Ultrathin Metal-organic Framework Nanosheets Research Articles

Designing 1-nm-Thick MOF Nanosheets with Donor-Acceptor Complexes for Photosynthesis of H2O2 Using Water and Dioxygen Only.

Artificial photosynthesis of hydrogen peroxide (H2O2) presents a promising environmentally friendly alternative to the industrial anthraquinone process. This work designed ultrathin metal-organic framework (MOF) nanosheets on which porphyrin ligand as an electron donor (D) and anthraquinone (AQ) as an electron acceptor (A) are integrated as the D-A complexes. The porphyrin component allows the MOF nanosheets to absorb full-spectrum solar light while the acceptor AQ motif promotes central aluminum ion coordination, hindering layer stacking to achieve a thickness of 1.0 nm. The ultrathin D-A design facilitates the separation of electrons from the MOF skeleton to the AQ motif, which induces the direct two-electron oxygen reduction reaction (ORR) mediated by the reversible redox couple of AQ-AQH2 and multielectron water oxidation reaction (WOR) driven by holes remaining on the porphyrin part. In O2-saturated water, the ultrathin MOF nanosheets outperformed the AQ-free bulk and multilayered counterparts by 2.9 and 2.6 times in H2O2 production, respectively, achieving the apparent quantum yield of 4.8% at 420 nm. It also surpasses other benchmark photocatalysts, including the typical MOF photocatalyst, MIL-125-NH2, and organic polymeric photocatalysts. The ultrathin D-A MOF photocatalyst generated H2O2 via both two-electron ORR as a major path and two-electron WOR as a minor path. This approach presents a promising strategy for the rational design of efficient nanostructured photocatalysts for solar fuels and chemicals.

Enhancing the charge storage capacity of ultrathin metal–organic framework nanosheets with CO2-derived carbon nanotubes

Metal-organic frameworks (MOFs) hold promise as efficient electrode materials for supercapacitors, but their practical application is hindered by the intrinsic low electrical conductivity. Here, we employ CO2-derived carbon nanotubes based on molten salt electrolysis (MSE-CNTs) as the framework to guide the growth of nickel-based MOF (Ni-MOF). The resulting MSE-CNTs/Ni-MOF composite exhibits an impressive specific capacitance of 1714.2 F g−1 at 1 A g−1, 1.45 and 1.26 times greater than bare Ni-MOF (1185.7 F g−1) and CVD-CNTs/Ni-MOF (1364.3 F g−1, the composite of Ni-MOF and commercial CNTs produced by chemical-vapor-deposition), respectively. Moreover, the assembled hybrid supercapacitor (MSE-CNTs/Ni-MOF//active carbon) achieves a remarkable specific capacitance of 136.5 F g−1 at 1 A g−1 and an energy density of 54.8 Wh kg−1 at 850 W kg−1, standing among the best of the state-of-the-art. The superior capacitive performance of MSE-CNTs/Ni-MOF than CVD-CNTs/Ni-MOF can be attributed to the better electrical conductivity of MSE-CNTs, the thinner nanosheet architecture of MSE-CNTs/Ni-MOF, and the effective electrically conductive network within the composite. This work marks a paradigm shift from greenhouse gas CO2 to excellent energy storage materials, paving the way for addressing both the energy and climate issues simultaneously.

Ultrathin metal-organic framework nanosheets (Cu-TCPP) assembled micro flower combined with endonuclease signal amplification for ultrasensitive detection

