na coordination nodes is variable in an unprecedentedly large range between ±36° that allows the construction of multiple 2D MOF architectures. Such a flexible alkali-halogen bonding may provide a unique toolbox for designing and constructing more tunable MOFs by choosing various alkali atoms and halogen moieties.

Metal–organic frameworks (MOFs) have been widely studied due to their versatile applications and easily tunable structures. However, heteroatom‐metal coordination dominates the MOFs community, and the rational synthesis of carbon–metal coordination‐based MOFs remains a significant challenge. Herein, two‐dimensional (2D) MOFs based on silver–carbon linkages are synthesized through the coordination between silver(I) salt and isocyanide‐based monomers at ambient condition. The as‐synthesized 2D MOFs possess well‐defined crystalline structures and a staggered AB stacking mode. Most interestingly, these 2D MOFs, without π–π stacking between layers, exhibit narrow band gaps down to 1.42 eV. As electrochemical catalysts for converting CO2 to CO, such 2D MOFs demonstrate Faradaic efficiency over 92 %. Surprisingly, the CO2 reduction catalyzed by these MOFs indicates favorable adsorption of CO2 and *COOH on the active carbon sites of the isocyanide groups rather than on silver sites. This is attributed to the critical σ donor role of isocyanides and the corresponding ligand‐to‐metal charge–transfer effect. This work not only paves the way toward a new family of MOFs based on metal–isocyanide coordination but also offers a rare platform for understanding the electrocatalysis processes on strongly polarized carbon species.

Dendritic fibrous nano metal organic framework: A magnetic core-shell structure as high performance material for electrochemical capacitors

In addition to their adjustable functionality, structural tunability, and compositional tunability, metal–organic frameworks (MOFs), often known as MOFs, are a distinct form of crystalline porous material. When reduced to two dimensions, ultrathin layers of MOF retain more of its fantastic external features, which is beneficial for a variety of technological applications. Due to their ultrathin atomic-level thickness, easily modifiable structure, and huge surface area, 2D MOF nanosheets and nanocomposites have been the subject of significant research. MOFs are considered intriguing materials for removing toxic contaminants among the novel technologies taken into account in water remediation processes because they exhibit numerous qualities that make them advantageous in water treatment: large surface area, easily functionalizable cavities, a few stable in water, large-scale synthesis, etc Nowadays, water pollution is a rising environmental concern that must be addressed. Due to their special qualities, which include chemical activities, a variety of functionalities, excellent stability, and the ability to be modified for the detection or adsorption of particular molecules, MOFs are widely used in detecting and removing contaminants from water. This review explores most recent wastewater treatment advancements (WWT) using the 2D MOFs mechanism.

Two-dimensional (2D) metal-organic framework (MOF) membranes are considered potential gas separation membranes of the next generation due to their structural diversity and geometrical functionality. However, achieving a rational structure design for a 2D MOF membrane and understanding the impact of MOF nanosheet stacking modes on membrane separation performance remain challenging tasks. Here, we report a novel kind of 2D MOF membrane based on [Cu2 Br(IN)2 ]n (IN=isonicotinato) nanosheets and propose that synergetic stacking modes of nanosheets have a significant influence on gas separation performance. The stacking of the 2D MOF nanosheets is controlled by solvent droplet dynamic behaviors at different temperatures of drop coating. Our 2D MOF nanosheet membranes exhibit high gas separation performances for H2 /CH4 (selectivity >290 with H2 permeance >520 GPU) and H2 /CO2 (selectivity >190 with H2 permeance >590 GPU) surpassing the Robeson upper bounds, paving a potential way for eco-friendly H2 separation.

The most important topics in the world today are environmental and resource issues. The development of green and clean energy is still one of the great challenges of social sustainable development. Two-dimensional(2D) metal-organic frameworks(MOFs) and derivatives have exceptional potential as high-efficiency electrocatalysts for clean energy technologies. This review summarizes various synthesis strategies and applications of 2D MOFs and derivatives in electrocatalysis. Firstly, we will outline the advantages and uniqueness of 2D MOFs and derivatives, as well as their applicable areas. Secondly, the synthetic strategies of 2D MOFs and derivatives are briefly classified. Each category is summarized and we list classic representative fabrication methods, including specific fabrication methods and mechanisms, corresponding structural characteristics, and insights into the advantages and limitations of the synthesis method. Thirdly, we separately classify and summarize the application of 2D MOFs and derivatives in electrocatalysis, including electrocatalytic water splitting, oxygen reduction reaction(ORR), CO2 reduction reaction(CO2RR), and other electrocatalytic applications. Finally, the development prospects and existing challenges to 2D MOFs and derivatives are discussed.

