Magnetically separable Fe3O4 NPs/MIL-53(Al) nanocomposite catalyst for intrinsic OPD oxidation and colorimetric hydrogen peroxide detection

Investigation on the Drug Release Efficacy of the Ibuprofen-Loaded ZIF-8/Fe3O4 NPs Nanocarrier

In this work, a one-pot multicomponent synthesis of the ibuprofen-loaded Fe3O4 nanoparticles-supported zeolitic imidazolate framework-8 (Ibu-ZIF-8/Fe3O4 NPs) nanohybrid was carried out. The ZIF-8/Fe3O4 NPs nanohybrid was used as a drug carrier for the in vitro release of ibuprofen in a PBS solution. The structure and morphology of the synthesized materials were investigated by powder X-ray diffraction (PXRD) analysis, transmission electron microscopy (TEM) analysis, UV-visible absorption studies, FTIR spectroscopy, and thermogravimetric analysis (TGA). The ibuprofen release kinetics was studied by UV-visible spectroscopy. The mechanism of drug delivery was thoroughly investigated and the Higuchi model was found as the best-fitted model for the ibuprofen release study. The 20 wt % Fe3O4 NPs-supported ZIF-8 nanohybrid exhibited more than 95% ibuprofen release efficiency in phosphate buffer saline of pH 7.4 within 2 h. The separation ability of the nanohybrid was very good, and it was easily separated by a simple commercial magnet. In order to investigate the cell viability, the cytotoxicity of ZIF-8, Fe3O4 NPs, and ZIF-8/20 wt % Fe3O4 NPs was investigated using MTT assays against Leishmania donovani promastigotes. The ZIF-8/20 wt % Fe3O4 NPs nanohybrid carrier exhibited a cell growth inhibition effect with a high correlation coefficient and low probability (p) values. The high release of drug molecules may be due to the more open site of the ZIF-8/Fe3O4 NPs nanohybrid. The drug release profile suggests that the nanohybrid can be potentially used as a drug carrier for targeted drug delivery systems.

Controlled Synthesis of Preferential Facet-Exposed Fe-MOFs for Ultrasensitive Detection of Peroxides

Exposing different facets on metal-organic frameworks (MOFs) is highly desirable to enhance the performance for various applications, however, exploiting a concise and effective approach to achieve facet-controlled synthesis of MOFs remains challenging. Here, by modulating the ratio of metal precursors to ligands, the facet-engineered iron-based MOFs (Fe-MOFs) exhibits enhanced catalytic activity for Fenton reaction are explored, and the mechanism of facet-dependent performance is revealed in detail. Fully exposed (101) and (100) facets on spindle-shaped Fe-MOFs enable rapid oxidation of colorless o-phenylenediamine (OPD) to colored products, thereby establishing a dual-mode platform for the detection of hydrogen peroxide (H2O2) and triacetone triperoxide (TATP). Thus, a detection limit as low as 2.06 nm is achieved, and robust selectivity against a wide range of common substances (>16 types) is obtained, which is further improved by incorporating a deep learning architecture with an SE-VGG16 network model, enabling precise differentiation of oxidizing agents from captured images. The present strategy is expected will shine light on both the rational synthesis of nanomaterials with modulated morphologies and the exploitation of high-performance trace chemical sensors.

In situ synthesis of oxygen-doped carbon quantum dots embedded in MIL-53(Fe) for efficient degradation of oxytetracycline

Introducing carbon quantum dots (CQDs) into photocatalysts is believed to boost the charge transfer rate and reduce charge complexation. Doping heteroatoms such as N, S, or P enable CQDs to have an uplifting electron transfer capability. However, the application of oxygen-doped CQDs to improve the performance of photocatalysts has rarely been reported. Herein, a type of carbon-oxygen quantum dots (COQDs) was in situ embedded into MIL-53(Fe) to aid peroxydisulfate (PDS)-activated degradation of oxytetracycline (OTC) under visible light irradiation. The successful embedding of COQDs was confirmed by XRD, FT-IR, XPS, SEM, and TEM techniques. Photoelectrochemical testing confirmed its better performance. The prepared COQDs1/MIL-53(Fe) showed 88.2% decomposition efficiency of OTC in 60 min, which was 1.45 times higher than that of pure MIL-53(Fe). In addition, the performance of the material was tested at different pH, OTC concentrations, catalyst dosing, and PDS dosing. It was also subjected to cyclic testing to check stability. Moreover, free radical trapping experiments and electron paramagnetic resonance were conducted to explore the possible OTC deterioration mechanism. Our work provides a new idea for the development of MOFs for water treatment and remediation.

