MOF-derived Metal Research Articles

MOF-derived metal oxides with hollow porous nanocube structure realize ultra-wideband, lightweight, and anticorrosion microwave absorber

High density, skin effect, and environmental instability are significant limitations that restrict the application of metal-based microwave absorbers in achieving lightweight, high performance, and long service life. This study broke from traditional methods for preparing a microwave absorber Mn2O3-Fe3O4@PPy (polypyrrole) by employing an innovative annealing process to convert metal into metal oxide by the introduction of metal organic framework (MOF), which effectively achieving a more lightweight absorber material with hollow porous nanocube structure. Subsequently, PPy was coated onto the metal oxide surface to form a core-shell structure by a situ chemical oxidation synthesis method. The combination of metal oxide of the hollow porous nanocube structure and the core-shell structure formed by highly conductive PPy shell significantly enhanced heterogeneous interfaces and electromagnetic (EM) wave reflection. Excellent dielectric loss and impedance matching contributed evidently to the ultra-wideband EM wave absorption performance. It was demonstrated that, with a filling amount of only 20 wt%, the prepared Mn2O3-Fe3O4@PPy achieved an effective bandwidth (EAB) of 10.0 GHz at a thickness of 3.08 mm, with EABmax reaching 13 GHz. At a filling amount of only 10 wt%, the reflection loss (RL) was −62.13 dB, achieving an EAB of 7.4 GHz at 2.98 mm thickness, with EABmax reaching 11.4 GHz. Furthermore, the proposed strategy incorporating metal oxide and PPy enhanced corrosion resistance with higher charge transfer resistance.

Structural Reconstruction of a Cobalt- and Ferrocene-Based Metal-Organic Framework during the Electrochemical Oxygen Evolution Reaction.

Metal-organic frameworks (MOFs) are increasingly being investigated as electrocatalysts for the oxygen evolution reaction (OER) due to their unique modular structures that present a hybrid between molecular and heterogeneous catalysts, featuring well-defined active sites. However, many fundamental questions remain open regarding the electrochemical stability of MOFs, structural reconstruction of coordination sites, and the role of in situ-formed species. Here, we report the structural transformation of a surface-grown MOF containing cobalt nodes and 1,1'-ferrocenedicarboxylic acid linkers (denoted as CoFc-MOF) during the OER in alkaline electrolyte. Ex situ and in situ investigations of CoFc-MOF film suggest that the MOF acts as a precatalyst and undergoes a two-step restructuring process under operating conditions to generate a metal oxyhydroxide phase. The MOF-derived metal oxyhydroxide catalyst, supported on nickel foam electrodes, displays high activity toward the OER with an overpotential of 190 mV at a current density of 10 mA cm-2. While this study demonstrates the necessity of investigating structural evolution of MOFs during electrocatalysis, it also shows the potential of using MOFs as precursors in catalyst design.

Al-Based MOF-Derived Amorphous/Crystalline Heterophase Cobalt Sulfides as High-Performance Supercapacitor Materials.

Transition metal sulfides (TMSs) are promising electrode materials due to their high theoretical specific capacitance, but sluggish charge transfer kinetics and an insufficient number of active sites hamper their applications in supercapacitors. In this work, a self-sacrificial template strategy was employed to construct Al-based MOF-derived metal sulfides with an amorphous/crystalline (a/c) heterophase, in which aluminum, nitrogen, and carbon species were evenly coordinated in the amorphous phase. The metal sulfides a/c-Co(Al)S-1 and a/c-Co(Al)S-2, originating from the CAU-1 and CoAl-MOF on NF as self-sacrificial templates, were investigated as electrode materials, respectively, in which the a/c-Co(Al)S-1 showed a more excellent electrochemical performance. Through acid etching CAU-1 using Co(NO3)2 followed by sulfuration, the a/c-Co(Al)S-1 with a unique 3D network structure was constructed, whose unique architecture expanded the interfacial contact with the electrolyte and provided vast active sites, accelerating the charge transportation and ion diffusion. Notably, the a/c-Co(Al)S-1 displayed a high specific charge of 1791.8 C g-1 at 1 A g-1, satisfactory cycle stability, and good rate capability. The corresponding assembled a/c-Co(Al)S-1//AC device delivered a high energy density of 77.1 Wh kg-1 at 800 W kg-1 and good durability (87.4% capacitance retention over 10 000 cycles).

