Song Shi

Preparation of hydrophobic hollow silica nanospheres with porous shells and their application in pollutant removal

A series of hydrophobic hollow silica nanospheres with high specific surface areas and porous shells were successfully prepared through combination of a one-step reverse-phase microemulsion route and a simple post selective etching method. These materials owned porous shells and high specific surface areas, which were generated in the etching process. The distribution difference of organic groups among the solid nanosphere was innovatively utilized to create a different etching rate between the surface and the inner part of the solid silica nanosphere. After etching, the organic groups are still present on the surface which together with the rough surface give it hydrophobic properties and the contact angles can reach 150°. The reported materials showed good performance in the removal of 4-NP in water.

Superhydrophobic SiO2-based nanocomposite modified with organic groups as catalyst for selective oxidation of ethylbenzene

A surface organic modification strategy is utilized to design and prepare a series of superhydrophobic SiO2-based nanocomposites with cobalt ions in the bulk phase and different organic groups on the surface. Physical properties such as BET surface area, surface hydrophilicity/hydrophobicity, and water adsorption amount changed significantly with the introduction of organic groups of various chain lengths, which was confirmed by TEM, SEM, FTIR, 29Si-NMR, N2 adsorption–desorption, sessile water contact angle, and TG-DTA measurements. Surface hydrophilicity/hydrophobicity altered from hydrophilic to superhydrophobic with an increase in carbon chain length, which showed an obvious effect on the catalytic performance in selective oxidation of hydrocarbons such as ethylbenzene. Superhydrophobicity was guaranteed for high catalytic activity, and the carbon chain length of the organic group was also an important factor. Superhydrophobic Pr–Co–SiO2 that contained the propyl group was the most efficient catalyst, and the conversion of ethylbenzene reached 70.4% with O2 as an oxidant under solvent-free conditions at 393 K for 7 h, which is nearly nine times that of the hydrophilic Co–SiO2 without surface organic modification.

Efficient oxidation of ethylbenzene catalyzed by cobalt zeolitic imidazolate framework ZIF-67 and NHPI

Abstract Efficient catalytic oxidation of ethylbenzene to acetophenone was realized using the catalytic system of cobalt zeolitic imidazolate framework ZIF-67/N-hydroxyphthalimide (NHPI) under mild conditions. 95.2% conversion of ethylbenzene with 90.3% selectivity to acetophenone could be obtained at 373 K under 0.3 MPa O 2 for 9 h. The results show that there exists synergetic effect between ZIF-67 and NHPI. 1-Phenylethyl hydroperoxide (PEHP) was generated via a radical process involving the hydrogen abstraction from ethylbenzene by phthalimide N-oxyl, and subsequently effectively decomposed to acetophenone by ZIF-67.

Mesoporous strong base supported cobalt oxide as a catalyst for the oxidation of ethylbenzene

A mesoporous solid strong base was applied to support cobalt oxide to obtain a strong base-type catalyst, which showed good performance in the heterogeneous oxidation of ethylbenzene under solvent-free conditions in the temperature range of 373–403 K. It was demonstrated that the reported strong base-type catalyst could facilitate the decomposition of 1-phenyl-ethylhydroperoxide, and a high reaction rate (2.89 × 10−5 s−1) could be obtained at 403 K.

Covalent triazine framework catalytic oxidative cleavage of lignin models and organosolv lignin

Covalent triazine frameworks (CTFs) were reported to be effective in the oxidative cleavage of the lignin model compound 2-phenoxyacetophenone, as metal-free catalysts with O2, producing phenol, benzoic acid, methyl benzoate and methyl benzoylformate as the major products. Combining the detailed characterizations with the reaction results, the triazine structure with unique properties of CTFs contributes to their superior catalytic performance. Mechanism investigation, including isotope-labeling, radical trapping and intermediate verification experiments, was carried out. CTFs promoted the decomposition of peroxide and cleavage of both the C–C bond and C–O bond occurred. The catalyst was reusable and very stable under the present reaction conditions. When CTFs were applied to the catalytic oxidative cleavage of organosolv lignin, nearly 80% of β-O-4 ketone bonds of the oxidized lignin were converted, suggesting the potential of CTFs in lignin depolymerization.

Formation of Strong Basicity on Covalent Triazine Frameworks as Catalysts for the Oxidation of Methylene Compounds

Porous solid bases are increasingly attractive for applications in green chemistry and heterogeneous catalysis under relatively mild conditions. Here, covalent triazine frameworks (CTFs) were first applied as a support for the porous solid strong bases through a redox process between the base precursor KNO3 and CTFs, leading to a relatively low calcination temperature (400 °C). As a result, porous organic frameworks possessing ordered microstructures as well as strong basic sites were successfully synthesized. The materials were characterized by X-ray diffraction, Fourier transform infrared, high-resolution transmission electron microscopy, temperature programmed desorption of CO2, and so forth. The obtained solid bases displayed remarkable catalytic activity in the aerobic oxidation of methylene compounds, and the yield of fluorenones could reach 93.6% at 120 °C, which was nearly 3 times higher than that of the control catalyst. The current research may present a new idea for the construction of porous organic polymers with strong basicity.

Catalytic Oxidation of Alcohol to Carboxylic Acid with a Hydrophobic Cobalt Catalyst in Hydrocarbon Solvent.

A hydrophobic cobalt catalyst was synthesized and proved to be effective in alcohol oxidation under the assistance of hydrocarbon solvent with oxygen as the terminal oxidant. A series of catalysts with different water contact angles was applied to investigate the hydrophobic effect. Further insight into the reaction process was gained by reaction kinetics, isotopic effect, etc. It showed that the hydrocarbon solvent participated in the alcohol oxidation, and with the aid of the in situ generated free radicals, the α-C-H bond was smoothly activated and the alcohol was converted to carbonyl compounds. The hydrophobic effect promoted the alcohol oxidation by affecting the solvent oxidation.