Resistive random access memory (RRAM) has attracted as candidate in the next generation of non-volatile memory device due to its low power consumption, fast write/erase speed, and high CMOS compatibility 1–3. At present, among various materials, metal-organic frameworks (MOFs) are significantly attracting attention as promising materials for data storage applications due to their advantages of highly ordered pores, large surface area, tunable structure, and subsequent controllable function 4–6. However, it is difficult to apply MOF to RRAM, because synthesis time is generally long and additional step is needed to form the MOF into a thin film. Therefore, there is a need for a new method for synthesizing MOF in the form of a thin film simply and fast. In this work, we simply and fast synthesized a 2D MOF nanosheets, Cu(BDC), in the form of thin film using laser process. The dissolved ligand (terephthalic acid) in the N,N-dimethylformamide (DMF) is dropped on the Cu thin film and then irradiate the laser beam on the active spot. Photon energy of laser is absorbed in the Cu metal film, which generate the photothermal effect. This photothermal effect oxides the Cu atom into Cu ion and the oxidized Cu ions are used as metal source of Cu(BDC). This process simply and quickly transforms the Cu thin film into a Cu(BDC) thin film that can act an active layer of RRAM. The suggested method not only is finished in minutes, but also does not needed additional process step of transferring the MOF onto the thin film. The fabricated 2D MOF based-RRAM shows a typical bipolar switching behavior. Our device also exhibits a high on/off ratio (>103), low set/reset voltages (1 V > in SET and -0.5 V > in RESET), and long retention (1×104 s). Therefore, our research suggests a simple and rapid synthesis method of MOFs in the form of a thin film by using laser process and demonstrates applicability 2D MOF fabricated by laser process for the non-volatile memory device. Figure Caption Figure (a) Schematics of synthesis of metal-organic frameworks (MOFs) using laser process. (b) Scanning electron microscopy (SEM) image of Cu(BDC) thin film surface. (c) Transmission electron microscopy (TEM) image of single Cu(BDC) nanosheet. (d) Current-voltage (I-V) curve for 2D MOF based-RRAM device. (e) Retention tests of 2D MOF based-RRAM device. Figure 1

Complexation of copper(II) 2,3,9,10,16,17,23,24-octahydroxy-29H,31H-phthalocyanine (CuPcOH) with copper(II) ions gives a two-dimensional (2D) metal-organic framework (MOF). This is the first report of a phthalocyanine-based MOF. This 2D MOF was obtained as a black powder and showed an electrical conductivity of 1.6×10-6 S cm-1 at 80 °C. When this MOF is used as a cathode of lithium ion battery (LIB), large charge/discharge capacities of 151/128 mAh g-1 were obtained. In addition, it showed a good stability during 200 charge/discharge cycles. The obtained LIB performance mainly originates from the electrically conductive and redox-active framework of the phthalocyanine-based 2D MOF and its hierarchical microporous/mesoporous structure.

Constructing nanomaterials mimicking the coordination environments of natural enzymes may achieve biomimetic catalysis. Here we construct a two-dimensional (2D) metal-organic framework (MOF) nanosheet catalyst as an artificial antioxidase for nanocatalytic rheumatoid arthritis treatment. The 2D MOF periodically assembles numbers of manganese porphyrin molecules, which has a metal coordination geometry analogous to those of two typical antioxidases, human mitochondrial manganese superoxide dismutase (Mn-SOD) and human erythrocyte catalase. The zinc atoms of the 2D MOF regulate the metal-centered redox potential of coordinated manganese porphyrin ligand, endowing the nanosheet with both SOD- and catalase-like activities. Cellular experiments show unique anti-inflammatory and pro-biomineralization performances of the 2D MOF, while in vivo animal model further demonstrates its desirable antiarthritic efficacy. It is expected that such a nanocatalytic antioxidation concept may provide feasible approaches to future anti-inflammatory treatments.

A 3D metal-organic framework with a pcu net constructed from lead(II) and thiophene-2, 5-dicarboxylic acid: Synthesis, structure and ferroelectric property

Two-dimensional (2D) metal organic frameworks (MOFs), are an emerging class of layered nanomaterials with well-defined structure and modular composition. The unique pore structure, high flexibility, tunability, and ability to introduce desired functionality within the structural framework, have led to potential use of MOFs in biomedical applications. This article critically reviews the application of 2D MOFs for therapeutic delivery, tissue engineering, bioimaging, and biosensing. Further, discussion on the challenges and strategies in next generation of 2D MOFs are also included. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Photocatalytic degradation of pollutants is an effective environment purification strategy. Metal-organic frameworks (MOFs) have attracted extensive attention in the field of photocatalysis owing to their structural diversity, uniform cavity, and large specific surface area. However, poor electrical conductivity, light absorption, and water stability restrict their development. The tailorable structure of MOFs may effectively overcome these limitations. Herein, three Cu-based MOFs (complexes 1-3) with one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) structures, respectively, were successfully prepared by introducing different uncoordinated ligands and adjusting the ligand/metal salt ratio. Among them, complex 1 with a 1D chain was constructed as a typical J-type aggregation by π-π stacking interactions between adjacent naphthalene rings. This intermolecular aggregation mode enhances strong exciton coupling between conjugated rings, reduces the transition energy, expands the intrinsic light absorption edge, and provides a channel for electron transport, thus improving the charge-separation efficiency. As expected, complex 1 with a 1D chain structure exhibited excellent Fenton-like catalytic activity. The apparent reaction rates were 3.2 and 2.0 times higher than those of 2D and 3D MOFs, respectively.

A collection of more than 20,000 experimentally derived crystal structures for metal-organic frameworks (MOFs) that do not have two- or three-dimensional covalently bonded networks has been developed from the materials available at the Cambridge Crystallographic Data Centre. Of these 20,000 1D MOFs, more than 12,000 structures have been verified to be solvent-free and in exact agreement with the stoichiometry of the synthesized materials. More than 10% of the complete data set comprise materials including two or more distinct metals. The band gaps of more than 12,000 1D MOFs have been computed at the density functional theory-generalized gradient approximation level, finding more than 2000 materials that have a zero band gap. Molecular simulations of CH4 adsorption in a small number of 1D MOFs indicated that adsorbate-induced deformation plays a significant role in determining adsorption isotherms in these materials. As a result, methods that have been used previously for high-throughput predictions of molecular adsorption in 3D MOFs are not suitable for 1D MOFs.