Boosting Photocatalytic Hydrogen Production by MOF-Derived Metal Oxide Heterojunctions with a 10.0 % Apparent Quantum Yield.

Photocatalytic hydrogen production offers an alternative pathway to establish a sustainable energy economy, utilizing the Earth's natural sunlight and water resources to address environmental concerns associated with fossil fuel combustion. While numerous photoactive materials exhibit high potential for generating hydrogen from water, the synergy achieved by combining two different materials with complementary properties in the form of heterojunctions can significantly enhance the rate of hydrogen production and quantum efficiency. Our study describes the design and generation of the metal-organic framework-derived (MOF) metal oxide heterojunction herein referred to as RTTA, composed of RuO2/N,S-TiO2. The RuO2/N,S-TiO2 is generated through the pyrolysis of MOFs, Ru-HKUST-1, and the amino-functionalized MIL-125-NH2 in the presence of thiourea. Among the various RTTA materials tested, RTTA-1, characterized by the lowest RuO2 content, exhibited the highest hydrogen evolution rate, producing 10,761 μmol ⋅ hr-1 ⋅ g-1 of hydrogen with an apparent quantum yield of 10.0 % in pure water containing glycerol. In addition to RTTA-1, we generated two other MOF-derived metal oxide heterojunctions, namely ZTTA-1 (ZnO/N,S-TiO2) and ITTA-1 (In2O3/N,S-TiO2). These heterojunctions were tested for their photocatalytic activity, leading to apparent quantum yields of 0.7 % and 0.3 %, respectively. The remarkable photocatalytic activity observed in RTTA-1 is thought to be attributed to the synergistic effects arising from the combination of metallic properties inherent in the metal oxides, complemented by the presence of suitable band alignment, porosity, and surface properties inherited from the parent MOFs. These properties enhance electron transfer and restrict hole movement. The photocatalytic efficiency of RTTA-1 was further demonstrated in actual water samples, producing hydrogen with a rate of 8,190 μmol ⋅ hr-1 ⋅ g-1 in tap water, and 6,390 μmol ⋅ hr-1 ⋅ g-1 in river water.

MOF-derived metal oxide (Cu, Ni, Zn) gas sensors with excellent selectivity towards H2S, CO and H2 gases

Metal-organic framework (MOF)-derived metal oxides blend the sensing properties of metal oxides with MOF porosity, enhancing gas sensing capabilities. In this study, M-MOFs (M = Cu, Ni and Zn) were synthesized and then calcined at different temperatures to obtain their corresponding metal oxides (CuO, NiO and ZnO). The synthesis method incorporated novel approaches to enhance sensor performance, such as optimizing calcination temperatures for improved selectivity. Structural and morphological analyses confirmed the high surface area and porosity of the metal oxide materials, facilitating efficient gas adsorption and promoting enhanced sensor response. Gas sensing studies revealed significantly enhanced performance of MOF-derived metal oxides over M-MOFs, strongly influenced by calcination temperature. Moreover, CuO, NiO and ZnO MOF-derived metal oxides showed improved selectivity towards H2S, CO and H2 gases, respectively. This study demonstrates that tuning MOF and calcination parameters can tailor sensor selectivity effectively.

In situ surface etching strategy for bimetallic MOFs-derived oxides and their catalytic properties

MOFs and their derivatives are excellent carriers with large specific surface area. Here, we propose a new strategy to engineer a supported-Pt core shell MOF-derived metal oxide catalyst. In this work, ZnCo-glycol microspheres were used as sacrificial templates, and the pre-prepared Pt nanoparticles were modified in MOFs during the in situ surface etching strategy. Compared to the ZnCo-2MI-330 and ZnCo–Pt-330, ZnCo–Pt-2MI-330 presents good catalytic activity (T10 = 110 °C,T90 = 123 °C) and excellent stability on CO oxidation reaction. By detailed characterization, ZnCo–Pt-2MI-330 remains the original pore structure of MOFs and provides a larger specific surface area, while the addition of Pt NPs changes the content of active species (the high ratio of Co3+ and active oxygen species) in the metal oxides. More importantly, the strategy effectively improves the noble metal catalysts are apt to lose their activities during the thermal catalytic caused by the serious working environment.

