Dual Metal-organic Frameworks Research Articles

Fe2O3@ZrO2 catalyst derived from MOF-on-MOF for direct CO2 hydrogenation to light olefins

The utilization of CO2 for the production of light olefins through catalysis with iron-based catalysts presents a viable strategy to address the challenges of carbon neutrality. In this study, we synthesized a novel hybrid catalyst Fe2O3@ZrO2, derived from the pyrolysis of dual metal–organic frameworks (NH2-MIL-88B@UiO-66). Under specific conditions (340 °C, 3.0 MPa, CO2/H2 = 1:3, 10000 mL gcat−1h−1), the Fe2O3@ZrO2 catalyst exhibited a notable space–time yield of light olefins at 12.7 mmol g−1h−1. The characterizations results show an electron transfer from ZrO2 to the Fe2O3 surface was observed at the heterointerface of Fe2O3 and ZrO2. This electron transfer mechanism was identified as advantageous for the formation of the active phase Fe5C2. This research introduces an innovative use of the hybrid Fe2O3@ZrO2 catalyst derived from MOF-on-MOF, holding significant promise in advancing the field of CO2 hydrogenation catalysts.

Collaborative role of co-doping and surface modifying for adjusting surface state of hematite to release the photoelectrochemical activity

Inhibition of bulk and interfacial charge carrier recombination is an urgent solution to release furthest the photoelectrochemical potential abilities of hematite photoelectrode. Herein, the Zr-Y dual metal co-doping engineering and Co/Fe dual metal-organic frameworks cocatalyst layer were employed for modifying hematite photoanode. The novel CoFe-MOF/Zr-Y:Fe2O3 nanoarray composite photoanode exhibits higher PEC activity, the photocurrent density at 1.23 V vs.RHE is increased by 4.7 times than that of the pristine α-Fe2O3. The gain in bulk charge separation efficiency was mainly attributed to the synergistic effect between the two doping ions to improve the electrical conductivity. Wherein, Zr4+ doping endows more free electrons in the bulk α-Fe2O3 and Y3+ introduction causes polaron mobility enhancement. For another, co-doping could reduce the recombination surface state, but form the intermediate surface state to promote hole transfer, thus effectively inhibiting the severe recombination of photogenerated electrons and holes. Furthermore, the CoFe-MOF cocatalyst coating with abundant active sites not only expedites the oxygen evolution reaction kinetics process, but also passivates the surface hole trapping state more thoroughly, resulting in efficient interfacial hole transfer and utilization. This work affords a new collaborative role of co-doping and surface modifying effective avenue for adjusting surface state of hematite to release the photoelectrochemical activity.

Fluorescence turn off-on continuous response of dual lanthanide metal organic frameworks for selective detecting fluoroquinolone antibiotics

Eu3+ and Tb3+ as central ions and 1,4-phthalic acid (H2BDC) as ligand, a dual lanthanide metal-organic framework, Eu-Tb(BDC), was synthesized by co-precipitation method. The products performed stable crystal structure and adjustable fluorescence color. Eu0.15Tb2.85 (BDC) 3.0 was selected as an optimized probe to detect norfloxacin (NFX) in urine, and the fluorescence color was found to transfer from bright yellow to dark cyan and then to strong green with increasing NFX concentration. Mechanism analysis revealed that NFX with low concentration (10−6-10−3 M) stimulated light competition with BDC ligand due to internal filtration effect (IFE), resulting in the gradual fluorescence shutdown of Eu3+and Tb3+. While further increasing concentration of NFX to 10−3-10−2 M, the antibiotic molecules coordinated with lanthanide ions and transitioned their role from competitor to assistant. Where the energy transfer due to antenna effect overwhelmed IFE, the exciting light energy were retransferred to Eu3+ or Tb3+, and the probe's fluorescence restored. Generally, the Eu-Tb(BDC) probe performed fluorescence turn off-on response to norfloxacin with continuous concentration changing. Additionally, when detecting other fluoroquinolone antibiotics, the fluorescence of Eu0.15Tb2.85(BDC)3.0 changed from bright yellow to bright blue and eventually to dark red, which was attributed to the different coordination degrees of various antibiotic molecule with Tb3+ and Eu3+. It can be used to distinguish norfloxacin from other fluoroquinolone antibiotics.

CdS Nanoparticles Supported on a Dual Metal–Organic Framework as a Catalyst for the Photodegradation of Tetracycline

CdS Nanoparticles Supported on a Dual Metal–Organic Framework as a Catalyst for the Photodegradation of Tetracycline

Mn-Fe dual metal-organic framework based on trimesic acid as a high-performance electrode for lithium metal batteries.