Metal-organic framework play an important role in developing novel detection techniques. Herein, an ultrathin two-dimensional (2D) metal-organic framework nanosheet (Cu-TCPP) assembled microflower was successfully synthesized and applied for ultrasensitive detection. The high detection performance of Cu-TCPP microflower was attributed to high-capacity aptamer adsorption and specific desorption resulting from numerous approachable active sites, and its ultrathin nanosheets microflower-like structure. Moreover, the Cu-TCPP microflower had overcame the disadvantages of 2D MOF nanosheets which tended to agglomerate. Moreover, it exhibited excellent fluorescence quenching performance as a donor for fluorescence resonance energy transfer. Acetamiprid, a new chloronicotinic neurotoxic insecticide was used as the model analyte. The ultrasensitive sensor was developed by combining the Cu-TCPP microflower with deoxyribonuclease Ⅰ signal enhanced fluorescence. When acetamiprid was present, the fluorescent labeled aptamer probe was selectively bound to acetamiprid and desorbed from the Cu-TCPP microflower, resulting in fluorescence recovery. Subsequently, DNase Ⅰ was used to cleave the DNA strands of the aptamer probe, and acetamiprid was released to participate in a new cycle. The detection limit of the assay was as low as 5.56 pg/mL with a linear range 50.00 pg/mL∼5.00 μg/mL, and it was a universal platform to detect other analytes.

Ultrathin MOF nanosheets and their mixed-matrix membranes for ammonia and aliphatic amine sensing in water.

Ultrathin 2D metal-organic frameworks (MOFs) exhibit a myriad of unparalleled properties, rendering them extensively applicable across various fields. Despite this, developing a 2D MOF sensor for detecting hazardous amines in water remains a formidable challenge. To address this issue, we synthesized Ni-btc MOF ultrathin nanosheets with a thickness of approximately 4.15 nm for the detection of amines in water. These nanosheets demonstrated a notable "turn-on" fluorescence response in the presence of ammonia and aliphatic amines. The detection limit for aliphatic amines ranged from 297 to 424 nM, while for ammonia, it reached an impressive low limit of around 42 nM, which is an excellent value compared to other reported MOFs for ammonia sensing in water. Density functional theory calculations elucidated the mechanism underlying fluorescence enhancement. Additionally, a mixed matrix membrane based on MOF nanosheets was fabricated for real-time sensing that exhibits an immediate color change in the presence of ammonia and aliphatic amines.

Fabrication of Carboxylate-Functionalized 2D MOF Nanosheet with Caged Cavity for Efficient and Selective Extraction of Uranium from Aqueous Solution.

The efficient removal of radioactive uranium from aqueous solution is of great significance for the safe and sustainable development of nuclear power. An ultrathin 2D metal-organic framework (MOF) nanosheet with cavity structures was elaborately fabricated based on a calix[4]arene ligand. Incorporating the permanent cavity structures on MOF nanosheet can fully utilize its structural characteristics of largely exposed surface area and accessible adsorption sites in pollutant removal, achieving ultrafast adsorption kinetics, and the functionalized cavity structure would endow the MOF nanosheets with the ability to achieve preconcentration and extraction of uranium from aqueous solution, affording ultrahigh removal efficiency even in ultra-low concentrations. Thus, more than 97% uranium can be removed from the concentration range of 50-500µgL-1 within 5min. Moreover, the 2D nano-material exhibits ultra-high anti-interference ability, which can efficiently remove uranium from groundwater and seawater. The adsorption mechanism was investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) analysis, and density functional theory (DFT) calculations, which revealed that the cavity structure plays an important role in uranium capture. This study not only realizes highly efficient uranium removal from aqueous solution but also opens the door to achieving ultrathin MOF nanosheets with cavity structures, which will greatly expand the applications of MOF nanosheets.

Ultrathin Metal-Organic Framework Nanosheets for Selective Photocatalytic C2 H2 Semihydrogenation in Aqueous Solution.

