Search Results (8)

To achieve high electrooxidation efficiency for phenol, this study explored the fabrication of Mn-MIL-100 catalysts at various calcination temperatures, loaded onto a carbon paper (CP) anode. The materials were characterized using scanning electron micros-copy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and X-ray diffraction. Their electrocatalytic activities under various calcination temperatures were evaluated through cyclic voltammetry (CV) tests, while the effect of pH in the Mn-MOF modified CP electrodes on phenol degradation performance was investigated using the potentiostatic discharge method. Mn-MOF@CP calcined at 400 °C and 500 °C (denoted as Mn400@CP and Mn500@CP, respectively) exhibited significantly enhanced cyclic voltammetry current responses in phenol solution, attributed to an increase in oxygen vacancy concentration. A phenol degradation efficiency of 96.00 ± 1.53% was achieved by Mn400@CP within 16 h, while it was only 60.12 ± 2.03% for Mn500@CP and 8.01 ± 2.00% for the blank CP at pH 4. Additionally, Mn400@CP consistently demonstrated superior phenol degradation efficiency over Mn500@CP across various pH values. The outstanding electrocatalytic activity of Mn400@CP for phenol oxidation could be attributed to its lower charge transfer resistance. A radical-mediated oxidation pathway was proposed for the Mn400@CP electrocatalytic system, elucidating its phenol degradation mechanism. These findings highlighted the potential of Mn-MOF-derived carbon-based materials for the degradation of organic contaminants. Full article

Efforts have been made to improve the therapeutic efficiency of tumor treatments, and metal-organic frameworks (MOFs) have shown excellent potential in tumor therapy. Monotherapy for the treatment of tumors has limited effects due to the limitation of response conditions and inevitable multidrug resistance, which seriously affect the clinical therapeutic effect. In this study, we chose to construct a multiple cascade synergistic tumor drug delivery system MIL−101(Fe)−DOX−TCPP−MnO₂@PDA−Ag (MDTM@P−Ag) using MOFs as drug carriers. Under near-infrared (NIR) laser irradiation, 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) and Ag NPs loaded on MDTM@P−Ag can be activated to generate cytotoxic reactive oxygen species (ROS) and achieve photothermal conversion, thus effectively inducing the apoptosis of tumor cells and achieving a combined photodynamic/photothermal therapy. Once released at the tumor site, manganese dioxide (MnO₂) can catalyze the decomposition of hydrogen peroxide (H₂O₂) in the acidic microenvironment of the tumor to generate oxygen (O₂) and alleviate the hypoxic environment of the tumor. Fe³⁺/Mn²⁺ will mediate a Fenton/Fenton-like reaction to generate cytotoxic hydroxyl radicals (·OH), while depleting the high concentration of glutathione (GSH) in the tumor, thus enhancing the chemodynamic therapeutic effect. The successful preparation of the tumor drug delivery system and its good synergistic chemodynamic/photodynamic/photothermal therapeutic effect in tumor treatment can be demonstrated by the experimental results of material characterization, performance testing and in vitro experiments. Full article

As a commonly used food additive, sulfite (SO₃²⁻) is popular with food manufacturers due to the functions of bleaching, sterilizing, and oxidation resistance. However, excess sulfites can pose a threat to human health. Therefore, it is particularly important to achieve rapid and sensitive detection of SO₃²⁻. Herein, a colorimetric sensor was invented for visual, meticulous, and rapid detection of SO₃²⁻ based on MIL-53(Fe/Mn). Bimetallic nanozyme MIL-53(Fe/Mn) was prepared by a one-pot hydrothermal reaction. The prepared MIL-53(Fe/Mn) can effectively catalyze the oxidation of colorless TMB to a blue oxidation product (oxTMB). The introduction of SO₃²⁻ causes significant discoloration of the reaction system, gradually transitioning from a visible blue color to colorless. Hence, a sensitive colorimetric sensor for SO₃²⁻ detection was developed based on the decolorization degree of the detection system. Further, the discoloration was ascribed to the inactivation of nanozyme and the strong reducing ability of SO₃²⁻. Under the optimal experimental conditions, there was a good linear relationship between the absorbance at 652 nm and SO₃²⁻ concentration in the linear range of 0.5–6 μg mL⁻¹ with a limit of detection (LOD) of 0.05 μg mL⁻¹. The developed method was successfully applied to the detection of actual samples of white wine with good accuracy and recovery. Compared to traditional methods, this colorimetric sensor produces similar detection results but significantly reduces the detection time. Compared to traditional methods, this colorimetric sensor can not only reduce the detection costs effectively but also help the food industry maintain quality standards. Strong anti-interference capability, simple operation, and low detection limits ensure the excellent performance of the colorimetric sensor in detecting SO₃²⁻ in white wine. The combination of a smartphone and a colorimetric analysis application has also greatly facilitated the semi-quantitative, visual on-site detection of SO₃²⁻, which has opened up an application prospect of an MIL-53(Fe/Mn)-based detection platform. Our work has indicated a new direction for the detection of SO₃²⁻ and provided important assurance for food safety. Full article