A novel Mn-Fe dual metal-organic framework (Mn-Fe-BTC DMOF) was synthesized via a one-step hydrothermal method and employed as a cathode material in lithium metal batteries. The Mn-Fe-BTC DMOF exhibited a high initial capacity (1385 mA h g-1) and after 100 cycles (687 mA h g-1), demonstrating its potential for high-performance energy storage devices.

Ultrathin 2D Pd/Cu Single-Atom MOF Nanozyme to Synergistically Overcome Chemoresistance for Multienzyme Catalytic Cancer Therapy.

Single-atom nanozymes (SAzymes) have obtained increasing interest to mimic natural enzymes for efficient cancer therapy, while challenged by chemoresistance from cellular redox homeostasis and the interface of reductive species in tumor microenvironment (TME). Herein, a dual single-atomic ultrathin 2D metal organic framework (MOF) nanosheet of multienzyme (Pd/Cu SAzyme@Dzy) is prepared to synergistically overcome chemoresistance for multienzyme enhanced cancer catalytic therapy. The Pd SAzyme exhibits peroxidase (POD)-like catalytic activity for overcoming chemoresistance via disturbing cellular redox balance. This is further enhanced by cascade generation of more ∙OH via Cu+ -catalyzed POD-like reactions, initiated by in situ-reduction of Cu2+ into Cu+ upon GSH depletion. This process can also avoid the consumption of ∙OH by endogenous reductive GSH in TME, ensuring the adequate amount of ∙OH for highly efficient therapy. Besides, the DNAzyme is also delivered for gene therapy of silencing cancer-cell-targeting VEGFR2 protein to further enhance the therapy. Based on both experiments and theoretical calculations, the synergetic multienzyme-based cancer therapy is examined and the enhancement by the cascade tumor antichemoresistance is revealed.

Spatial charge separation in core-shell dual metal-organic frameworks for enhanced CO2 photoreduction

Flexibly and controllably regulating the functionality of the core–shell system is still challenging, which is largely determined by the shell thickness and core–shell interface. Here, elaborately designed core–shell dual MOFs were constructed via in-situ growth of Cu-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) shell with adjustable thicknesses over CuFe Prussian blue analogue (PBA). The thin-shell CuFe PBA@Cu-HHTP heterojunction (CFH-1) improves charge separation and transfer compared to CuFe PBA and thick-shell heterojunction. Density functional theory results indicate the efficient regulation of electron density near Cu site via constructing heterojunction. The photocatalytic CO2-to-CO activity of CFH-1 is improved (29.3 μmol·g−1) by ∼ 14 times than pristine CuFe PBA. This study provides information on charge separation at the core–shell structure interface to achieve efficient photocatalytic CO2 conversion.

Dual Ni/Co-hemin metal–organic framework-PrGO for high-performance asymmetric hybrid supercapacitor

In this study, we conducted direct synthesis of a dual metal–organic framework (Ni/Co-Hemin MOF) on phosphorous-doped reduced graphene oxide (PrGO) to serve as an active material in high-performance asymmetrical supercapacitors. The nanocomposite was utilized as an active material in supercapacitors, exhibiting a noteworthy specific capacitance of 963 C g−1 at 1.0 A g−1, along with a high rate capability of 68.3% upon increasing the current density by 20 times, and superior cycling stability. Our comprehensive characterization and control experiments indicated that the improved performance can be attributed to the combined effect of the dual MOF and the presence of phosphorous, influencing the battery-type supercapacitor behavior of GO. Additionally, we fabricated an asymmetric hybrid supercapacitor (AHSC) using Ni/Co-Hemin/PrGO/Nickel foam (NF) and activated carbon (AC)/NF. This AHSC demonstrated a specific capacitance of 281 C g−1 at 1.0 A g−1, an operating voltage of 1.80 V, an impressive energy density of 70.3 Wh kg−1 at a high power density of 0.9 kW kg−1. Notably, three AHSC devices connected in series successfully powered a clock for approximately 42 min. These findings highlight the potential application of Hemin-based MOFs in advanced supercapacitor systems.

