Cu-based Metal-organic Framework Research Articles

Cu-based metal-organic framework HKUST-1 as effective catalyst for highly sensitive determination of ascorbic acid.

In this work, a Cu-based nanosheet metal–organic framework (MOF), HKUST-1, was synthesised using a solvent method at room temperature. Its morphology, structure and composition were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman spectroscopy, nitrogen adsorption and desorption isotherms, energy dispersive X-ray spectroscopy (EDS) and elemental analysis (EA). This material was then loaded onto the surface of an indium tin oxide (ITO) electrode to catalyse the electrochemical oxidation of ascorbic acid (AA). An equal-electron-equal-proton reaction was deduced from the pH investigation, and a diffusion-controlled process was reinforced by the dynamics study. Under optimal conditions, the oxidation peak current at +0.02 V displayed a linear relationship with the concentration of AA within the ranges of 0.01–25 and 25–265 mM, respectively. The limit of detection (LOD) was 3 μM at S/N of 3. The superb response could be ascribed to the porous nanosheet structure of HKUST-1, which enhanced both the effective surface area and the electron transfer ability significantly. Moreover, the novel AA sensor demonstrated good reproducibility, favourable stability and high sensitivity towards glucose, uric acid (UA), dopamine (DA) and several amino acids. It was also successfully applied to the real sample testing of various AA-containing tablets.

Cu-MOF derived Cu-C nanocomposites towards high performance electrochemical supercapacitors.

For the development of asymmetric supercapacitors with higher energy density, the study of new electrode materials with high capacitance is a priority. Herein, the electrochemical behavior of nano copper in alkaline electrolyte is first discovered. It is found that there are two obvious reversible redox symmetric peaks in the range of −0.8–0.2 V in the alkaline electrolyte, corresponding to the conversion of copper into cuprous ions, and then converting cuprous ions into copper ions, indicating that the nanocomposite electrode has the characteristics of a pseudocapacitive reaction. It has a specific capacitance of up to 318 F g−1 at a current density of 1 A g−1, which remains at nearly 100% after 10 000 cycles at the same current density. When assembled with a Ni(OH)2-based electrode into an asymmetric supercapacitor, the device shows excellent capacitive behavior and good reaction reversibility. At 0.4 A g−1, the supercapacitor delivers a reversible capacity of 8.33 F g−1 with an energy density of 13.5 mW h g−1. This study first discovers the electrochemical behavior of nano copper, which can provide a new research idea for further expanding the negative electrodes of supercapacitors with higher energy density.

CO2 capture ability of Cu-based metal-organic frameworks synergized with amino acid-functionalized layered materials

Metal-organic framework (MOF) materials have significant advantages for capturing CO2. To further improve the CO2 adsorption performance of MOFs, a compound material of l-arginine modified graphene oxide (GO) with MOFs (MOF/GO-Arg) was synthesized. Introduction of amino acid-functionalized lamellar GO into MOF material not only generated new pores at their interface to improve the adsorption of the MOF but also promoted the CO2 capture at low humidity. The structural and chemical properties of the parent components and composite materials were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption-desorption, thermal analysis and scanning electron microscopy (SEM). The dynamic CO2 adsorption properties of the materials were compared under different temperatures, flow rates and humidities. Three kinetic models were used to fit the adsorption curves of the as-synthesized adsorbents under different conditions, and then the optimal dynamic model was determined. Since the reusability of the adsorbents is especially important for the use of these materials in practice, the CO2 adsorption was repeated for 10 cycles under optimal temperature, flow rate and high humidity conditions.

A review on metal-organic frameworks for photoelectrocatalytic applications

Semiconductor-based photoelectrocatalytic processes have attracted considerable research interest for solar energy collection and storage. Photoelectrocatalysis is a heterogeneous photocatalytic process in which a bias potential is applied to a photoelectrode, and thus the photoelectrocatalytic performance is closely related to the photoelectrode prepared by semiconductors. Among various semiconductors, metal-organic frameworks (MOFs) have attracted more and more attention because of their unique properties such as optical properties and adjustable structure. Herein, a comprehensive review on different MOFs (Ti-based, Zn-based, Co-based, Fe-based, Cu-based, and mixed metal-based MOFs) for heterogeneous photoelectrocatalysis is carried out and, in particular, the application of this technique for CO2 conversion and water splitting is discussed. In addition, the challenges and development prospects of MOFs in photoelectrocatalysis are also presented.