In this study, a facile strategy of regulated self-assembly synthesis of Mn-MIL-100, using sodium acetate (CH₃COONa) as a mono-dentate ligand capping agent (CA), was proposed. The as-prepared product is denoted Mn-MIL-100-CA. The coordination modulation of CH₃COONa, led by its interference in the connectivity and symmetry of the metal centers and organic nodes, plays a vital role in the synthesis process. The crystallinity, morphology, topology, and properties of such MOF products were improved, since the self-assembly process of Mn-MIL-100-CA was promoted and regulated effectively. The materials were systematically characterized via XRD, SEM, N₂ isotherms, XPS, and TGA in terms of crystallization behavior, morphology, topology, chemical composition, and thermal and water stability. The ability of Mn-MIL-100 and Mn-MIL-100-CA to remove methylene blue (MB) from an aqueous solution was investigated using a UV–vis spectrophotometer. The results indicate that with the addition of a molar ratio of 50% CH₃COONa, Mn-MIL-100-CA particles developed a regularly symmetrical morphology, i.e., ‘spherical pyramid-like structure’ crystals with a dimension of 2~5 μm. Their specific surface area and pore volume increased by 59.2% and 56.7%, respectively. The increased proportion of Mn³⁺ implies reduced crystal defects and improved crystal structural order and integrity, and therefore an enhanced water stability. Mn-MIL-100-CA exhibited excellent adsorption performance towards MB from aqueous solution. The equilibrium adsorption value was as high as 1079.9 mg/g, which is 44.7% higher than that of Mn-MIL-100 without the addition of CA. The good adsorption capacity and excellent water stability mean that Mn-MIL-100-CA has great potential for the practical removal of MB dye pollutants from water. Full article

Lithium–sulfur batteries (LSBs) show excellent performance in terms of specific capacity and energy density. However, the cyclic stability of LSBs is compromised due to the “shuttle effect”, which hinders the practical applications of LSBs. Herein, a metal–organic framework (MOF) based on Cr ions as the main body composition, commonly known as MIL-101(Cr), was utilized to minimize the shuttle effect and improve the cyclic performance of LSBs. To obtain MOFs with a certain adsorption capacity for lithium polysulfide and a certain catalytic capacity, we propose an effective strategy of incorporating sulfur-loving metal ions (Mn) into the skeleton to enhance the reaction kinetics at the electrode. Based on the oxidation doping method, Mn²⁺ was uniformly dispersed in MIL-101(Cr) to produce bimetallic Cr₂O₃/MnO_x as a novel sulfur-carrying cathode material. Then, a sulfur injection process was carried out by melt diffusion to obtain the sulfur-containing Cr₂O₃/MnO_x-S electrode. Moreover, an LSB assembled with Cr₂O₃/MnO_x-S showed improved first-cycle discharge (1285 mAh·g⁻¹ at 0.1 C) and cyclic performance (721 mAh·g⁻¹ at 0.1 C after 100 cycles), and the overall performance was much better than that of monometallic MIL-101(Cr) as a sulfur carrier. These results revealed that the physical immobilization method of MIL-101(Cr) positively affected the adsorption of polysulfides, while the bimetallic composite Cr₂O₃/MnO_x formed by the doping of sulfur-loving Mn²⁺ into the porous MOF produced a good catalytic effect during LSB charging. This research provides a novel approach for preparing efficient sulfur-containing materials for LSBs. Full article