Synthesis and Characterization of MOF-Derived Structures: Recent Advances and Future Perspectives.

Due to their facile tunability, metal-organic frameworks (MOFs) are employed as precursors and templates to construct advanced functional materials with unique and desired chemical, physical, mechanical, and morphological properties. By tuning MOF precursor composition and manipulating conversion processes, various MOF-derived materials commonly known as MOF derivatives can be constructed. The possibility of controlled and predictable properties makes MOF derivatives a preferred choice for numerous advanced technological applications. The innovative synthetic designs besides the plethora of interdisciplinary characterization approaches applicable to MOF derivatives provide the opportunity to perform a myriad of experiments to explore the performance and offer key insight to develop the next generation of advanced materials. Though there are many published works of literature describing various synthesis and characterization techniques of MOF derivatives, it is still not clear how the synthesis mechanism works and what are the best techniques to characterize these materials to probe their properties accurately. In this review, the recent development in synthesis techniques and mechanisms for a variety of MOF derivates such as MOF-derived metal oxides, porous carbon, composites/hybrids, and sulfides is summarized. Furthermore, the details of characterization techniques and fundamental working principles are summarized to probe the structural, mechanical, physiochemical, electrochemical, and electronic properties of MOF and MOF derivatives. The future trends and some remaining challenges in the synthesis and characterization of MOF derivatives are also discussed.

Constructing Co and Zn atomic pairs in core-shell Co3S4/NC@ZnS/NC derived from MOF-on-MOF nanostructures for enhanced photocatalytic CO2 reduction to C2H4

Herein, a core-shell structured Co3S4/NC@ZnS/NC heterojunction has been constructed via elaborately synthesizing metal-organic framework (MOF)-on-MOF precursors (ZIF-67@ZIF-8) and following controlled carbonization-sulfidation processes. The developed Co3S4/NC@ZnS/NC achieves higher performances for CO2 photoreduction with water vapor towards CO (28.44 μmol g−1 h−1), CH4 (1.93 μmol g−1 h−1) and C2H4 (12.23 μmol g−1 h−1) in a continuous-flow condition under visible-light irradiation, which are significantly superior than those of Co3S4/NC and ZnS/NC. 13CO2 isotope tracer analysis verifies that CO, CH4 and C2H4 originate from the carbon source of CO2. Experiments and DFT calculations confirm that constructing an electron transport layer (ZnS/NC) in Co3S4/NC@ZnS/NC can contribute to a feasible channel for the enhanced separation and transfer of charge carriers. In heterojunction, non-bonding Co and Zn atomic pairs as adsorption sites synergistically participate in the CO2 activation through the unique electron transport channel and acquire the lower energy barriers of COOH* formation. Moreover, in situ DRIFTS reveals the key intermediates and possible conversion pathways to main products. This work presents an attractive strategy to construct dual MOFs-derived metal sulfide heterojunctions for high-performance CO2 conversion.

Nitrogen-doped carbon nanofiber loaded MOF-derived NiCo bimetallic nanoparticles accelerate the redox transformation of polysulfide for lithium- sulfur batteries

In the electrochemical study of lithium-sulfur (Li-S) batteries, the slow kinetics of the sulfur reduction reaction (SRR) leading to severe shuttle effect of polysulfides remains a major challenge. Catalysts with bimetallic nanoparticles have higher adsorption affinity for lithium polysulfides and hold great potential in improving reaction kinetics. In this study, a nitrogen-doped carbon nanofiber carrier was prepared using high-voltage electrospinning technology, and through in-situ growth and high-temperature pyrolysis process, the carrier material was uniformly loaded with active sites of NiCo bimetallic nanoparticles derived from Metal-organic framework (MOF), aiming to improve the kinetics of sulfur oxidation and reduction and reduce the severe shuttle effect of soluble polysulfides. At the same time, polymethyl methacrylate was added to adjust the pore structure of the carbon nanofibers to form an ideal independent sulfur cathode porous conductive carbon network for rapid ion transport to prevent Li2S deposition and alleviate the volume change during lithiation/delithiation process. Experimental results show that the synergistic catalytic effect of bimetallic nanoparticles can not only rapidly anchor lithium polysulfides throughout the entire reaction process of Li-S batteries, but also reduce the resistance during the reaction process, accelerating the conversion of lithium polysulfides to Li2S deposition. It demonstrates outstanding electrochemical performance, with a first-cycle discharge specific capacity as high as 1431.7 mAh g−1 at a 0.2 C rate, and a Coulombic efficiency of 96%. After 500 cycles, its capacity still maintains at 628.5 mAh g−1, with a decay rate of only 0.11% per cycle. This study provides a feasible insight into the synergistic catalysis of MOF-derived metal nanoparticles, which has important guiding significance and potential impact on the catalysis of Li-S batteries by bimetallic nanoparticles with an independent sulfur cathode structure, and is expected to accelerate the industrialization process of Li-S batteries.

