Malachite green (MG) abuse in aquaculture has caused food safety issues and surface-enhanced Raman scattering (SERS) can be utilized to monitor MG residues in aquatic products. However, the sensitivity and accuracy of SERS detection are limited by food matrix interference. Therefore, in this study, SERS active MNP@Au@MIL-100(Fe) substrates were developed by utilizing magnetic nanoparticle (MNP) as the core, which was evenly decorated with Au nanoparticles (AuNPs), and then coated with metal–organic frameworks (MOFs) shell of MIL-100(Fe), which acted as a filter to only allow molecules with appropriate sizes to approach the inner AuNPs, thus avoiding food matrix interference and improving the identification ability to analytes. Experiments in detecting MG residues in prawns was realized with the limit of detection (LOD) of 1.32 × 10 −10 M, showing great potential for its use as a reliable SERS substrate for monitoring food contaminants.
Meng Chen,Jiaqi Yan,Ying Tan,Yongfei Li,Zhimin Wu,Langsheng Pan,Yuejin Liu
Hydroxyalkylation of phenol with formaldehyde to bisphenol F was investigated over the metal–organic frameworks of MIL-100(Fe or Cr) and MIL-101(Fe or Cr) encapsulated with Keggin phosphotungstic acid (PTA). PTA@MIL-100(Fe or Cr)(β) and PTA@MIL-101(Fe or Cr)(β) with different β values (the molar ratio of W/M, where M = Fe or Cr) were prepared and characterized by XRD, BET, FT-IR, TG, SEM, TEM, and ICP. The research results showed that PTA@MIL-100(Fe or Cr)(β) had a higher catalytic activity than PTA@MIL-101(Fe or Cr)(β). PTA@MIL-100(Fe)(0.4) was the most effective among the studied catalysts and had excellent reusability. A 92.12% product yield and 93.01% selectivity for bisphenol F could be obtained over the PTA@MIL-100(Fe)(0.40) catalyst. The effects of the reaction time, reaction temperature, catalyst concentration, and phenol/formaldehyde molar ratio on the reaction performance were also investigated. A plausible mechanism for hydroxyalkylation of phenol with formaldehyde to bisphenol F was proposed.
The uniform and stable deposition of metal-organic frameworks (MOFs) onto membranes without compromising their performance presents a significant challenge. This study reports the fabrication of a photocatalytic self-cleaning membrane using hydrothermal and photochemical substitution methods. These methods enabled the uniform and stable deposition of β-FeOOH nanorods, m-MIL-100(Fe), and Ag nanoparticles (NPs) not only on the members surface but also throughout the interior of polyvinylidene fluoride (PVDF) membrane pores. The synergistic effect of these materials and their uniform and stable distribution within the PVDF membrane resulted in superior photocatalytic efficacy. The membrane's excellent photocatalytic performance facilitated the degradation of most pollutants, ensuring prolonged usage. Unlike other photocatalytic membranes requiring additional cocatalysts, our membrane degraded over 90% of various dyes without H 2 O 2 , demonstrating a greener usage mode and higher photocatalytic efficiency. The valence band (VB) and conduction band (CB) of β-FeOOH nanorods and m-MIL-100(Fe) were calculated, confirming the existence of a type-II heterojunction for the first time. Free radical trapping experiments identified hydroxyl radicals (·OH) as the primary reactive species in the degradation process. This research provides a novel approach to uniformly and stably load MOFs on membranes, enhancing their properties and offering insights into fabricating multifunctional photocatalytic membranes.
For the first time, MIL-100(Fe)-derived microspheres with a hollow structure were perfectly constructed and used as a photocatalyst to decompose organic dyes under visible light irradiation. The prepared MIL-100(Fe)-NH2(20) could boost the separation, migration, and transfer of photoinduced carriers effectively, together with efficient photocatalytic performance. In simulated sunlight, the MIL-100(Fe)-NH2(20) exhibits the best degradation efficiency as well as excellent reusability and stability, and the degradation rate for rhodamine B (RhB) can be more than 99.5% within 80 minutes. Structural analysis proves that the porous MIL-100(Fe)-NH2(20) catalyst reaps an amazing hollow structure, large specific surface areas (2784.9 m2·g–1), and uniform distribution of Fe and N active phases. Besides, the enhanced visible light response and lower recombination rate of e––h+ pairs are both confirmed, and the band gap is significantly reduced to 2.53 eV. Finally, the photocatalytic mechanism and the possible degradation pathway were suggested. Owing to the enhanced photocatalytic activity, good tolerance to pH and water quality, and excellent stability, the MIL-100(Fe)-NH2(20) catalyst can be potentially used in a wide range of dye wastewater purifications.
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