Sulfonic acid-functionalized chitosan-metal-organic framework composite for efficient and rapid conversion of fructose to 5-hydroxymethylfurfural

In pursuit of designing a bio-based catalyst for the dehydration of biomass (i.e., fructose) to 5-hydroxymethylfurfural, a novel catalytic composite was prepared by in-situ formation of an Al-based metal-organic framework in the presence of chitosan. To enhance the acidity of the as-prepared catalyst, it was sulfonated with chlorosulfonic acid. Various characterization techniques, including XRD, XPS, FTIR, SEM/EDX, TGA, and elemental mapping analysis were applied to validate the formation of the acidic composite. Fructose dehydration conditions were also optimized using Response Surface Method (RSM) and it was found that reaction in the presence of catalyst (23 wt%) in DMSO, at 110 °C for 40 min led to the formation of HMF in 97.1%. Noteworthy, the catalyst was recyclable and stable up to five runs with a minor reduction in its activity.

Removal of oxytetracycline from water by S-doped MIL-53(Fe): Synergistic effect of surface adsorption and persulfate activation

In this study, a novel catalyst based on MIL-53(Fe) was synthesized and modified through sublimed sulfur (S-MIL-53(Fe)) to induce a synergistic effect of surface adsorption and persulfate activation. The S-doped modification not only increased the surface area but also accelerated the electron transfer process of the iron cycle. The performance of the newly synthesized S-MIL-53(Fe) adsorptive catalyst was evaluated by chemical adsorption and peroxydisulfate (PDS) activated removal of an emerging pollutants, oxytetracycline (OTC). The S-MIL-53(Fe) adsorptive catalyst was able to adsorb 61.7% of OTC after 120 min, and the removal efficiency reached 84.8% within 5 min after PDS dosing. The boosting effect of sulfur on the system was confirmed by characterization analysis and experimental testing. Even after 7 cycles, the removal efficiency of S-MIL-53(Fe) (69.0%) for OTC remained superior to that of pure MIL-53(Fe) (25.1%). Additionally, the adsorption kinetics and adsorption isotherm model of the material were investigated. The possible OTC degrading process was proposed based on radical quenching and electron paramagnetic resonance (EPR). This study provides a feasible way to fabricate an S-doped MIL-53(Fe) adsorptive catalyst for the remediation of antibiotics-containing wastewater.

Iodide-Mediated Etching of Gold Nanostar for the Multicolor Visual Detection of Hydrogen Peroxide

A multicolor visual method for the detection of hydrogen peroxide (H₂O₂) was reported based on the iodide-mediated surface etching of gold nanostar (AuNS). First, AuNS was prepared by a seed-mediated method in a HEPES buffer. AuNS shows two different LSPR absorbance bands at 736 nm and 550 nm, respectively. Multicolor was generated by iodide-mediated surface etching of AuNS in the presence of H₂O₂. Under the optimized conditions, the absorption peak Δλ had a good linear relationship with the concentration of H₂O₂ with a linear range from 0.67~66.67 μmol L^-1, and the detection limit is 0.44 μmol L^-1. It can be used to detect residual H₂O₂ in tap water samples. This method offered a promising visual method for point-of-care testing of H₂O₂-related biomarkers.