Silicotungstic acid supported on Bi-based MOF-derived metal oxide for photodegradation of organic dyes

Abstract In this article, Bi-based metal–organic framework-supported silicotungstic acid (STA) was synthesized by a simple hydrothermal method and used as a precursor for the preparation of the Bi-based MOF-derived catalyst (STA@C-Bi-BDC). Using a combination of FTIR, XRD, SEM-EDS, N2 adsorption–desorption, TG, UV-Vis DRS, and XPS techniques, the successful immobilization of STA groups on Bi-MOF-derived C-Bi-BDC was assessed. Furthermore, the photocatalytic performance of the as-prepared catalysts was investigated in the degradation of the RhB dye process under visible light. Within 120 min of visible light exposure, the high degradation rate of RhB (92.7%) by STA@C-Bi-BDC system was achieved, which was a lot larger than the STA (39.4%), C-Bi-BDC (59.2%), and STA@Bi-BDC (74.0%) system, and cyclic experiments exhibit that the STA@C-Bi-BDC is a relatively stable photocatalyst. More importantly, the catalyst shows high applicability for the degradation of other dyes. This study reveals a comprehensive strategy for the design of efficient Bi-based MOF-derived photocatalyst for organic dye-based wastewater treatment.

Laser-Induced and MOF-Derived Metal Oxide/Carbon Composite for Synergistically Improved Ethanol Sensing at Room temperature

HighlightsMetal oxide and carbon hybrids (MOx/C) were micropatterned very rapidly and energy efficiently by direct laser writing.Metal-organic framework was the ideal precursor for fabricating homogeneous MOx/C hybrids due to regularly spaced metal ions and organic ligands.The fabricated sensor not only demonstrated broad-range gas sensing capability for ethanol gas (170-3,400 ppm) but also exhibited exceptional sensitivity, rapid response and recovery, selectivity, linearity, and thermal stability.

Photothermal-assisted S-scheme PDIs/C, N, S-CeO2 derived from MOF-808 (Ce) heterojunction for photocatalytic removal of antibiotics

In this research, an organic supermolecule self-assembly perylene diimides (PDIs) semiconductor was wrapped around the surface of three-dimensional metal oxides frame (C, N, S-CeO2) by oil bath heating method. The photocatalytic ability was determined by the degradation of organic pollutants under visible light. The photodegradation rate of tetracycline (TC) was nearly 80.1% within 30 min, and the apparent reaction rate constant (k) was 15.83 times higher than that of C, N, S-CeO2. Free radical capture experiments and electron spin resonance analysis showed that •O2-, •OH and 1O2 were the main active species. The structure of PDIs/C, N, S-CeO2 maintained stable after four cycles, meanwhile, anti-ion interference experiment illustrated that degradation efficiency was not affected by neutral ionic intensity. Further, the formation pathways of main degradation intermediates during the degradation process and the toxicity prediction of degradation intermediates were proposed. In addition, 10% PDIs/C, N, S-CeO2 could also efficiently degrade other organic pollutants (chlorotetracycline (CTC), ciprofloxacin (CIP), rhodamine B (RhB), methylene blue (MB)). The excellent photocatalytic activity of 10% PDIs/C, N, S-CeO2 was attributed to the matched energy band structure, establishment of multi-dimensional channels, more significant visible light assimilation performance and enhanced photothermal ability. This work provides a new perspective on the construction of n-n S-scheme heterojunction photocatalysts between self-assembled organic supramolecular materials and MOF-derived metal oxides.

