Ultrathin MOF Research Articles

Ultrathin Ni-Fe MOF Nanosheets: Efficient and Durable Water Oxidation at High Current Densities.

Efficient, durable, and economical electrocatalysts are crucial for advancing energy technology by facilitating the oxygen evolution reaction (OER). Here, ultrathin Ni-Fe metal-organic skeleton (MOF) nanosheets were created in situ on nickel foam (NiFe-UMNs/NF). The catalyst exhibited excellent OER catalytical abilities, with only 269 mV overpotentials at 250 mA cm-2. Besides, when integrated with Pt/C/NF, NiFe-UMNs/NF held the potential for application in industrial alkaline water electrolysis with an initial voltage retention of approximately 86% following a continuous operation of 100 h at a current density of 250 mA cm-2. The super performance of the NiFe-UMNs/NF catalyst was attributed to ultrathin morphology, super hydrophilicity, and synergistic effects between Ni and Fe within the MOF. In situ Raman showed that NiFe-UMNs were converted to NiFeOOH as the active species in the OER process. Density functional theory revealed that iron doping accelerated the rate-determining step and reduced the OER reaction energy barrier. This work elucidated a promising electrocatalyst for OER and enriched the practical implementation of MOF materials.

Ultra-thin size-sieving gas separation membrane by precisely contra-diffusion-match growth of ZIF-67 among GO laminates

Ultrathin and defect-free MOF membranes are actively pursued to realize high-performance hydrogen purification and carbon capture, which are of great significance for energy conservation and environmental sustainability. Zeolitic imidazolate framework-67 (ZIF-67) possesses exceptional pore apertures for sieving hydrogen from other larger gases. However, the preferential heterogeneous nucleation and growth of ZIF-67 crystals greatly challenge the synthesis of ZIF-67 membranes. In this work, a tunable-reaction-zone contra-diffusion synthesis is proposed to effectively assemble ZIF-67 nanocrystals into ultrathin GO laminates. The contra-diffusion-match growth of ZIF-67 constructs a compact ZIF-67@GO hybrid structure with superior H2/CO2 separation factor of 140.8 and H2 permeance of 1.7 × 10−7 mol m−2 s−1 Pa−1, transcending the state-of-art upper bounds. The excellent separation performance is attributed to the collaborative effect of the size-sieving and the selective attraction of the ZIF-67@GO hybrid structure. Long-term operation also reveals the superior stability of the ZIF-67@GO hybrid membrane for H2/CO2 separation. The rational-design approach grants a novel way to fabricate ultrathin and defect-free ZIF-67 crystalline membranes for high-performance gas separation.

The electrocatalytic self-reconstruction of ultrathin 2D MOF nanoarrays supported on alloy foam improves the oxygen evolution reaction

Investigating the self-reconstruction process of MOF-supported electrodes is of significant importance for understanding the reaction mechanisms in electrocatalytic oxygen evolution reaction (OER). By using 1,1′-ferrocenedicarboxylic acid (FcDA) as the ligand and NiFe foam (NFF) as the current collector, a self-supported T50NiFc-MOF/NFF electrode was synthesized through the introduction of triethylamine (TEA) to regulate the deprotonation process. The optimized T50NiFc-MOF/NFF exhibited excellent electrocatalytic OER performance, requiring only 217 mV to drive a current density of 10 mA cm−2, surpassing commercial RuO2. Additionally, the T50NiFc-MOF/NFF showed a remarkable electrocatalytic stability of over 70 h. The unique 2D MOF nanoarrays and strong coordination bonds between the metal and ligand in the as-prepared self-supported electrode contribute to the enrichment of electrochemical active sites and catalytic stability. Through a self-construction process, the 2D MOF nanoarrays on the electrode surface were in-situ converted into a more active metal-LDH during alkaline electrocatalysis, which played a crucial role in improving the electronic structure of the electrode, demonstrating its importance in achieving efficient OER processes.