The selective semihydrogenation of C2 H2 to C2 H4 in crude C2 H4 (with ~1 vol % C2 H2 contamination) is a crucial process in the manufacture of polyethylene. Comparing to conventional thermalcatalytic route with Pd as catalyst under high temperature with H2 as hydrogen source, photocatalytic C2 H2 reduction reaction with H2 O as hydrogen source can achieve high selectivity under milder conditions, but has rarely been reported. Here, we present a kind of ultrathin metal-organic framework nanosheets (Cu-Co-MNSs) that demonstrate excellent catalytic activities in the semihydrogenation of C2 H2 . Employing Ru(bpy)3 2+ as the photosensitizer, this catalyst attains a noteworthy turnover number (TON) of 2124 for C2 H4 , coupled with an impressive selectivity of 99.5 % after 12 h visible light irradiation. This performance is comparable to molecular catalysts and notably surpasses the efficiency of bulk metal-organic framework materials. Furthermore, Cu-Co-MNSs achieve a 99.95 % conversion of C2 H2 under industrial relevant conditions (1.10 % C2 H2 in C2 H4 ) with 90.3 % selectivity for C2 H4 over C2 H6 , demonstrating a great potential for polymer-grade C2 H4 production.

Scalable and sustainable manufacturing of ultrathin metal–organic framework nanosheets (MONs) for solar cell applications

Metal-organic framework nanosheets (MONs) are an emerging class of 2D materials whose tunable chemistry make them ideal for a wide range of sensing, catalytic, electronics and separation applications. However, creating scalable routes to the synthesis of high quality, ultrathin nanosheets remains challenging and little consideration has been given to the economics of making these materials. Here, we demonstrate a scalable synthesis of zinc-porphyrin based nanosheets, Zn2(H2TCPP), for use in organic solar cells and conduct a techno-economic analysis of their pilot-plant scale manufacture. A thorough investigation of the process chemistry of the solvothermal synthesis enabled reduction of reaction time, increased solid content and scale-up of the reaction in batch. Significantly, the addition of triethylamine accelerated the reaction kinetics, which enabled the synthesis temperature to be dropped from > 80 °C to room temperature. Application of these new reaction conditions in a continuous stirred-tank reactor directly formed monolayer MONs at 99 % yield with a space–time yield of 16 kg m−3 day−1, an approximately 20-fold increase in yield compared to adapting the literature procedure. Techno-economic analysis showed a 94 % reduction in the production costs compared to the literature reaction conditions and indicated that the production cost was dominated by ligand price. The general applicability of the method was demonstrated through synthesis of related Cu2(H2TCPP) MONs and tunability through metalation of the porphyrin units with six different metal ions. Finally, the value of the nanosheets was demonstrated through a near doubling in the power conversion efficiency of organic photovoltaic devices when the MONs were incorporated into the active layer. Overall, this work demonstrates the first scalable and sustainable route to producing monolayer nanosheets for high value applications.

Ultrathin metal-organic framework nanosheets (Cu-TCPP)-based isothermal nucleic acid amplification for food allergen detection

The rapid and accurate detection of peanuts and soybeans allergen is important to the food safety. In this study, Cu-TCPP nanosheet, a kind of ultra-thin metal-organic framework (MOF) was synthesized and applied in loop-mediated isothermal amplification (named Cu-TCPP@LAMP), which can inhibit the non-specific amplification by absorbing and precise temperature releasing of single primer. As thus, Cu-TCPP@LAMP can achieve high sensitivity and specific amplification of the target gene. As a result, peanut and soybean allergens genes contained in food were successfully detected with a favorable detection sensitivity (5 ng/μL for peanuts and 10 ng/μL for soybeans) and reliable repeatability (The coefficient of variation was 3.38% for peanuts and 3.33% for soybeans). Moreover, the established method was utilized for detection of several commercial products, and had a high consistency with the standard method. Apart from food allergens, this novel assay can be widely used in other areas, such as pathogen detection, tumor nucleic acid detection and so on.