Efficient upcycling of iron scrap and waste polyethylene terephthalate plastic into Fe3O4@C incorporated MIL-53(Fe) as a novel electro-Fenton catalyst for the degradation of salicylic acid

The current research demonstrates the efficiency of a low-cost MIL-53(Fe)-metal-organic framework (MOF) derived Fe₃O₄@C (MIL-53(Fe)@Fe₃O₄@C) electrocatalyst in a batch-scale electro-Fenton (EF) process for the degradation of salicylic acid (SA) from wastewater. The electrocatalyst was prepared from the combination of polyethylene terephthalate (PET) and iron scrap wastes. The result showed 91.68 ± 3.61% degradation of 50 mg L^-1 of SA under optimum current density of 5.2 mA cm^-2, and pH of 7.0 during 180 min of electrolysis time. The degradation of SA from waste catalyst was similar to the chemical-based MIL-53(Fe)-derived Fe₃O₄@C (cFe) cathode catalyst. The presence of chloride ions (Cl^-) in the water matrix has shown a strong inhibitory effect on the elimination of SA, followed by nitrate (NO₃^-), and bicarbonate (HCO₃^-) ions. The multiple cyclic voltammetry (CV) analysis and reusability test of waste cathode catalyst showed only 8.03% drop of current density at the end of the 20th cycle and 5% drop of degradation efficiency after 6th cycle with low leaching of iron. The radical scavenging experiment revealed that the HO^• generated via electrochemical generation of H₂O₂ had a prominent contribution in the removal of SA compared to HO₂^•/O₂^•-. Besides, possible catalysis mechanism and degradation pathways were deduced. Furthermore, a satisfactory performance in the treatment of SA spiked in real water matrices was also observed by waste-derived Fe₃O₄@C cathode catalyst (wFe). Additionally, the total operating cost and toxicity analysis showed that the as-synthesized wFe cathode catalyst could be appropriate for removing organic pollutants from wastewater in the large-scale application.

MoS2-modified MIL-53(Fe) for synergistic adsorption-photocatalytic degradation of tetracycline

In this paper, MoS₂@MIL-53(Fe) (noted as MSMF) metal-organic backbone adsorption photocatalysts were successfully prepared by a solvothermal method. For the degradation performance of MSMF catalysts on tetracycline pollutants, the effects of MoS₂ doping ratio, reaction mode, and contaminant concentration on the degradation performance were investigated. And the materials were characterized by XRD, XPS, SEM, BET, PL, and ESR to investigate the reaction mechanism. The results showed that the optimal synthesis mass ratio of MoS₂:MIL-53 (Fe) prepared by holding at 150 °C for 10 h was 0.20:1 (20%MSMF). In the adsorption-photocatalytic synergy experiment, 87.62% of tetracycline (30 mg/L) could be removed with 0.20 g/L of 20%MSMF after 40 min of UV irradiation, while the removal of tetracycline by MoS₂ and MIL-53 (Fe) was only 35.99% and 65.40%. The characterization showed that the specific surface area and total pore volume of 20%MSMF were 1.12 and 3.12 times higher than those of MIL-53 (Fe), respectively. And the separation and transfer efficiency of electron-hole pairs were improved for 20%MSMF compared to the constituent components. These results suggest that the doping of MoS₂ enhances the adsorption and photocatalytic ability of MIL-53 (Fe) that can be used for the efficient treatment of tetracycline.

Microwave-assisted MOF@biomass layered nanomaterials: Characterization and applications in wastewater treatment

MOF@Biomass layered hybrids were designed through in situ growth from rice husk (RH) and microwave-assisted synthesized MIL-53(Al) particles that enable the reduction of reaction times. The synthesis process included steps to pretreat RH, Al adsorption on RH, and then MIL-53(Al) in-situ growth reaction at 125 °C for 60 min and 200 W irradiation power. The resulting hybrid (MIL-53(Al)@RH) and its parent separate materials were characterized using TGA, SEM, FTIR, XRD, among others. MIL-53(Al)@RH showed high crystallinity in the hybridized MOF particles, thermal decomposition phases, and functional groups (Al-O, O-H, CO, and CC). The hybrid particles allow an easy separation during heterogeneous processing due to their 400 times larger size compared to MIL-53(Al) crystals. The properties of the layered hybrids for removal of Oxytetracycline (OTC), Diclofenac (DCL), and Glyphosate (GLY) in aqueous solutions, were tested by adsorption (ADS) and advanced oxidation processes (AOP). The high ADS capacities (162 mg g^-1 GLY, 139 mg g^-1 OTC, 93 mg g^-1 DCL) and % removal in AOP (97% GLY, 91% OTC, 80% DCL) demonstrated that MIL-53(Al) maintained its properties after hybridization.