Highly effective H2/D2 separation in a stable Cu-based metal-organic framework

A three-dimensional copper metal—organic framework with the rare chabazite (CHA) topology namely FJI-Y11 has been constructed with flexibly carboxylic ligand 5,5′-[(1,4-phenylenebis(methylene))bis(oxy)]diisophthalic acid (H4L). FJI-Y11 exhibits high water stability with the pH range from 2 to 12 at temperature as high as 373 K. Importantly, FJI-Y11 also shows high efficiency of hydrogen isotope separation using dynamic column breakthrough experiments under atmospheric pressure at 77 K. Attributed to its excellent structural stability, FJI-Y11 possesses good regenerated performance and maintains high separation efficiency after three cycles of breakthrough experiments.

AuNPs-NH2/Cu-MOF modified glassy carbon electrode as enzyme-free electrochemical sensor detecting H2O2

Hydrogen peroxide (H2O2) plays an important role in physiological processes. In this work, a Cu-based metal-organic framework (Cu-MOF) was synthesized under ionothermal condition, further grafted with ammoniated Au nanoparticles (AuNPs-NH2) to prepare AuNPs-NH2/Cu-MOF composite. Glassy carbon electrode (GCE) was modified with AuNPs-NH2/Cu-MOF to prepare AuNPs-NH2/Cu-MOF/GCE electrode, which was used in H2O2 detection. AuNPs-NH2/Cu-MOF/GCE exhibits itself as a highly sensitive and selective electrochemical enzyme-free sensor for H2O2 detection. A quantitative detection to H2O2 can be found with a wide linear response toward H2O2 concentrations ranging 5–850 μM, its limit of detection (LOD) is as low as 1.2 μM with a high sensitivity of 1.71 μA/cm2·μM. AuNPs-NH2/Cu-MOF/GCE sensor has been applied to determine H2O2 effectively in human cervical cancer cells by adding the ascorbic acid as the stimulant. Our work presented a AuNPs-NH2/Cu-MOF/GCE composite electrode which is a promising enzyme-free electrochemical sensor for quantitive H2O2 detection in human cervical cancer cells.

Bottom-Up Fabrication of 1D Cu-based Conductive Metal-Organic Framework Nanowires as a High-Rate Anode towards Efficient Lithium Storage.

Conductive metal-organic frameworks (MOFs), as a newly emerging multifunctional material, hold enormous promise in electrochemical energy-storage systems owing to their merits including good electronic conductivity, large surface area, appropriate pore structure, and environmental friendliness. In this contribution, a scalable solvothermal strategy was devised for the bottom-up fabrication of 1D Cu-based conductive MOF, that is, Cu3 (2,3,6,7,10,11-hexahydroxytriphenylene)2 (Cu-CAT) nanowires (NWs), which were further utilized as a competitive anode for lithium-ion batteries (LIBs). The intrinsic Li storage mechanism of the Cu-CAT electrode was also explored. Benefiting from its structural virtues, the resultant 1D Cu-CAT NWs were endowed with superb Li+ diffusion coefficients and electrochemical conductivities and exhibited remarkably high-rate reversible capacities of approximately 631 mAh g-1 at 0.2 A g-1 and even approximately 381 mAh g-1 at 2 A g-1 , along with striking capacity retention of 81 % after 500 cycles at 0.5 A g-1 . In addition, a Cu-CAT NWs-based full cell assembled with LiNi0.8 Co0.1 Mn0.1 O2 as the cathode displayed a large energy density of approximately 275 Wh kg-1 as well as excellent cycling behavior. These results manifest the promising application of 1D conductive Cu-CAT NWs in advanced LIBs and even other potential versatile energy-related fields.

