Selective oxidation of benzene to phenol using functionalized membrane via Fenton-like process

Selective hydroxylation of benzene to phenol via CuII(μ-O˙)CuII intermediate using a nonsymmetric dicopper catalyst

The one-step oxidation of benzene to phenol represents a significant and promising advancement in modern industries focused on the production of high-value-added chemical products. Nevertheless, challenges persist in achieving sufficient catalytic selectivity and preventing over-oxidation. Inspired by copper enzymes, we present a nonsymmetric dicopper complex ([CuII2(TPMAN)(μ-OH)(H2O)]3+, 1) for the selective oxidation of benzene to phenol. Utilizing H2O2 as the oxidant, complex 1 demonstrates remarkable catalytic activity (a TON of 14 000 within 29 hours) and selectivity exceeding 97%, comparable to the finest homogeneous catalyst derived from first-row transition metals. It is noteworthy that the significant substituent effect, alongside a negligible kinetic isotope effect (KIE = 1.05), radical trapping experiments, and an inconsistent standard selectivity test of the ˙OH radicals, all contradict the conventional Fenton mechanism and rebound pathway. Theoretical investigations indicate that the active CuII(μ-O˙)CuII-OH species generated through the cleavage of the O-O bond in the CuII(μ-1,1-OOH)CuI intermediate facilitates the hydroxylation of benzene via an electrophilic attack mechanism. The nonsymmetric coordination geometry is crucial in activating H2O2 and in the process of O-O bond cleavage.

The stabilization of ultrafiltration membrane blended with randomly structured amphiphilic copolymer: Micropollutants adsorption properties in filtration processes

In this study, a blend membrane consisting of polyvinylidene fluoride (PVDF) and tertiary amine containing random copolymer poly(methyl methacrylate-r-dimethylamino-2-ethyl methacrylate) (P(MMA-r-DMAEMA)) was fabricated and utilized as an adsorptive membrane for micropollutants (anionic dye and heavy metal ions) removal from aqueous solutions. Cross-linking the random copolymer by p-xylylene dichloride (XDC) produced the membrane with improved copolymer retention ratio and stability, while slightly variated physicochemical properties. Besides, the fluxes of crosslinked blend membranes dramatically increased from 0.7 ± 0.1 L/(m²h) to 118.6 ± 5.9 L/(m²h). Then the present blend membrane was carried out adsorption and filtration experiments to investigate the influence of various of operation parameters including initial solution pH value, contacting time, initial solution concentration, and recycling efficiency on micropollutants removal. The experimental results showed that the removal of the anionic dyes and heavy metal ions on this tertiary amine containing blend membrane was a pH-dependent process with the maximum adsorption capacity at the initial solution pH of 3.5 for anionic dyes and 6.0 for metal ions, respectively. The membrane showed highly efficient capture of sunset yellow (above 99%). Meanwhile, the captured sunset yellow was recovered and concentrated with a small volume of alkaline solutions at pH 10.0, which simultaneously regenerated the membrane for its reuse. In a 3-cycle capture-recovery test, the membrane demonstrated a high sunset yellow recovery ratio and a volumetric concentration ratio as high as 400%. Our study provides an alternative strategy for functionalized membrane fabrication, micropollutants removal and recovery.