A novel 1D MXene fibers-loaded metal-organic framework derived bimetallic sulfide for high-performance supercapacitors

Metal-organic frameworks (MOFs), when directly used as electrode materials, encounter issues due to their poor conductivity and low energy density, which restricts their practical application. In this work, the MXene-fibers has been obtained by treating flake Mxene with KOH solution firstly. Then, a novel composite of nanoscale one-dimensional (1D) Mxene-fibers loaded with MOFs-derived metal sulfides (Ni(Co)3S4@MXene-fibers) has been synthesized. The electrochemical analysis results show that the specific capacitance of Ni(Co)3S4@MXene-fibers reaches 829.4C g−1 at 1 A g−1. Moreover, the asymmetric device (Ni(Co)3S4@MXene-fibers//AC) has an energy density of 63.3 Wh kg−1 at a power densi ty of 850 W kg−1. This thanks for the 1D MXene-fibers. SEM and other characterization demonstrate that the 1D MXene-fibers can not only avoid the accumulation of Ni(Co)3S4, but also construct a stable structure with fast charge transfer ability. Besides, it is more conducive to the redox reaction of active substances loaded on its surface, which improves the electrochemical performance.

Catalytic deoxygenation of stearic acid into olefins over Pt catalysts supported on MOF-derived metal oxides

The deoxygenation of stearic acid over Pt supported on different metal oxides can affect the product selectivity.

Phosphorization Engineering on a MOF-Derived Metal Phosphide Heterostructure (Cu/Cu3P@NC) as an Electrode for Enhanced Supercapacitor Performance.

A highly conductive and rationally constructed metal-organic framework (MOF)-derived metal phosphide with a carbonaceous nanostructure is a meticulous architecture toward the development of electrode materials for energy storage devices. Herein, we report a facile strategy to design and construct a new three-dimensional (3D) Cu-MOF via a solvent diffusion method at ambient temperature, which was authenticated by a single-crystal X-ray diffraction study, revealing a novel topology of (2,4,7)-connected three-nodal net named smm4. Nevertheless, the poor conductivity of pristine MOFs is a major bottleneck hindering their capacitance. To overcome this, we demonstrated an MOF-derived Cu3P/Cu@NC heterostructure via low-temperature phosphorization of Cu-MOF. The electronic and ionic diffusion kinetics in Cu3P/Cu@NC were improved due to the synergistic effects of the heterostructure. The as-prepared Cu3P/Cu@NC heterostructure electrode delivers a specific capacity of 540 C g-1 at 1 A g-1 with outstanding rate performance (190 C g-1 at 20 A g-1) and cycle stability (91% capacity retention after 10,000 cycles). Moreover, the assembled asymmetric solid-state supercapacitor (ASC) achieved a high energy density/power density of 45.5 Wh kg-1/7.98 kW kg-1 with a wide operating voltage (1.6 V). Long-term stable capacity retention (87.2%) was accomplished after 5000 cycles. These robust electrochemical performances suggest that the Cu3P/Cu@NC heterostructure is a suitable electrode material for supercapacitor applications.

High response and selectivity of bimetallic MOFs-derived metal oxides Co3O4/In2O3 nanoparticles to TEA

Metal-organic Frameworks (MOFs) are promising precursors and templates for the construction of porous micro/nanostructures. In this work, we prepared a bimetallic MOFs-derived metal oxide Co3O4/In2O3 nanoparticles (NPs) gas sensor by hydrothermal method for the detection of TEA. The composition, microstructure and gas sensitivity of Co3O4/In2O3 NPs were investigated. The results show that Co3O4/In2O3 NPs have excellent response and selectivity to TEA. At 225 °C, the response of Co3O4/In2O3 NPs to 20 ppm TEA reaches 365.3, which is 30.2 times the response of the pristine In2O3. The reason for the improvement of the gas sensing performance of Co3O4/In2O3 NPs and the gas sensing mechanism were discussed in detail.