Fine-Tuning the Pore Environment of the Microporous Cu-MOF for High Propylene Storage and Efficient Separation of Light Hydrocarbons.

Ethylene (C2H4) and propylene (C3H6) are important energy sources and raw materials in the chemical industry. Storage and separation of C2H4 and C3H6 are vital to their practical application. Metal–organic frameworks (MOFs) having adjustable structures and pore environments are promising candidates for C3H6/C2H4 separation. Herein, we obtained a Cu-based MOF synthesized by H3TTCA and pyrazine ligands. By adding different functional groups on the ligands within the MOFs, their pore environments are adjusted, and thus, the C3H6 storage capacity and C3H6/C2H4 separation efficiency are improved. Eventually, the fluoro- and methyl-functionalized iso-MOF-4 exhibits a better gas storage and C3H6/C2H4 separation performance compared with iso-MOF-1 (nonfunctionalized), iso-MOF-2 (fluoro-functionalized), and iso-MOF-3 (methyl-functionalized). A record-high C3H6 uptake of 293.6 ± 2.3 cm3 g–1 (273 K, 1 atm) is achieved using iso-MOF-4. Moreover, iso-MOF-4 shows excellent repeatability, and only 3.5% of C3H6 storage capacities decrease after nine cycles. Employing Grand Canonical Monte Carlo (GCMC) simulations, it is indicated that iso-MOF-4 preferentially adsorbs C3H6 rather than C2H4 at low pressure. Single-crystal X-ray diffraction on C3H6-adsorbed iso-MOF-4 crystals precisely demonstrates the adsorption positions and arrangement of C3H6 molecules in the framework, which is consistent with the theoretical simulations. Remarkably, gas sorption isotherms, molecular simulations, and breakthrough experiments comprehensively demonstrate that this unique MOF material exhibits highly efficient C3H6/C2H4 separation. Additionally, iso-MOF-4 also possesses efficient separation of C3H8/CH4 and C2H6/CH4, indicating its promising potential in storage/separation of light hydrocarbons in industry.

Selective aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran catalyzed by Cu-based metal organic frameworks with 2,2,6,6-tetramethylpiperidin-oxyl

Abstract While Cu combined with 2,2,6,6-tetramethylpiperidin-oxyl (TEMPO) constitutes a novel oxidative catalytic system using O2 for oxidation of 5-hydroxymethylfurfural (HMF), few studies have been conducted to investigate Cu/TEMPO/O2 for oxidation of HMF to 2,5-diformylfuran (DFF). More importantly, existing studies employ homogeneous Cu species, which is difficult for recovery; thus it is crucial to develop heterogeneous Cu catalyst incorporated with TEMPO for oxidation of HMF. Herein, a Cu-based metal organic frameworks (MOFs), HKUST-1, is proposed and employed for the first time as a heterogeneous catalyst with TEMPO for oxidative conversion of HMF to DFF in the presence of O2. Although TEMPO and HKUST-1 are ineffective separately for oxidation of HMF to DFF, the combination of HKUST-1 and TEMPO successfully converts HMF to DFF without by-products. The reaction duration could be as short as 3 h at 120 °C to achieve > 96% of HMF conversion with a selectivity > 99% and a yield of 96%, demonstrating that this HKUST-1+TEMPO+O2 is certainly promising and highly selective for HMF conversion to DFF. HKUST-1 is also reusable for incorporating with TEMPO to oxidize HMF to DFF. These results indicate that HKUST-1 is an advantageous heterogeneous catalyst for HMF conversion using TEMPO as an oxidant catalyst.

Tuning the Size and Shape of NanoMOFs via Templated Electrodeposition and Subsequent Electrochemical Oxidation.