Light olefins are important raw materials in the petrochemical industry for the production of many chemical products. In the past few years, remarkable progress has been made in the synthesis of light olefins (C2–C4) from methanol or syngas. The separation of light olefins by porous materials is, therefore, an intriguing research topic. In this work, single-component ethylene (C₂H₄) and propylene (C₃H₆) gas adsorption and binary C₃H₆/C₂H₄ (1:9) gas breakthrough experiments have been performed for three highly porous isostructural metal–organic frameworks (MOFs) denoted as Fe₂M-L (M = Mn²⁺, Co²⁺, or Ni²⁺), three representative MOFs, namely ZIF-8 (also known as MAF-4), MIL-101(Cr), and HKUST-1, as well as an activated carbon (activated coconut charcoal, SUPELCO^©). Single-component gas adsorption studies reveal that Fe₂M-L, HKUST-1, and activated carbon show much higher C₃H₆ adsorption capacities than MIL-101(Cr) and ZIF-8, HKUST-1 and activated carbon have relatively high C₃H₆/C₂H₄ adsorption selectivity, and the C₂H₄ and C₃H₆ adsorption heats of Fe₂Mn-L, MIL-101(Cr), and ZIF-8 are relatively low. Binary gas breakthrough experiments indicate all the adsorbents selectively adsorb C₃H₆ from C₃H₆/C₂H₄ mixture to produce purified C₂H₄, and 842, 515, 504, 271, and 181 cm³ g⁻¹ C₂H₄ could be obtained for each breakthrough tests for HKUST-1, activated carbon, Fe₂Mn-L, MIL-101(Cr), and ZIF-8, respectively. It is worth noting that C₃H₆ and C₂H₄ desorption dynamics of Fe₂Mn-L are clearly faster than that of HKUST-1 or activated carbon, suggesting that Fe₂M-L are promising adsorbents for C₃H₆/C₂H₄ separation with low energy penalty in regeneration. Full article

As ordered porous materials, metal–organic frameworks (MOFs) have attracted tremendous attention in the field of energy conversion and storage due to their high specific surface area, permanent porosity, and tunable pore sizes. Here, MOF-derived MnO/C nanocomposites with regular octahedral shape were synthesized using a Mn-based analogue of the MIL-100 framework (Mn-MIL-100, MIL: Matérial Institut Lavoisier) as the precursor. Using aberration-corrected environmental transmission electron microscopy (ETEM), MnO nanocages with a diameter of approximately 20 nm were recognized in the MnO/C nanocomposites fabricated, dispersed in a microporous carbon matrix homogeneously. The nanocages are composed of MnO nanoparticles with a diameter of approximately 2 nm and with a single crystal structure. The specific surface area of the as-prepared MnO/C octahedra decreases to 256 m² g⁻¹ from 507 m² g⁻¹ of the Mn-MIL-100 precursor, whereas the total pore volume increases to 0.245 cm³ g⁻¹, which is approximately 29% higher than that of the precursor (0.190 cm³ g⁻¹). Additionally, when utilized as an electrode for supercapacitors, the MOF-derived MnO/C nanocomposite demonstrates a towering specific capacitance of 421 F g⁻¹ at 0.5 A g⁻¹ and good cycle stability (94%) after 5000 cycles. Our work reveals that the MnO nanoparticles in MOF-derived MnO/C nanocomposites exhibit nanocage structure characteristics, which might be inherited from the Mn-MIL-100 precursor with analogous supertetrahedron units. Full article

Samples of the bimetallic-based NH₂-MIL-125(Ti) at a ratio of Mⁿ⁺/Ti⁴⁺ is 0.15 (Mⁿ⁺: Ni²⁺, Co²⁺ and Fe³⁺) were first synthesized using the solvothermal method. Their fundamental properties were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectra, scanning electron microscopy (SEM), N₂ adsorption–desorption measurements, and UV–Vis diffuse reflectance spectroscopy (UV-Vis DRS). The as-acquired materials were used as high-efficiency heterogeneous photocatalysts to remove Rhodamine B (RhB) dye under visible light. The results verified that 82.4% of the RhB (3 × 10⁻⁵ M) was degraded within 120 min by 15% Fe/Ti−MOFs. Furthermore, in the purpose of degrading Rhodamine B (RhB), the rate constant for the 15% Fe/Ti-MOFs was found to be 2.6 times as fast as that of NH₂-MIL-125(Ti). Moreover, the 15% Fe/Ti-MOFs photocatalysts remained stable after three consecutive cycles. The trapping test demonstrated that the major active species in the degradation of the RhB process were hydroxyl radicals (HO^∙) and holes (h⁺). Full article