ABSTRACT:We here first proposed a yolk−shell Co 3 O 4 @ metal−organic frameworks (MOFs) nanoreactor via a facile method to accommodate sulfate radical-based advanced oxidation processes (SR-AOPs) into its interior cavity. The mesoporous and adsorptive MOFs shells allow the rapid diffusion of reactant molecules to the encapsulated Co 3 O 4 active sites, and the confined high instantaneous concentration of reactants in the local void space is anticipated to facilitate the SR-AOPs. As a proof of concept, the nanoreactor was fully characterized and applied for catalytic degradation of 4-chlorophenol (4-CP) in the presence of peroxymonosulfate (PMS). The enhancement of SR-AOPs in the nanoreactor is demonstrated by the result that degradation efficiency of 4-CP reached almost 100% within 60 min by using the yolk−shell Co 3 O 4 @MOFs catalysts as compared to only 59.6% under the same conditions for bare Co 3 O 4 NPs. Furthermore, the applicability of this nanoreactor used in SR-AOPs was systematically investigated in terms of effect of reaction parameters and identification of intermediates and primary radical as well as mineralization of the reaction and stability of the composite. The findings of this study elucidated a new opportunity for improved environmental remediation.

A facile strategy for the fabrication of novel bouquet-shaped magnetic porous nanocomposite via grafting a covalent organic framework (COF, TpPa-1) onto the surface-modified FeO nanoparticles (FeO NPs) was reported. The magnetic TpPa-1 (a COF synthesized from 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa-1)) contains clusters of core-shell magnetic nanoparticles and interconnected porous TpPa-1 nanofibers. Thus, it possesses larger specific surface area, higher porosity, and supermagnetism, making it an ideal sorbent for enrichment of trace analytes. Its performance was evaluated by the magnetic solid-phase extraction (MSPE) of trace polycyclic aromatic hydrocarbons (PAHs) from environmental samples prior to high-performance liquid chromatographic analysis. The results indicated that the magnetic TpPa-1 possessed superior enrichment capacity of such organic compounds.

a b s t r a c tCore/shell structured magnetic Fe 3 O 4 /polydopamine (Fe 3 O 4 /PDA) nanoparticles have been successfully synthesized and developed as a magnetic solid-phase extraction (SPE) adsorbent in dispersion mode for the determination of trace polycyclic aromatic hydrocarbons (PAHs) in environmental samples. The Fe 3 O 4 /PDA synthetic procedure is simple and involves no organic solvents. Only 20 mg of Fe 3 O 4 /PDA adsorbents are required to extract PAHs from 500 mL water samples. The adsorption attains equilibrium rapidly and analysts are eluted with acetonitrile readily. The extraction efficiency is not influenced by salt concentrations up to 300 mM and pH values over the range 4-11. Under optimized conditions, the detection limits of PAHs are in the range of 0.5-1.9 ng L −1 . The accuracy of the method is evaluated by the recoveries of PAHs from environmental samples. Good recoveries (76.4-107%) with low relative standard deviations from 1.0% to 9.7% are achieved. Comparison study shows that the recoveries of target PAHs are low when they are extracted using traditional SPE method even with the addition of methanol or tetrabutylammonium bromide surfactants in water samples, suggesting great application potential of magnetic SPE method to preconcentrate highly hydrophobic contaminants (such as PAHs) from large volume of water samples. This new SPE method provides several advantages, such as simplicity, low environmental impact, high extraction efficiency, high breakthrough volumes, convenient extraction procedure, and short analysis time.