Two-dimensional layered MOF nanosheets with multiple binding sites for selective detection and removal of Fe(III) ions

Heavy metal contamination has become an urgent global concern, posing a significant threat to our environment and health. Hence, it is critical to exploit functional materials for heavy metal ions sensing and elimination. However, the development of multifunctional materials that can simultaneously accomplish the selective detection and removal of the metal ions remains a significant challenge. In this work, a two-dimensional (2D) layered metal–organic framework (LMOF) functionalized with diverse binding sites has been utilized to concurrently detect and remove Fe3+ ions. The LMOF [Zn(hsb-2) (5-aipa)](HSB-W15) was rationally designed and constructed from the mixed ligands of hsb-2 (1,2-bis(4′-pyridylmethylamino)-ethane) and 5-aipa (5-aminoisophthate) under mild condition. In addition, the corresponding ultrathin nanosheets HSB-W15-NS were also obtained by adapting the instant in situ exfoliation (IISEM) method. Owing to the ultrathin nanosheet morphology and an abundance of active sites on the surface, HSB-W15-NS nanosheets can function as an effective fluorescent sensor to detect Fe3+ and Cr3+ ions. Exceptionally, HSB-W15-NS can also be used to selectively capture Fe3+ ions from water, with up to 93 % removal efficiency, and the adsorption equilibrium attained in 5 min. The sensing and adsorption processes were investigated based on kinetic model analysis, Fourier transform infrared spectroscopy, Raman spectrum analysis, density functional theory calculations, and control experiments. This work inspired the development of ultrathin 2D MOF nanosheets for applications in environmental protection.

Scalable 2D/2D Assembly of Ultrathin MOF/MXene Sheets for Stretchable and Bendable Energy Storage Devices

AbstractScalable assembly of two dimensional (2D) lamellar nanomaterials for deformable films has potential in wearable energy storage devices, but overcoming the trade‐off in mechanical and energy storage properties is a challenge. Here, a blade‐coating strategy is reported to develop highly stretchable and bendable metal‐organic frameworks/large‐sized Ti3C2Tx MXene (MOF/LMX) composite films on the pre‐stretched elastomer substrates. The LMX sheets serve as conductive scaffolds for loading the small‐sized ultrathin MOF sheets (SUMOFs), resulting in an improved tensile strength (≈97 MPa) of the films, which guarantees their structural integrity when forming a wavy structure on a relaxed substrate. In addition, SUMOFs incorporated in‐between LMX layers not only expose active redox sites by mitigating the intrinsic self‐restacking of MOF but also accelerate the electron transfer in the redox reaction process revealed through the density functional theory calculations. As a result, the composite films deliver high electrical conductivity (3244 S cm−1) and energy storage capability (1238 F g−1). When assembled into an asymmetric supercapacitor device, it also exhibits stable performances under different bending and stretching states. Thus, the development of conducting and deformable MOF‐based films with high mechanical, electrical, and energy storage properties enables their potential commercial applications for wearable electronics.

Oriented Ultrathin π-complexation MOF Membrane for Ethylene/Ethane and Flue Gas Separations.

Rational design and engineering of high-performance molecular sieve membranes towards C2 H4 /C2 H6 and flue gas separations remain a grand challenge to date. In this study, through combining pore micro-environment engineering with meso-structure manipulation, highly c-oriented sub-100 nm-thick Cu@NH2 -MIL-125 membrane was successfully prepared. Coordinatively unsaturated Cu ions immobilized in the NH2 -MIL-125 framework enabled high-affinity π-complexation interactions with C2 H4 , resulting in an C2 H4 /C2 H6 selectivity approaching 13.6, which was 9.4 times higher than that of pristine NH2 -MIL-125 membrane; moreover, benefiting from π-complexation interactions between CO2 and Cu(I) sites, our membrane displayed superior CO2 /N2 selectivity of 43.2 with CO2 permeance of 696 GPU, which far surpassed the benchmark of other pure MOF membranes. The above multi-scale structure optimization strategy is anticipated to present opportunities for significantly enhancing the separation performance of diverse molecular sieve membranes.

Fabrication of ultrathin 2D MOF nanosheets for folic acid detection

Fabrication of ultrathin 2D MOF nanosheets for folic acid detection

Curtailing the Excess eg-Orbital Filling of a Ni Atom by Enhanced Interatomic Charge Transfer within a Bimetallic 2D Metal–Organic Framework for the Oxygen Evolution Reaction