Sustainable metal-organic framework co-engineered glass fiber separators for safer and longer cycle life of Li-S batteries

Most of the issues with making Li–S batteries are caused by the growth of Li dendrites and the movement of polysulfide. To solve both of these problems at the same time, this study describes the placement of Cu or Fe atoms on an ultrathin metal organic framework (MOF) nanosheet-based glass fiber separator for making Li–S batteries that are safe and last a long time. Cu or Fe atoms coordinated with oxygen atoms on the surface of ultrathin MOF nanosheets can greatly facilitate the movement of Li ions while acting as "traps" to stop polysulfide from moving around by introducing the Lewis acid-base interaction. Because of this, the Li–S cells with the Cu/MOF or Fe/MOF coatings on the glass fiber separator show long-term cycling stabilities with low-capacity decay of 0.080% and 0.057% per cycle over 400 cycles, respectively. Furthermore, Li–S cells assembled with the Cu/MOF and Fe/MOF separators show capacity retention of 985 and 1237 mAh g−1, respectively, after 400 cycles, indicating the potential of the Cu/MOF and Fe/MOF separators for practical applications.

Surface-Modified Ultrathin Metal–Organic Framework Nanosheets as a Single-Site Iron Electrocatalyst for Oxygen Evolution Reaction

Surface-Modified Ultrathin Metal–Organic Framework Nanosheets as a Single-Site Iron Electrocatalyst for Oxygen Evolution Reaction

Ultrathin metal organic framework nanosheets with rich defects for enhanced fluoride removal

Herein, we present a defluoridation approach based on ultrathin two-dimensional metal organic framework (MOF, viz., Ce-DCPBA) nanosheets. The nanosized layers and ultimately exposed metal defects of Ce-DCPBA enable the high-capacity adsorption of fluoride in a wide pH window. Attributed to tailored ligand exchange at metal defects and boron-fluoride complexation, Ce-DCPBA exhibits exceptional selectivity for fluoride with a partition coefficient up to 18.805 L g−1, even in the matrixes with ultrahigh salinity (8 mol/L of nitrate). Negligible interference from other anions, superior adsorption ability and favorable reusability promotes the practical application of Ce-DCPBA for the selective and efficient removal of fluoride from complex environmental samples. These findings furnish a promising strategy for the anesis of fluoride contamination, and illuminate the application potentials and superiorities of ultrathin MOFs-based nanostructures for environmental remediation.

Ultrathin Metal-Organic Framework Nanosheets Exhibiting Exceptional Catalytic Activity.

Two-dimensional (2D) metal-organic framework nanosheets (MONs) or membranes are classes of periodic, crystalline polymeric materials that may show unprecedented physicochemical properties due to their modular structures, high surface areas, and high aspect ratios. Yet preparing 2D MONs from multiple components and two different types of polymerization reaction remains challenging and less explored. Here, we report the synthesis of MOF films via interfacial polymerization, which involves three active monomers for simultaneous polycondensation and polycoordination taking place in a confined interface. The well-defined lamellar structure of the MOF films allowed feasible and scalable exfoliation to produce free-standing 2D MONs with high aspect ratio up to 2000:1 and ultrathin thickness (∼1.7 nm). The pore structure was revealed by high-resolution TEM images with near-atomic precision. The imide-linkage of MONs provided superior thermal (up to 530 °C) and good chemical stability in the pH range from 3 to 12. More importantly, the MONs exhibited exceptional catalytic activity and superior reusability for the hydroboration reactions of alkynes, in which the turnover frequency (TOF) reached 41734 h-1, which is 2-4 orders of magnitude greater than that reported for homogeneous and heterogeneous catalysts.

Rational construction of 2D/2D Ti3C2Tx/NiCo MOF heterostructure for highly efficient Li+ storage