The control over the size and shape of nanoMOFs is essential for their exploitation in integrated devices such as sensors, membranes for gas separation, photoelectrodes, etc. Here, we demonstrate the synthesis of nanowires and three-dimensionally interconnected nanowire networks of Cu-based metal-organic frameworks (MOFs) by a combination of ion-track technology and electrochemical methods. In particular, Cu nanowires and nanowire networks were electrodeposited inside polymeric etched ion-track membranes and subsequently converted by electrochemical oxidation into different Cu-based MOFs such as the well-known Cu3(BTC)2 (also known as HKUST-1) and the lesser-known MOF Cu(INA)2. The MOFs are formed inside the template, therefore adopting the shape of the host nanochannels. The synthesized MOF nanowires exhibit tunable diameters between 80 and 260 nm. Characterization by X-ray diffraction, thermogravimetric analysis/differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy indicates that the employed electrochemical conversion includes the formation of Cu2O as an intermediate, as well as the initial formation of an amorphous MOF phase, which crystallizes upon longer reaction times.

Strategy for Highly Sensitive Electrochemical Sensing: In Situ Coupling of a Metal-Organic Framework with Ball-Mill-Exfoliated Graphene.

A highly sensitive electrochemical sensing system is developed via in situ integration of Cu-based metal-organic frameworks (Cu-BTC, BTC = 1,3,5-benzenetricarboxylic acid) and high-conductivity ball-mill-exfoliated graphene (Cu-BTC@GS) by a simple method. The as-synthesized Cu-BTC@GS hybrids display remarkably enhanced electrochemical activity due to the synergistic effect resulting from the integration. Compared to those of the pristine GS, the introduction of Cu-BTC nanoparticles leads to significant improvement in the surface area and porosity, as revealed by the nitrogen adsorption-desorption analysis. In addition, the oxidation behavior of nicotinamide adenine dinucleotide studied using the rotating ring disk electrode further reveals a superior electron-transfer rate constant ( k) for the composite, indicating higher catalytic ability. Moreover, double potential step chronocoulometry of biomolecules (xanthine and hypoxanthine) and phenolic pollutants (bisphenol A and p-chlorophenol) reveals that the prepared composite possesses greatly enhanced adsorption properties, resulting in much higher response signals and detection sensitivity. Benefiting from the superior reactivity, a highly sensitive electrochemical sensing platform for wide targets is successfully fabricated. It was used in the analysis of plasma, urine, and receipt and wastewater samples, and the results were highly consistent with those obtained by high-performance liquid chromatography. We believe that this study provides an effective strategy for the construction of high-performance electrochemical sensing systems.

Electrocatalysis of the first electron transfer in hydrogen evolution reaction with an atomically precise CuII-organic framework catalyst

Developing atomically precise catalysts for hydrogen evolution reaction (HER) will help understand the catalytic reaction mechanisms for guiding the synthesis of new HER catalysts. A Cu-based metal-organic framework (CuII-MOF) consisting of trinuclear mixed-ligand units was prepared under hydrothermal conditions, and the structure, morphology, and elemental composition were characterized by (single crystal) XRD, TEM, SEM, XPS, BET, TGA and ATR-FTIR. Doping of 9.2 wt% CuII-MOF powder into the carbon paste electrode caused a roughly 440 mV positive shift of the HER potential at 10 mA cm−2 in 1.0 M H2SO4. The CuII-MOF showed a high working stability due to the dual-ligand-protected Cu active centers. The intrinsic catalytic mechanism was investigated by Tafel slope analysis, solid state electrochemistry and electrochemical impedance spectroscopy. The CuII ions in the CuII-MOF are successively reduced through two single-electron steps over a potential range of 0.7 to 0.1 V vs. RHE to form single-atom Cu0 active centers, on which adsorbed H atoms can be generated with a positive onset potential of about 100 mV vs. RHE through a following chemical redox reaction. The mechanistic findings point out the necessity and feasibility of developing bicomponent or bifunctional MOF-based catalysts to efficiently accelerate both the first and second electron transfer steps of HER.

Polythiophene Doping of the Cu-Based Metal-Organic Framework (MOF) HKUST-1 Using Innate MOF-Initiated Oxidative Polymerization.