Dual-ligand Cu-based MOFs for electrocatalytic reduction of NO3–

Electrocatalytic nitrate reduction reaction (ENRR) to recyclable NH3 or environmental-friendly N2 is a sustainable technology. In this study, we prepared three dual ligand Cu-based metal organic framework (Cu@MOFs) for efficient ENRR. The batch ENRR test revealed that Cu-bip-BTC exhibited the best performance in terms of NH3-N selectivity (61.64%), NH3-N yield (12.09 ×103 µgCu·h–1 mg–1) and faradaic efficiency for NH3 (80.97%) at −0.58 V vs. RHE. The ligands and coordination of Cu@MOFs affect the electronic structure of Cu and the adsorption performance of NO3–, leading to differences in the performance of the electrocatalytic reduction of nitrate. The quenching experiment of tert-butanol (TBA) demonstrates that NO3– is directly reduced by electrons on Cu@MOFs at −0.58 V, and in-situ spectrometric analysis identified the intermediates and pathways of ENRR. Cu-bip-BTC has the highest NH3-N selectivity due to its faster kinetic reaction rate, stronger inhibition of the hydrogen evolution reaction, and higher NO3– adsorption energy. In addition, ENRR combined with breakpoint chlorination reactions suggests that achieving nitrogen elimination is feasible, and this study provides a strategy for the application of dual-ligand Cu-based MOFs in ENRR.

MnCoOx@Graphene Derived from Dual MOFs as Superior Anode for Lithium Ion Batteries

The MnCoOx@RGO derived from dual metal organic framework (MOF) were synthesized via a simple solvothermal method followed by the heat treatment. While measured as anode for lithium ion batteries (LIBs), this MnCoOx@RGO nanocomposite exhibit an initial discharge capacity of 1548 mAhg−1 at 100 mAg−1, and an good reversible capacity of 815 mAhg−1 after 150 cycles. The remarkable lithium storage performance of the nanocomposite is attributed to the synergistic interaction between Mn and Co, the mesoporosity structure, and the conductive reduced graphene oxide (RGO) support, which can shorten the difffusion paths of both Li+ and charge carriers and effectively buffer the volume change during the Li+ insertion/extraction process.

Design of ZnIn2S4@N−Fe3C Nanorods‐Embedded Nanocages Assemblies for Efficient Photocatalytic Hydrogen Generation

AbstractCocatalyst materials can promote the separation of photogenerated electron‐hole pairs and accelerate the catalytically active sites of semiconductor photocatalysts. However, it is critical to make low‐cost, noble‐metal‐free materials with high catalytic reactivity, yet this task is extremely difficult to do. Herein, an effective photocatalytic hydrogen generation process has been developed using N‐doped Fe3C (N−Fe3C) nanocages adorned with ultrathin ZnIn2S4 nanosheets produced from a dual metal organic framework. In addition, the highly porous hybrid structure developed gives a large number of active sites for catalytic reduction events, and light scattering can be used to better capture visible light. Due to their improved solar‐driven hydrogen evolution rate (9,600 μmol h−1 g−1) and apparent quantum efficiency (3.6 %), these structures are superior to those of Pt noble‐metal co‐catalytic systems and ZnIn2S4‐based nanohybrids, which were previously reported.

A sandwich electrochemical immunosensor based on MXene@dual MOFs for detection of tumor marker CA125.

The detection signal of carbohydrate antigen 125 (CA125) can be quantitatively amplified via the dual metal-organic framework (MOF) sandwich strategy. We propose a versatile method for synthesizing uniform MXene and MIL-101(Fe)-NH2 composites that combine the advantages of both materials to build a base layer with superb performance. MXene exhibits excellent electrical conductivity and high surface area. The mesoporous MIL-101(Fe)-NH2 not only increases the loading capacity of the primary antibody but also possesses the catalytic activity of the metal center (Fe). UiO66 loaded with methylene blue (MB) was fabricated as an electrochemical immunosensor signal tag to enable the detection of CA125. The mixture of MXene and MIL-101(Fe)-NH2 prepared as the substrate was fixed by chitosan rich in amino groups. As the signal amplification sector, UiO66@MB enhanced secondary antibody loading capacity and generated a redox signal enabling the detection of antigenic substances. The proposed electrochemical immunosensor demonstrated high sensitivity with a low limit of detection (LOD) of 0.006 U/mL. Therefore, the dual MOF sandwich-based immunosensor provides a novel method for the early diagnosis of CA125.