Metal-organic framework (MOFs) have been regarded as ideal lithium-ion battery (LIB) anodes with abundant active sites, porous structure, shortened ion diffusion pathways, and adjustable component, but the MOF anodes suffer from the low electronic conductivity. Herein, we rationally design a 2D/2D Ti3C2Tx/NiCo MOF heterostructure through in-situ growth of ultrathin NiCo MOF nanosheets on the few-layer Ti3C2Tx MXene sheets. The carboxylate groups of BDC2− can form stable bond with the termination groups (e.g., -OH) on the Ti3C2Tx surface and hydroxyl groups in the lignin molecules, resulting in stable Ti3C2Tx/NiCo MOF interface and good structure stability of the 2D/2D Ti3C2Tx/NiCo MOF heterostructure. The Ti3C2Tx/NiCo MOF heterostructure could combine the advantages of 2D MXene nanosheets and 2D bimetallic MOF structure. The 2D bimetallic NiCo MOF can offer plenty of exposed active sites for Li+ intercalation, while the 3D conductive network structure based on the Ti3C2Tx can not only enhance the electronic conductivity, but also facilitate the electrode/electrolyte interface contact and promote the charge diffusion. The obtained 2D/2D Ti3C2Tx/NiCo MOF heterostructure anode demonstrates a high capacity of 637 mAh g−1 at 0.2 A g−1 after 200 cycles. Furthermore, the Li+ intercalation/extraction mechanism of the Ti3C2Tx/NiCo MOF heterostructure electrode is explored in detail.

Edge engineering of platinum nanoparticles via porphyrin-based ultrathin 2D metal–organic frameworks for enhanced photocatalytic hydrogen generation

Edge-doping engineering in metal nanoparticles (MNPs) is always hard to achieve due to the high surface energy of the hybrid MNPs, while porphyrin-based ultrathin two-dimensional (2D) metal–organic framework (MOF) is demonstrated the positive role in stabilize this structure. Herein, a bottom-up method was developed to prepare platinum nanoparticles (PtNPs)-decorated 2D MOF nanosheets, where a porphyrin ligand of Pd-metalized tetrakis(4-carboxyphenyl)porphyrin (PdTCPP) was applied to synthesize ultrathin MOF nanosheets as Zr-TCPP(Pd) in high yield. Attributing to the high superficial area of ultrathin Zr-TCPP(Pd) nanosheets, Pt NPs can well anchor uniformly with small nanoparticle size to obtain 2% Pt/Zr-TCPP(Pd) hybrid nanosheets, which showed a higher photocatalytic hydrogen production rate of 3348 μmol g-1h−1. This is attributed to the coordination between Zr4+ and C = O of PVP, which promotes the contact between PtNPs and Zr-TCPP(Pd) nanosheets. As a result, the long-life electrons of PdTCPP photosensitizers are rapidly transferred to the electron capture center PtNPs, and the photoelectron-hole recombination is effectively inhibited. The apparent quantum efficiency of 2% Pt/Zr-TCPP(Pd) reaches up to 1.56% at 420 nm. The density functional theory (DFT) calculations revealed the Pd-doped position in Pt79 nanoparticle is important that the Pt78Pdsurf. model (Pd atom was doped on the surface of Pt nanoparticle) showed the highest activity with abundant exposed active region.

Development of High Throughput Photopolymerizations Using Micron-Sized Ultrathin Metal-Organic Framework Nanosheets.

Polymer syntheses in a high throughput format are still challenging due to the tedious procedures for prior deoxygenation and catalyst removal. 2D metal-organic framework (MOF) nanosheets are advantageous for elevating the catalytic efficiency and catalyst recyclability. Polymerization of a wide variety of monomers, including hydrophilic acrylamides and hydrophobic acrylates, is attempted directly in a multi-well plate by employing Zn-ZnPPF-2D nanosheets (PPF=porphyrin paddlewheel framework) as a heterogeneous photocatalyst. Various parameters such as monomer concentration, catalyst concentration, and light wavelength are investigated with respect to their effects on polymerization rate and the degree of control over the molecular weight and molecular weight distribution. Due to the larger surface area and more accessible catalytic sites, the top-performing Zn-ZnPPF-2D exhibits fast polymerization kinetics over the Zn-ZnPPF-3D bulk crystals. In addition, the synthesis of triblock copolymers with a single loading of catalysts confirms the outstanding catalytic performance of these 2D MOF catalysts. Finally, photopolymerization is demonstrated to be achievable entirely in a microliter-scale human cell culture medium. As such, this strategy provides high levels of control and precision over macromolecular synthesis outcomes that best align with the requirements of high throughput approaches toward biological applications.

