Conversion Of Metal-organic Frameworks Research Articles

Direct Conversion of Metal Organic Frameworks into Porous Rugby Phosphides by Plasma for Oxygen Evolution.

Electrolytic seawater is a green, sustainable, and promising approach for hydrogen production. Benefiting from the cost-effectiveness, crystal structures, and tailorable modification, transition metal phosphides become a highly attractive catalyst for the electrolysis of water. Considering the sufficient exposure and intrinsic catalytic activity of metal sites, here, carbon layer-coated NiFeP nanocrystals with a porous rugby structure are synthesized by Ar-H2 plasma. Activated PH radical in plasma is the key point to achieve phosphatization at a low temperature. The obtained porous rugby NiFeP catalyst exhibits excellent catalytic activity under alkaline conditions (300 mV in freshwater and 370 mV in seawater, 1000 mA cm-2), good corrosion resistance, and superior operational stability (>100 h). Theoretical calculations prove that Fe introduction and subsequent phosphorization weaken the adsorption of *O and *OH, thus improving the oxygen evolution reaction performance. Plasma phosphorization offers exciting opportunities for the in situ modification of other types of framework materials.

α-Fe2O3 derived from metal-organic frameworks as high performance sensing materials for acetone detection

High-performance gas sensors are critical for monitoring the environment, detecting health problems and ensuring safety. Metal-organic frameworks (MOFs) are considered promising gas-sensitive materials due to their elevated porosity, large specific surface area, and various morphologies. The conversion of MOFs into metal oxides can be achieved by oxidation and roasting processes, where the structure and surface chemical composition are significantly affected by the temperature at which the roasting is performed. The structures of α-Fe2O3 have been controlled by optimizing the heat treatment temperatures (350 °C, 400 °C, 450 °C and 500 °C) using MIL-100(Fe) as template which was synthesized using a hydrothermal method with reduced iron powder and 1,3,5-BTC as precursors. The gas sensitivity tests revealed that the α-Fe2O3 material obtained through annealing at 400 °C exhibited excellent sensitivity to acetone，which can be attributed to the combination of its porous structure and oxygen vacancy defects. Gas-sensitive materials, synthesized using MOFs as a template with meticulous tuning of the calcination temperature, exhibit exceptional properties. These materials hold great potential for advancing sensor materials in the field of gas sensor technology.

Simultaneous Catechol and Hydroquinone Detection with Laser Fabricated MOF-Derived Cu-CuO@C Composite Electrochemical Sensor.

The conversion of metal-organic frameworks (MOFs) into advanced functional materials offers a promising route for producing unique nanomaterials. MOF-derived systems have the potential to overcome the drawbacks of MOFs, such as low electrical conductivity and poor structural stability, which have hindered their real-world applications in certain cases. In this study, laser scribing was used for pyrolysis of a Cu-based MOF ([Cu4{1,4-C6H4(COO)2}3(4,4'-bipy)2]n) to synthesize a Cu-CuO@C composite on the surface of a screen-printed electrode (SPE). Scanning electron microscopy, X-ray diffractometry, and Energy-dispersive X-ray spectroscopy were used for the investigation of the morphology and composition of the fabricated electrodes. The electrochemical properties of Cu-CuO@C/SPE were studied by cyclic voltammetry and differential pulse voltammetry. The proposed flexible electrochemical Cu-CuO@C/SPE sensor for the simultaneous detection of hydroquinone and catechol exhibited good sensitivity, broad linear range (1-500 μM), and low limits of detection (0.39 μM for HQ and 0.056 μM for CT).

Nanoscale designing of metal organic framework moieties as efficient tools for environmental decontamination.

Environmental pollutants, being a major and detrimental component of the ecological imbalance, need to be controlled. Serious health issues can get intensified due to contaminants present in the air, water, and soil. Accurate and rapid monitoring of environmental pollutants is imperative for the detoxification of the environment and hence living beings. Metal-organic frameworks (MOFs) are a class of porous and highly diverse adsorbent materials with tunable surface area and diverse functionality. Similarly, the conversion of MOFs into nanoscale regime leads to the formation of nanometal-organic frameworks (NMOFs) with increased selectivity, sensitivity, detection ability, and portability. The present review majorly focuses on a variety of synthetic methods including the ex situ and in situ synthesis of MOF nanocomposites and direct synthesis of NMOFs. Furthermore, a variety of applications such as nanoabsorbent, nanocatalysts, and nanosensors for different dyes, antibiotics, toxic ions, gases, pesticides, etc., are described along with illustrations. An initiative is depicted hereby using nanostructures of MOFs to decontaminate hazardous environmental toxicants.