MIL-68 (In) and ZIF-8 assisted construction of n-n heterostructure for the effective sensing of trace-level ozone

The crucial challenge to exploit effective ozone (O3) gas sensors lies in developing novel functional sensing materials to meet the requirement of trace-level detection threshold (50 ppb). Metal oxide semiconductors (MOSs) with controllable heterogenous composites as high-performance sensing layers are expected to break through this bottleneck. This work proposes the hybridization of MIL-68 (In) and ZIF-8, which are employed as dual metal organic frameworks (MOFs) sacrificial templates to design n-n heterostructures. The derived In2O3 backbone showed a hexagonal prismatic structure with a large aspect ratio. The robust architecture enabled the uniform decoration of mass of ZnO nanoparticles (NPs) on the surfaces without the damage of high porosity for the gas diffusion. Consequently, the optimal sensor with appropriate ZnO NPs loading amount exhibited trace O3 detection ability as low as 15 ppb, which was attributed to the smart design of n-n heterostructure, rich active sites and improved oxygen-adsorbing capacity. Thus, this work inspires a new way to utilize the versatile dual MOFs template for constructing heterogenous composites as O3 sensing materials.

Boosting the Adsorption Performance of Thiophenic Sulfur Compounds with a Multimetallic Dual Metal-Organic Framework Composite.

Adsorptive desulfurization over metal-organic frameworks (MOFs) remains a challenge in maintaining good performance in the presence of water. Herein, multimetallic Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) is first achieved through phase-competition-driven growth technology. The adsorption performance of thiophene (Th), benzothiophene (BT), and dibenzothiophene (DBT) in model fuels is systematically investigated at mild temperature and follows the order Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) > MOF-5 > MIL-88B. Excellent adsorptive activity is mainly ascribed to the associative effects of multimetal active sites, suitable pore sizes and shapes, acid-base interactions, and complexation. Meanwhile, MIL-88B exhibits a "brick-wall" effect and effectively enhances the water stability of Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) more than does MOF-5. Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) exhibits superior stability even after being immersed in water for 5 days, maintaining 77, 77, and 81% of the initial DBT, BT, and Th uptake capacities. After five periods of regeneration, more than 90% of the desulfurization capacity of Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) was recovered. This work provides a new strategy for the synthesis of desirable MOF-on-MOF, promoting its potential application to adsorption desulfurization.

Dual-metal-organic-framework derived CoP/MoP hybrid as an efficient electrocatalyst for acidic and alkaline hydrogen evolution reaction

Searching for efficient and cost-effective electrocatalysts for hydrogen evolution reaction (HER) is significantly desirable and challenging. Herein, N, P co-doped carbon-encapsulated CoP/MoP hybrid (CoP/MoP@NPC) is fabricated using dual-metal–organic-framework (dual-MOF) as precursor by a simple one-step phosphating process. When applied as an electrocatalyst toward the HER, the as-designed CoP/MoP@NPC hybrid shows efficiently catalytic performance with a lower overpotential of 183 mV to deliver a current density of 10 mA cm−2, smaller Tafel slope of 53.3 mV dec-1 as well as long-time stability for 10 h in 0.5 M H2SO4 owing to the distinctive component and structural advantages. Furthermore, the electrode material also displays enhanced electrocatalytic HER activity in alkaline media. Importantly, this work provides an effective and feasible route for the construction of bimetallic phosphide electrocatalysts toward hydrogen production.

A dual purpose aluminum-based metal organic framework for the removal of chloramphenicol from wastewater

The presence of antibiotics in the aquatic environment can cause significant environmental and human health problems even at trace concentrations. Conventional treatment systems alone are ineffective in removing these resistant antibiotics. To address this problem, oxidation and adsorption techniques were used to explore the removal of recalcitrant antibiotic chloramphenicol (CAP). An aluminum-based metal-organic framework (Al-MIL) with high surface area and extended porosity, was prepared and used both as adsorbent and catalyst for the oxidation of CAP. Characterization of the Al-MIL revealed a large surface area of 1137 m2 g−1, a homogeneous microporous structure, good crystallinity, and particle size in the range of 200–400 nm. Adsorption of CAP on Al-MIL achieved equilibrium after 1 h, reaching a maximum adsorption capacity of 96.1 mg g−1 at the optimum pH value of 5.3. The combination of adsorption and oxidation did not improve the % TOC reduction considerably, indicating an antagonistic rather than synergistic effect between the two processes. Oxidation alone in the presence of persulfate, achieved a % TOC reduction of 71% after 2 h, compared to 56% achieved by adsorption alone at the same duration. The optimum persulfate concentration was determined as 2.5 mM. The Al-MIL structure did not demonstrate any substantial deterioriation after six repeated runs, according to the reusability experiments.