Controllable In Situ Transformation of Layered Double Hydroxides into Ultrathin Metal-Organic Framework Nanosheet Arrays for Energy Storage.

Ultrathin two-dimensional metal-organic frameworks (MOFs) have convincing performances in energy storage, which can be put down to their accessible active sites with rapid charge transfer. Herein, NiCo-layered double hydroxide (LDH) nanosheet arrays are used as self-sacrificial templates to in situ fabricate ultrathin NiCo-MOF nanosheet arrays on Ni foam (NS/NF) by using organic ligands without adding metal sources. Two ultrathin MOF nanosheets with different ligands, terephthalate (BDC) and 2-aminoterephthalate (NH2-BDC), are synthesized, characterized, and discussed in detail. Specifically, NiCo-NH2-BDC-MOF NS/NF exhibits the best electrochemical performance as a battery-type electrode for supercapacitors, achieves an areal capacitance of 12.13 F cm-2 at a current density of 2 mA cm-2, and retains the original capacitance of 73.08 % after 5000 cycles at a current density of 50 mA cm-2. Furthermore, when NiCo-NH2-BDC-MOF NS/NF is assembled with activated carbon (AC) to form an asymmetric supercapacitor (ASC), an energy density of 0.81 mWh cm-2 can be provided at a power density of 1.60 mW cm-2. These results offer an effective and controllable synthetic strategy to in situ prepare ultrathin MOF nanosheet arrays with different ligands and metal ions from LDH precursors.

Ultrathin metal-organic framework nanosheets as building blocks of lamellar nanofilms for ultrafast molecular sieving.

Metal-organic framework (MOF) nanosheets have significant potential applications including separation, catalysis, and sensors. However, the on-demand design with tunable thickness and morphology remains a great challenge, leading to difficulties in modulating their hierarchical assembly for the preparation of macroscopic films. Herein, we report the successful synthesis of smooth and ultrathin MOF (Cu-TCPP (TCPP = 4,4,4,4-(porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid))) nanosheets used in lamellar nanofilms for the rejection of organic molecules from water. Dopamine hydrochloride (DA-HCl) is used as an adjuvant in the synthesis. Facilitated by a HCl acid environment and DA competitive coordination, the normal and lateral growths of Cu-TCPP nanosheets are modulated to achieve the desired thickness and morphology. DA-HCl can be also easily removed from the nanosheets without affecting their physicochemical properties. The as-synthesized nanosheets are utilized as nanofilm building blocks in which they are stacked into ordered bricks. The obtained membrane displays an ultrahigh water permeance of 2540 L m-2 h-1 bar-1, which is two orders of magnitude higher than the currently reported polymer membranes, while it does not sacrifice the solute rejection as completely determined by the intrinsic pore size of the nanosheets (i.e., 98.8% for molecules larger than 1.3 nm). This work provides a novel and facile strategy to tailor the morphology of the MOF nanosheets for maximizing their functionalities and structure superiority in many engineering applications.

2D Co-UMOFNs filled PEBA composite membranes for pervaporation of phenol solution