The copper-based metal-organic framework (MOF) HKUST-1 adsorbs organic molecules into its pores. When loaded with electron-rich oligothiophenes, the resulting system reacts under heat to initiate oxidative polymerization without the use of any other oxidant or catalyst. This reaction is not observed in the non-redox-active MOF MIL-100(Al). We have characterized the composites by optical and nanoscale microscopy, vibrational and UV-vis spectroscopy, X-ray photoelectron spectroscopy, N2 sorption analysis, and thermogravimetric analysis/residual gas analysis. Unsubstituted oligothiophenes polymerize within MOF pores, while 3,4-ethylenedioxythiophene forms a coating on the MOF surface. MOF composites with conjugated polymer dopants trapped inside their pores undergo profound shifts in the composite electronic structure. Reasoning from time-dependent density functional theory calculations of an HKUST-1 model system bound to monomers, we rationalize the observed reactivity and propose an initiation mechanism based on a ligand-to-metal charge-transfer state.

Au/ERGO nanoparticles supported on Cu-based metal-organic framework as a novel sensor for sensitive determination of nitrite

In this work, an electrode which comprises Au nanoparticles (AuNPs) and electrochemically reduced graphene oxide (ERGO) recombined Cu based metal-organic framework (Cu-TDPAT) was prepared for nitrite detection. The structure and constituent of the modified material were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and FT-IR. The electrochemical behavior of nitrite at the modified electrode was performed by cyclic voltammetry and electrochemical impedance spectroscopy. The results indicated that the oxidation process of nitrite happened at recommended electrode had a superior response. The proposed electrode showed high electrocatalytic capacity toward nitrite oxidation with a wide linear working range (0.001–1000 μmol·L−1) and a detection limit of 0.006 μmol·L−1. Finally, the sensor was successfully applied to detect nitrite in real sample and achieved desirable recovery rate, showing its potential application in real-time detection of food.

Determination of Malachite Green in Fish by a Modified MOF-Based Electrochemical Sensor

Cu-based metal-organic frameworks modified by silver (Ag/Cu-MOFs) were in situ fabricated through a one-step direct synthesis. The as-prepared mixed-node MOFs were modified on glassy carbon (GC) electrode, which was utilized as a voltammetric sensor for probing malachite green. Compared with the bare GC electrode, the introduced Ag/Cu-MOF film on the electrode surface dramatically improved the sensitivity of the sensor response according to the accumulation and catalytic activity of Ag/Cu-MOFs for malachite green. The developed electrochemical sensor exhibited a low detection limit of 2.2 nM with a wide linear range of 10–140 nM and high anti-interference ability. The feasibility of the assay was verified by test of malachite green in fish sample. The proposed strategy presents valuable information for the evaluation of the food safety in aquaculture industry.

Control of structural flexibility of layered-pillared metal-organic frameworks anchored at surfaces

Flexible metal-organic frameworks (MOFs) are structurally flexible, porous, crystalline solids that show a structural transition in response to a stimulus. If MOF-based solid-state and microelectronic devices are to be capable of leveraging such structural flexibility, then the integration of MOF thin films into a device configuration is crucial. Here we report the targeted and precise anchoring of Cu-based alkylether-functionalised layered-pillared MOF crystallites onto substrates via stepwise liquid-phase epitaxy. The structural transformation during methanol sorption is monitored by in-situ grazing incidence X-ray diffraction. Interestingly, spatially-controlled anchoring of the flexible MOFs on the surface induces a distinct structural responsiveness which is different from the bulk powder and can be systematically controlled by varying the crystallite characteristics, for instance dimensions and orientation. This fundamental understanding of thin-film flexibility is of paramount importance for the rational design of MOF-based devices utilising the structural flexibility in specific applications such as selective sensors.