Highly dispersed Co/Fe bimetal in carbonaceous cages as heterogeneous Fenton nanocatalysts for enhanced sulfamethoxazole degradation

A self-assembly strategy was presented for the synthesis of highly dispersed Co/Fe bimetallic carbon cages (CoFe50@C) through thermal morphology-controlled transformation of Fe doping dual metal-organic frameworks (MOFs). Taking advantage of the well dispersibility, synergetic effects between Fe and Co species, and enhanced graphitization degree of carbon, CoFe50@C exhibited a high removal efficiency of 98% in 180 min for sulfamethoxazole (SMX). The synergistic effect between Co and Fe species played an important role in promoting the reduction of Co(III) to Co(II) and the adsorption of H2O2 molecules, thus enhancing the generation of hydroxyl radicals (HO•), which had been demonstrated by density functional theory (DFT) calculations. Meanwhile, the graphitized carbon cages could prevent the loss of bimetallic active component and promote the electron transfer during catalytic reaction. This work provides a new type of highly dispersed Co/Fe bimetal carbon cages as heterogeneous Fenton nanocatalyst for the degradation of organic contaminants.

CeO2 Nanoparticles Boosted Fe‐N‐C Sites Derived from Dual Metal Organic Frameworks toward Highly Active and Durable Oxygen Reduction Reaction

AbstractThe durability improvement of Fe‐N‐C electrocatalysts toward acidic oxygen reduction reaction (ORR) remains a grand challenge. H2O2 seriously degrades Fe‐N‐C sites, which account for a major origin of the low durability. Herein, the growth of hemin decorated zeolitic imidazole framework (hemin‐ZIF 8) on preformed Ce‐1,3,5‐benzenecarboxylic acid (Ce‐BTC) metal organic frameworks (MOFs) is reported. Interestingly, the resultant dual MOFs appear to be Ce‐BTC nanorods decorated with many hemin‐ZIF 8 dodecahedral nanocrystals, well resembling rice panicles. After pyrolysis, CeO2 nanoparticles are evenly distributed in carbonized nanorods and abundant Fe‐N‐C sites are embedded in shrunk dodecahedra, labeled as Fe‐N‐C‐CeO2. Fe‐N‐C‐CeO2 exhibits a high ORR activity in terms of a half wave potential (E1/2) of 0.800 V (vs RHE). The high ORR activity is closely correlated with the well exposure of Fe‐N‐C sites. In addition, the presence of CeO2 leads to a low H2O2 yield of Fe‐N‐C‐CeO2 (2.3%), much lower than that of Fe‐N‐C (4.3%) by itself in the absence of CeO2. After 5000 potential cycling, the E1/2 of Fe‐N‐C‐CeO2 degrades 15 mV superior to that of Fe‐N‐C (42 mV). Moreover, a single cell with Fe‐N‐C‐CeO2 as cathode degrades much slower than that of Fe‐N‐C (28 000 s vs 7200 s) during chronoamperometric measurements.

Electronic Tuning of Core-Shell CoNi Nanoalloy/N-Doped Few-Layer Graphene for Efficient Oxygen Electrocatalysis in Rechargeable Zinc-Air Batteries.

The discovery of highly efficient, durable, and affordable bifunctional ORR/OER electrocatalysts is of great significance for the commercialization of rechargeable metal-air batteries. Herein, we synthesized uniformly sized CoNi alloy nanoparticles encapsulated with N-doped few-layer graphene (N-FLG) sheets via pyrolysis of a CoNi dual metal-organic framework precursor. The developed CoNi/N-FLG catalyst exhibited excellent oxygen reduction activity (comparable to a commercial 20 wt % Pt/C catalyst) and outstanding oxygen evolution activity (superior to a commercial 20 wt % IrO2/C catalyst), thus enabling efficient bifunctional oxygen electrocatalysis and stability when applied in prototype rechargeable zinc-air batteries. The remarkable electrochemical properties of CoNi/N-FLG originate from its unique core-shell structure and favorable electron penetration effects, thereby optimizing the adsorption/desorption strengths of intermediates formed during the oxygen reduction and oxygen evolution reactions.

Synthesis of a Dual Metal–Organic Framework Heterostructure as a Fluorescence Sensing Platform for Rapid and Sensitive Detection of Tetracycline in Milk and Beef Samples

Synthesis of a Dual Metal–Organic Framework Heterostructure as a Fluorescence Sensing Platform for Rapid and Sensitive Detection of Tetracycline in Milk and Beef Samples