Ligand-engineered Ru-doped cobalt oxides derived from metal-organic frameworks for large-current-density water splitting

The influence of the preorganized structure and chemical composition of metal-organic frameworks (MOFs) on the morphology, surface properties, and catalytic activity of the MOFs-derived metal oxides is yet to be revealed. In this work, two types of Co-MOFs with different coordination configurations are synthesized for the preparation of the structure-engineered ruthenium (Ru)-doped cobalt oxides. The effect of the preorganized coordination structure of the MOFs on the morphology and surface properties is investigated. Interestingly, the oxalate-based MOFs derived Ru-doped cobalt oxide (OX-Co3O4-Ru) exhibits much better surface wettability and more oxygen vacancies than the zeolitic imidazolate framework-67 derived Ru-doped cobalt oxide. As expected, the OX-Co3O4-Ru owns excellent catalytic properties towards both hydrogen evolution reaction and oxygen evolution reaction with an overpotential of 49 and 286 mV, respectively at a current density of 100 mA cm−2 in 1.0 M KOH. Importantly, the bifunctional OX-Co3O4-Ru catalyst offers an extremely high current density of 500 mA cm−2 at a cell voltage of 1.71 V for overall water splitting and as well demonstrates robust working stability.

MOF/bacterial cellulose derived octahedral MnO/carbon nanofiber network: A hybrid for peroxymonosulfate activation toward degradation of tetracycline

Metal-organic frameworks (MOFs) derived materials have distinctive structures and conspicuous catalytic performance, making them extensively employed as catalysts in several fields. Herein, MnO/carbon nanofiber has been successfully generated by pyrolyzing Mn-MOF/bacterial cellulose (BC) composite, in which BC serves as a structural support for the growth of Mn-MOF. The characterizations of field-emission scanning electron microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy demonstrate the effective synthesis of MOFs-derived MnO that maintains its original octahedral structure. MnO/carbon nanofiber is applied as a catalyst to activate peroxymonosulfate (PMS) for the degradation of tetracycline (TC), exhibiting remarkable catalytic activity with 90.59% TC decomposition generated after 30 min. Meanwhile, the removal efficiency for TC remains 83.38% after five cycles. Besides, the quenching experiments confirm not only synergistic effect of radical and non-radical species, but also the vital role of singlet oxygen (1O2) in MnO/CBC-PMS system. This work constructs a new pathway in the preparation of high-performance MOFs-derived metal oxides/carbon materials, which have the potential to enhance the activity in activating peroxymonosulfate for effluent disposal.

Localized ultrafine Cu clusters within MOF-derived metal oxides for collective photochemical and photothermal H2 generation

The ability to prepare ultrafine metal cluster (UMC) in supported catalysts, which exhibit extraordinary physical and chemical properties offers exciting opportunities to tailoring catalytic performance. However, the fabrication of singly-dispersed metal cluster catalysts that are both catalytic stable and active remains challenging. In this work, ultrafine Cu clusters has been spatially immobilized within the MOF derived photocatalyst matrix to realize a unitary photocatalyst with high density and stable active sites for charge separation and photothermal co-functions. Furthermore, the embedded Cu is capable of overcoming challenges related to porous structure collapse, disparate material interfaces and incompatibility between light absorption and charge transfer processes. Resultantly, the photocatalyst (m-TiO2/Cu) exhibits a high and stable H2 generation rate of 17.8 mmolg−1h−1 that is ∼69 times higher compared to the control. In essence, this study presents an efficient approach to immobilize ultrafine metal active sites for the development of high-performance heterogeneous catalysts for energy applications.

High sensitivity and surface mechanism of MOFs-derived metal oxide Co3O4-SnO2 hollow spheres to ethanol

Metal-organic Frameworks (MOFs) have been widely studied due to their high porosity and large surface area. In this paper, Co3O4-modified SnO2 hollow spheres with excellent ethanol gas sensitivity were prepared by using ZIF-67 as template by two-step hydrothermal pyrolysis at 300 °C. The elemental composition, morphology, structure and gas sensitivity properties of the materials were characterized by XRD, SEM and gas-sensitive analysis system. The experiment shows that the ZIF-67-derived Co3O4-SnO2 composite has a response value of 33.9 to 100 ppm ethanol gas at the optimum operating temperature of 225 °C, which is significantly higher than that of pure SnO2. According to the characteristics of gas sensitivity and morphology, the enhancement of gas sensitivity is due to the increase of oxygen vacancies, which promotes oxygen adsorption and surface chemical reaction.