Conductive substrates-based component tailoring via thermal conversion of metal organic framework for enhanced microwave absorption performances

Component tailoring, especially for the conductive substrates-based composites, acts as a significant role in optimizing the electromagnetic (EM) parameters and improving the EM response capability. Here, Fe-based metal oxides modified rGO microwave absorbers with component evolution were fabricated through hydrothermal treatment and subsequent pyrolysis process. The synergistic effects of the dielectric loss (multi-relaxations) and the magnetic loss (resonance and eddy current) are found to be effective in promoting the microwave absorption property of Fex-1Ox/C/rGO absorbers. As the thermal treatment temperature reaches 500 °C, the as-prepared composite sample shows ideal microwave absorption performance, where the reflection loss value is −25.94 dB, and the effective bandwidth reaches 5.84 GHz at 1.9 mm. In addition, CST simulation was employed to analyze the microwave absorption capability in the actual far field. When the scattering angle is 0° and 20°, the radar cross section (RCS) reduction of S-500/PEC layers is 8.11 dB m2 and 8.80 dB m2, respectively. This study exhibits the importance of component tailoring in enhancing the performances of substrates-based microwave absorption materials.

Unlocking active metal site of Ti-MOF for boosted heterogeneous catalysis via a facile coordinative reconstruction

Constructing sophisticated hollow structure and exposing more metal sites in metal-organic frameworks (MOFs) can not only enhance their catalytic performance but also endow them with new functions. Herein, we present a facile coordinative reconstruction strategy to transform Ti-MOF polyhedron into nanosheet-assembled hollow structure with a large amount of exposed metal sites. Importantly, the reconstruction process relies on the esterification reaction between the organic solvent, i.e. ethanol and the carboxylic acid ligand, allowing the conversion of MOF without the addition of any other modulators and/or surfactants. Moreover, the surface and internal structure of the reconstructed MOF can be well tuned via altering the conversion time. Impressively, the reconstructed MOF exhibits ∼5.1-fold rate constant compared to the pristine one in an important desulfurization reaction for clean fuels production, i.e. the oxidation of dibenzothiophene.

Pyrolysis conversion of metal organic frameworks to form uniform codoped C/N-Titania photocatalyst for H2 production through simulated solar light

In this contribution, C/N-TiO2 photocatalyst has been synthesized employing the combustion approach of NH2-MIL-125(Ti) at 400 °C in air for H2 production through simulated solar light compared with either NH2-MIL-125(Ti) or commercial P-25. TEM images show well defined shape TiO2 nanocrystalline with 10 nm particles size. The obtained C/N-TiO2 photocatalyst exhibited large surface area 1066 m2 g−1 with high pore volume ∼0.537 cm3 g−1 and pores diameter ∼1.3 nm. The yield of H2 evolution over C-N/TiO2 photocatalyst (339 H2 mmol g−1) exhibited significantly compared with NH2-MIL-125(Ti) (5.7 H2 mmol g−1) and P-25 TiO2 (144.8 H2 mmol g−1) photocatalyst. The yield of H2 evolution over C/N-doped TiO2 was boosted by 60 and 2.35 times after 6 h over NH2-MIL-125(Ti) and P-25 TiO2 photocatalyst. The H2 evolution rate of C/N-TiO2 photocatalyst reached 33.3 mmol g-1 h-1 and it is greater 2.17 and 27.5 times than P-25 TiO2 (15.3 mmol g-1 h−1) and NH2-MIL-125(Ti) (1.212 mmol g-1 h−1). The enhancement of photocatalytic efficiency over C/N-TiO2 photocatalyst was referred to its great mesoporosity, hierarchical structure and large surface area. The recycled C/N-TiO2 photocatalyst showed significant durability through five consecutive runs for 30 h illumination. The C/N-TiO2, synthesized from pyrolysis of NH2-MIL-125(Ti), is proposed as an outstanding material for H2 evolution and potential photocatalysis application under simulated solar Light.

Construction of nickel cobalt sulfide nanosheet arrays on carbon cloth for performance-enhanced supercapacitor

Materials featured with self-supported three-dimensional network, hierarchical pores and rich electrochemical active sites are considered as promising electrodes for pseudocapacitors. Herein, a novel strategy for the growth of nickel-cobalt bisulfide (NiCoS) nanosheets arrays on carbon cloth (CC) as supercapacitor electrodes is reported, involving deposition of two-dimensional metal-organic framework (MOF) precursors on the CC skeletons, conversion of MOF into nickel-cobalt layered double-hydroxide by ion exchange process and formation of NiCoS by a sulfidation treatment. The NiCoS nanosheets with rough surface and porous structures are uniformly anchored on the CC skeletons. The unique architecture endows the composite (NiCoS/CC) with abundant accessible active sites. Besides, robust electrical/mechanical joint between the nanosheets and the substrates is attained, leading to the improved electrochemical performance. Moreover, an asymmetric supercapacitor device is constructed by using NiCoS/CC and activated carbon as a positive electrode and a negative electrode, respectively. The optimized device exhibits a high specific capacitance, large energy density and long cycle life. The NiCoS/CC electrode with intriguing electrochemical properties and mechanical flexibility holds great prospect for next-generation wearable devices.