Electrochemical conversion technologies rely on the design and creation of highly efficient electrocatalysts. The oxygen evolution reaction (OER), which has applications in water splitting and metal–air batteries, is a crucial process in such conversions. Herein, a bimetallic Co, Ni-based ultrathin metal–organic framework nanoribbon (NiCo-NR) is reported for an efficient OER. It is proposed that in ultrathin MOF nanoribbons, the surface atoms (Co, Ni) are coordinatively unsaturated, due to which the interatomic electron transfer within the MOF makes more active adsorption sites on the surface. The catalyst exhibits an overpotential of 244 mV at a current density of 10 mA cm–2 with a Tafel slope value of 85 mV dec–1. For the stability experiment, the catalyst was exposed for 35 h of uninterrupted operation at a current density of 100 mA cm–2. Our findings showed that coordinatively unsaturated transition metal atoms were dominant active sites and the electrocatalytic activity can be tuned by the coupling interactions of Ni and Co metals. The excess eg-orbital filling of the Ni atom, which limits the electrocatalytic performance, can be reduced by π-donation from Ni to Co through the oxygen atom.

Ultra-thin 2D bimetallic MOF nanosheets for highly sensitive and stable detection of glucose in sweat for dancer

The measurement of glucose concentration in sweat is expected to replace the existing blood glucose detection, which realize the effective way of non-invasive monitoring of human glucose concentration in dancing. High precision glucose detection can be achieved by adjusting the electrode material of the sensor. Thus, in this work, the bimetallic organic frameworks (bi-MOFs) materials containing Mn and Ni ions (NiMn-MOF) with ultrathin nanosheets have been exquisitely designed. The ultrathin nanosheet and heterogeneous metal ions in the structure optimize the electronic structure, which improves the electrical conductivity of MOFs. The success of the preparation strategy leads the good electrocatalytic performance of NiMn-MOF for glucose detection. Detailedly, NiMn-MOF shows high sensitivity of 1576 μA mM−1 cm−2 in the linear range from 0 to 0.205 mM and the wide linear region of 0.255–2.655 mM and 3.655–5.655 mM were also observed. In addition, the high repeatability, reproductivity, long-term stability and ultra-low limited of detection (LOD, 0.28 μM, S/N = 3) provide foundation for the practical sensor application of this NiMn-MOF nanosheets. Remarkably, as designed NiMn-MOF sensor can accurately measure glucose in sweat showing great potential in the field of wearable glucose monitoring during dancing.

High-loading single cobalt atoms on ultrathin MOF nanosheets for efficient photocatalytic CO2 reduction

High-loading single cobalt atoms on ultrathin MOF nanosheets for efficient photocatalytic CO2 reduction

Highly efficient and tunable catalytic addition of CO2 with epoxides over 2D Co-TCPP nanosheet at ambient condition

A series of ultrathin (∼1.11–4.80 nm) 2D porphyrinic MOF nanosheets are developed and novel synergistic systems are conveniently constructed for the facile formation of cyclic carbonates. Using n-Bu4NBr (TBAB) as a co-catalyst, ultrathin (ca. 2.58 nm) Co-TCPP exhibited high catalytic activity for the solvent-free conversion of styrene oxide to cyclic carbonate, affording 99% yield at ambient conditions (25 °C and 1 atm CO2). A relatively low energy (19.6 kcal/mol) for the rate-determining step is required for Co-TCPP/TBAB nanosystem as calculated by DFT. Notably, utilizing amino acid ionic liquid (AAIL, [Bmim][Glu] or [Bmim][His]) as the modifier, a substrate-dependent protocol was proposed to fix CO2 with terminal epoxides or cyclohexene oxide, giving cyclic carbonates in 84–99% yields under mild conditions (solvent-free, 80 °C and 1 atm CO2). 13C NMR and UV-vis studies provided insights into the vital roles of AAIL during CO2 capture via carbamate dianion and in situ fabrication of Co-TCPP-AAIL. Moreover, DFT calculations also confirmed the AAIL-regulated substrate-dependent transformation strategy.

Fabrication of ultrathin two-dimensional MOF nanosheets with cage-like cavities showing excellent adsorption for lead(ii)

An ultrathin 2D MOF nanosheet with cage-like cavities was constructed, which showed an outstanding Pb2+ uptake capacity of 738.65 mg g−1 as well as ultrahigh selectivity and anti-interference performance.

Heterogenized molecular Pd(ii) catalyst on ultrathin 2D metal–organic frameworks with nanoflower-like morphology for isonitrile-involved cyclization reaction

An ultrathin 2D MOF based catalyst with fully exposed single-site Pd(ii) active centers shows superior catalytic efficiency for the isonitrile-involved cyclization reaction compared to 3D MOF based Pd(ii) catalyst and homogeneous counterpart.