Two-dimensional Co ultrathin metal–organic framework nanosheets (Co-UMOFNs) were synthesized and blended into poly (ether block amide) (PEBA) to prepare composite mixed matrix membranes on PVDF supports for the pervaporation of phenol aqueous solution. The membranes were characterized by XRD, ATR-IR, TGA, CA and SEM measurements. Effects of the Co-UMOFNs loading, feed temperature and feed concentration on phenol separation performance were investigated. The results showed that Co-UMOFNs have a two-dimensional layered morphology and have good compatibility with the PEBA. A “brick and mortar” architecture morphology was achieved after incorporating Co-UMOFNs into the PEBA membrane. The amorphous PE segments in the PEBA were turned into a crystalline structure, restricting the motion of PE segments. The filling of Co-UMOFNs slightly improved the thermal stability and hydrophobicity as well. With the increase of the Co-UMOFNs loading from 0% to 40%, the phenol separation factor increased from 27 to 45, and the total flux decreased from 1.2 kg m-2h-1 to 0.42 kg m-2h-1, when separation of 1000 ppm phenol solution at 70 °C. The interlayer galleries induced by the Co-UMOFNs stacking increased the tortuosity, and the crystalline structure of the Co-UMOFNs-PEBA improved the energy barriers of water penetration. Therefore the water flux was inhibited and the phenol separation factor increased. Depression of water permeation can be another protocol to prepare high-performance organophilic pervaporation membranes.

Unsaturated NiII Centers Mediated the Coordination Activation of Benzylamine for Enhancing Photocatalytic Activity over Ultrathin Ni MOF-74 Nanosheets.

Creating accessible unsaturated active sites in metal-organic frameworks (MOFs) holds great promise for developing highly efficient catalysts. Herein, ultrathin Ni MOF-74 nanosheets (NMNs) with high-density coordinatively unsaturated NiII centers are prepared as a photocatalyst. The results of in situ ATR-IR, Raman, UV-vis DRS, and XPS suggest that abundant NiII centers can act as the active sites for boosting benzylamine (BA) activation via forming -Ni-NH2- coordination intermediates. The generation of coordination intermediates assists the transfer of photo-generated holes to BA molecules for producing BA cation free radicals, better impelling the breaking of N-H bonds and the photooxidation of BA molecules. The photo-generated electrons further activate O2 molecules to O2•- radicals for triggering the reaction. The experiments reveal that the coordination activation of BA molecules may be a rate-determining step on NMNs rather than the adsorption and activation of O2 molecules. Moreover, NMNs possess a better ability for the separation of photo-generated carriers in comparison with bulk Ni MOF-74 (NMBs). As a result, NMNs achieve a kinetic rate constant of 0.538 h-1 for the photocatalytic oxidative coupling of BA under visible light, about 50 times higher than that of NMBs (0.0011 h-1). Finally, a probable synergetic catalytic mechanism with coordination activation and photocatalysis is discussed on a molecular level. This study not only highlights the importance of coordination activation for heterogeneous photocatalysis but also affords an inspiration for building ultrathin MOF nanosheets.

Ultrathin Metal–Organic Framework Nanosheets as Nano‐Floating‐Gate for High Performance Transistor Memory Device

AbstractMetal–organic framework (MOF) is an emerging important class of functional materials in the fields of information storage, wearable electronics and optoelectronic devices. The interaction of electrons or holes with MOFs is important for the systematic exploration of MOFtronics and to investigate the related structure–performance correlation. Herein, MOF flat nanosheets of copper tetrakis(4‐carboxyphenyl)porphyrin with sub‐10 nanometer scale in thickness are employed as the charge‐trapping layer in organic field‐effect floating‐gate transistor memory device fabricated by an air–liquid interfacial assembly and subsequent stamping operation. As charge trapping sites, MOF nanosheets with ultrathin nanoporous arrays significantly improve in comparison with the memory device using its counterpart ligand of tetrakis(4‐carboxyphenyl)porphyrin as the trapping elements. As compared to the reported widely applied nanofloating gate materials of gold nanoparticles, graphene, or macromolecular nanomaterials, a short pulse (≈20 ms) on the device gets a considerable memory window of ≈37.5 V at a programming voltage of ‐80 V, with a retention time longer than 104 s and good ON/OFF ratio of >103. Furthermore, the hybrid structure composed of metal and organic components endows it with electron and hole trapping capability. This work could push forward the fundamental research of organic–inorganic–hybrid electronics in future microelectronic research.