Facile synthesis of CoFe2O4@MIL-53(Al) nanocomposite for fast dye removal: Adsorption models, optimization and recyclability

The global occurrence of textile dyes pollution has recently emerged, posing a serious threat to ecological systems. To abate dye contamination, we here developed a novel magnetic porous CoFe₂O₄@MIL-53(Al) nanocomposite by incorporating magnetic CoFe₂O₄ nanoparticles with MIL-53(Al) metal-organic framework. This nanocomposite possessed a surface area of 197.144 m² g^-1 and a pore volume of 0.413 cm³ g^-1. The effect of contact time (5-120 min), concentration (5-50 mg L^-1), dosage (0.1-1.0 g L^-1), and pH (2-10) on Congo red adsorption was clarified. CoFe₂O₄@MIL-53(Al) could remove 95.85% of Cong red dye from water with an accelerated kinetic rate of 0.6544 min^-1 within 10 min. The kinetic and isotherm models showed the predominance of Bangham and Temkin. According to Langmuir, the maximum uptake capacities of CoFe₂O₄@MIL-53(Al), CoFe₂O₄, and MIL-53(Al) adsorbents were 43.768, 17.982, and 15.295 mg g^-1, respectively. CoFe₂O₄@MIL-53(Al) was selected to optimize Cong red treatment using Box-Behnken experimental design. The outcomes showed that CoFe₂O₄@MIL-53(Al) achieved the highest experimental uptake capacity of 35.919 mg g^-1 at concentration (29.966 mg L^-1), time (14.926 min), and dosage (0.486 g L^-1). CoFe₂O₄@MIL-53(Al) could treat dye mixture (methylene blue, methyl orange, Congo red, malachite green, and crystal violet) with an outstanding removal efficiency of 81.24% for 30 min, and could be reused up to five cycles. Therefore, novel recyclable and stable CoFe₂O₄@MIL-53(Al) is recommended to integrate well with real dye treatments systems.

Colorimetric detection of H2O2 with Fe3O4@Chi nanozyme modified µPADs using artificial intelligence

Peroxidase mimicking Fe₃O₄@Chitosan (Fe₃O₄@Chi) nanozyme was synthesized and used for high-sensitive enzyme-free colorimetric detection of H₂O₂. The nanozyme was characterized in comparison with  Fe₃O₄ nanoparticles (NPs) using X-ray diffraction, Fourier-transform infrared spectroscopy, dynamic light scattering, and thermogravimetric analysis. The catalytic performance of Fe₃O₄@Chi nanozyme was first evaluated by UV-Vis spectroscopy using 3,3',5,5'-tetramethylbenzidine. Unlike Fe₃O₄NPs, Fe₃O₄@Chi nanozyme exhibited an intrinsic peroxidase activity with a detection limit of 69 nM. Next, the nanozyme was applied to a microfluidic paper-based analytical device (µPAD) and colorimetric analysis was performed at varying concentrations of H₂O₂ using a machine learning-based smartphone app called "Hi-perox Sens++ ." The app with machine learning classifiers made the system user-friendly as well as more robust and adaptive against variation in illumination and camera optics. In order to train various machine learning classifiers, the images of the µPADs were taken at 30 s and 10 min by four smartphone brands under seven different illuminations. According to the results, linear discriminant analysis exhibited the highest classification accuracy (98.7%) with phone-independent repeatability at t = 30 s and the accuracy was preserved for 10 min. The proposed system also showed excellent selectivity in the presence of various interfering molecules and good detection performance in tap water.