Implanting of Single Zinc Sites into 2D Metal–Organic Framework Nanozymes for Boosted Antibiofilm Therapy

AbstractDesign of nanozymes with catalytic active sites at atomic‐scale not only improves the atomic utilization, but also provides a well‐defined coordination structure for nanozymes’ catalytic mechanism research. Herein, a surfactant‐assisted method is reported for preparing 2D metal–organic frameworks based single zinc sites nanozyme (SZN‐MOFs) through assembling preformed Zn single‐atom coordinated porphyrin precursors into ultrathin MOF nanosheets. The Zn atom loading weight ratio in SZN‐MOFs is up to 4.6 wt.%. The SZN‐MOFs exhibit extraordinary peroxidase‐like activity, which can effectively catalyze H2O2 into hydroxyl radicals. The catalytical mechanism is elucidated and the origin of the high peroxidase‐like activity of SZN‐MOFs is rationalized using density functional theory calculations. Finally, it is demonstrated that the SZN‐MOFs present great promises for in vitro and in vivo antibiofilm activity under a low concentration of H2O2. This study not only develops a surfactant‐assisted method for fabricating MOF‐based single sites nanozyme, but also manifests the applications in the field of antibiofilm therapy.

Ultrathin ZIF‐8 Membrane through Inhibited Ostwald Ripening for High‐Flux C3H6/C3H8 Separation

AbstractMetal–organic frameworks (MOFs) are one of the most promising membrane materials for olefin/paraffin separations. However, most of MOF membranes have a thickness over 1 µm, which greatly compromises the permeation flux. While previous studies are focused on increasing crystal nucleus density on the substrates, achieving ultrathin membrane via modulation of the crystal growth is lacking. Herein, an inhibited Ostwald ripening (IOR) strategy is proposed to fabricate ultrathin ZIF‐8 membranes, through incorporating polymer‐based inhibitors into the membrane formula to inhibit the growth process of ZIF‐8 crystals via the metal–organic coordination. The IOR process can be readily tuned by varying the functional groups, molecular weights, and concentrations of the inhibitors, enabling a facile control over the IOR degree and thus the membrane thickness. Consequently, the thickness of ZIF‐8 membranes can be dramatically reduced to 180 nm. The resulting membranes exhibit ultrahigh C3H6/C3H8 separation performance with C3H6 permeance of 386 GPU and C3H6/C3H8 separation factor of 120. It is anticipated that this straightforward and efficient IOR strategy can open a new avenue for the fabrication of ultrathin MOF membranes to tackle many critical molecular separations.

Ultrathin trimetallic metal–organic framework nanosheets for accelerating bacteria-infected wound healing

Bacteria-infected wounds are commonly regarded as a hidden threat to human health that can create persistent infection and even bring about amputation or death. Two-dimensional metal–organic frameworks (2D MOFs) with biomimetic enzyme activity have been used to reduce the huge harm caused by antibiotic resistance due to their massive active sites and ultralarge specific surface area. However, their therapeutic efficiency is unsatisfactory because of their relatively low catalytic activity and poor productivity. In this paper, we presented a simple and mild one-pot solution phase method for the large-scale synthesis of NiCoCu-based MOF nanosheets. The NiCoCu nanosheets (denoted as (Ni2Co1)1-xCux) with controlled molar ratios have different morphologies and sizes. Specifically, the (Ni2Co1)0.5Cu0.5 nanosheets showed the best catalytic performance toward the reduction of H2O2 and H2O2 was efficiently catalyzed to generate toxic •OH in the presence of MOF nanosheets with peroxidase-like activity. (Ni2Co1)0.5Cu0.5 exhibited the best antibacterial activity against gram-positive Escherichia coli and methicillin-resistant Staphylococcus aureus bacteria. Animal wound healing experiments demonstrate that ultrathin trimetallic nanosheets can effectively contribute to wound healing with excellent biocompatibility. This study reveals the immense potential of ultrathin trimetallic MOF nanosheets for clinical antibacterial therapy for future pragmatic clinical applications.

Electrochemiluminescence resonance energy transfer system between ruthenium-based nanosheets and CdS quantum dots for detection of chlorogenic acid.