Development of gelatin microsphere encapsulated Cu-based metal-organic framework nanohybrid for the methotrexate delivery

The purpose of the study is to the effective approach for the development of methotrexate (MTX) loaded as an anticancer drug into Cu-based metal-organic framework nanohybrid (Cu-MOF/MTX) inserted in pH-sensitive gelatin microsphere biopolymer (Cu-MOF/MTX@GM). MTX was loaded into two-dimensional tunnels and the empty face-centered cubic lattice of Cu-MOF porous. The developed Cu-MOF/MTX@GM was characterized using FTIR, SEM, and XRD analysis. In vitro drug release was demonstrated through the comparison of the simulated physiological conditions and tumor tissue environment for illustrating the MTX release ability of the obtained novel microspheres. Furthermore, the cytotoxicity of the MTX-loaded Cu-MOF @GM is examined by MTT assay using the human breast epithelial adenocarcinoma (MCF-7) cell lines, and the results revealed that the carrier was suitable as an anticancer drug targeting. According to the obtained results, the developed carrier has promising qualities as an excellent candidate for target delivery of MTX to cancer tissues.

A vertically aligned CuO nanosheet film prepared by electrochemical conversion on Cu-based metal-organic framework for non-enzymatic glucose sensors

Constructing self-supported nanostructures on conductive substrates is an effective strategy to achieve non-enzymatic glucose sensors that possessing good reusability, reproducibility and stability. In the present study, vertical aligned CuO nanosheets on Cu foam are prepared with an in-situ electrochemical process including Cu-based metal-organic framework growing and subsequent electrochemical conversion. The scanning electron microscope results reveal that the totally electrochemical preparation guarantees the CuO nanosheets homogeneously free-standing on the Cu foam. The vertical aligned architecture endows the CuO/Cu electrodes good performances when using them as non-enzymatic glucose sensors, including a detection limit of 330 nM and a sensitivity of 33.95 mA cm−2 mM−1. We suggest that the facilitated ion transport in the vertical aligned architecture and the good conductivity originated from the totally electrochemical synthesis are responsible for the marked performances. More importantly, the good controllability of electrochemical preparation leads to remarkable reusability, reproducibility and stability of the electrodes, verified by multi-test of one electrode, consistency of multi-electrode and periodic test of one electrode in a long term. The practical detection of CuO/Cu electrodes on serum samples indicates the results are basically consistent with the clinical reports from hospital, further indicating their attractive potential in practical application.

An electrochemical ratiometric sensor based on 2D MOF nanosheet/Au/polyxanthurenic acid composite for detection of dopamine

In this study, a novel Cu-based metal−organic frameworks (Cu-MOFs) composite material was prepared, and used to develop a sensitive and efficient electrochemical ratiometric sensor for dopamine detection. Gold nanoparticles (NPs) and the conductive poly(xanthurenic acid) p(XA) were assembled on the Cu-tetrakis (4-carboxyphenyl) porphyrin (TCPP) surface by electrodeposition and cyclic voltammetry (CV) method, which greatly improved the electrocatalytic performance of the Cu-MOF modified electrode. Two substances (dopamine/DA, paracetamol/PA) with different electrochemical peaks were added to the electrolyte solutions, where DA was the analyte and PA was as a reference. The ratiometric value of differential pulse voltammetry (DPV) oxidation current (IDA/IPA) linearly increased with the increasing concentration of DA with low detection limit. This electrochemical ratiometric approach based on the metal−organic framework composites is expected to be a valuable strategy for detection of other analytes.

The Fabrication of 2D Cu-Based MOF Nanosheets for DNA Detection

The Cu-based metal–organic framework (MOF) analogues, copper 1,4-benzenedicarboxylate (CuBDC), copper 2,6-naphthalenedicarboxylate (Cu(2,6-NDC)), and copper 1,4-naphthalenedicarboxylate (Cu(1,4-NDC)) MOF nanosheets, are prepared as biosensor nanoplatforms for DNA detection by a spray method. With the ultrathin 2D structure, the fabricated MOF nanosheets exhibited better detection of target DNA, in particular when compared with the corresponding 3D MOF bulky crystals, when used as a DNA biosensor platform. The Cu(1,4-NDC) nanosheets display a distinct sensitivity with a detection limit of 0.3nM and linear range of 0–20nM, and selectivity for the target DNA or target DNA mixture. The feasible biosensor nanoplatform composed of 2D MOF nanosheets broadens the application scope of MOF nanosheets.