A new strategy is proposedfor ultrasensitive detection of chlorogenic acid (CGA) by fabricating an electrochemiluminescence resonance energy transfer (ECL-RET) sensing platform. Thenovel system designedby introducing ruthenium-based 2D metal-organic framework nanosheets (Ru@Zn-MOF) as ECL acceptor and L-cysteine capped CdS quantum dots (L-CdS QDs) as ECL donor, exhibited good ECL response. The possible mechanism of the modified electrode surface reaction was discussed. Modifying of the electrode surfaceby application of L-CdS QDs directly on ultrathin MOF nanosheets greatly shortened the electron-transfer distance and reduce energy loss, therefore significantly improving the ECL efficiency. The prepared sensor demonstrated good stability and highly selective detection of the target molecule. Under optimal conditions, the constructed sensor for the detection of CGA exhibited a wide linear range from 1.0 × 10-10 to 1.0 × 10-4mol·L-1 and a low detection limit of 3.2 × 10-11mol·L-1 with a correction coefficient of 0.995. Therecovery for spiked samples was calculated to be 94.4-109% and the RSD was 1.07-1.72% in real samples. The obtained sensor is considered to be a promising platform for CGA detection. Electrochemiluminescence resonance energy transfer (ECL-RET) sensing platform is used for the detection for chlorogenic acid.

Dual nanozyme based on ultrathin 2D conductive MOF nanosheets intergraded with gold nanoparticles for electrochemical biosensing of H2O2 in cancer cells

The development of facile, rapid and cost-effective strategies for sensitive detection of cancer biomarkers in human samples is of great significance for early diagnosis of malignant tumors related diseases. In this work, we develop a high-performance electrochemical biosensor based on highly active dual nanozyme amplified system, i.e., ultrathin two-dimension (2D) conductive metal–organic framework (C-MOF) nanosheets (NSs) decorated with high-density ultrafine gold nanoparticles (Au-NPs), and explore its application in sensitive detection of cancer biomarker H2O2 in live cells. The C-MOF NSs {i.e., Cu-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene)-NSs} provide large surface area and abundant active open metal sites (Cu–O4), which could improve the catalytic activity of Cu-HHTP-NSs towards H2O2. Moreover, abundant exposed O atoms also serve as anchor sites for the deposition of high-density ultrafine Au-NPs (∼3 nm) without agglomeration. Owing to the synergistic contributions of high catalytic activity of Cu-HHTP-NSs and Au-NPs as well as their unique structural and electrical properties, the as-prepared nanohybrid modified electrode exhibits good sensing performances to H2O2 with an extremely low detection limit of 5.6 nM (3σ rules) and a high sensitivity of 188.1 μA cm−2 mM−1. Furthermore, the proposed nanozymatic electrochemical biosensor has been applied in real-time tracking H2O2 released from different human colon cells to identify colon cancer cells from normal colon epithelial cell, which demonstrates its great prospect for early diagnosis and management of various cancer diseases.

Ultrathin two-dimensional nickel-organic framework nanosheets for efficient electrocatalytic urea oxidation

Synthesis of highly-efficiency electrocatalysts with controllable morphology, enriched active sites, and low cost is of great significance for urea oxidation reaction (UOR) applications. In this work, novel two-dimensional (2D) nickel-based metal-organic framework (Ni-MOF) nanosheets comprising Ni2+ and an organic ligand of 4-Dimethylaminopyridine (Ni-DMAP-t, where t is the synthesis time) are firstly synthesized by a facile one-pot solvothermal method. By thickness regulation of Ni-DMAP-t nanosheets, the self-supported Ni-DMAP-2 with the smallest thickness on Ni foam (Ni-DMAP-2/NF) exhibits high electrocatalytic activity toward UOR with a low potential of 1.45 V at a current density of 100 mA cm−2. Moreover, by further coupling with the cathodic hydrogen evolution reaction, the urea-assisted electrolytic hydrogen production system using Ni-DMAP-2/NF as anode displays a dramatic voltage reduction by 290 mV at a current density of 50 mA cm−2 as compared with that of conventional water electrolysis using the same electrodes. Such a superior UOR electrocatalytic activity of Ni-DMAP-2/NF is ascribed to the abundant Ni active sites exposed on the surface of Ni-DMAP-2, as well as the accelerated electron/ion transfer properties endowed by its ultrathin 2D nanosheets structure. This work offers some new ideas into the design and development of ultrathin 2D Ni-based MOF electrocatalysts for urea-related energy storage devices.

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.