Polyoxometalates Hosted in Layered Double Hydroxides: Highly Enhanced Catalytic Activity and Selectivity in Sulfoxidation of Sulfides

Layered double hydroxides (LDHs) are a class of layered materials with tunable interlayer galleries. In this paper, a series of Mg₃Al–P₂W₁₇X (X = Mn^III, Fe^III, Zn^II, Co^II, Cu^II, Ni^II) have been prepared successfully by intercalating the polyoxometalate (POM) of [α₂-P₂W₁₇O₆₁(X·OH₂)]^<i>n</i>− ([P₂W₁₇X]^<i>n</i>−, <i>n</i> = 7 or 8) into a Mg₃Al–suberic precursor. Catalytic tests for H₂O₂-based sulfoxidation of various sulfides demonstrate that Mg₃Al–P₂W₁₇Zn exhibits better catalytic efficiency and selectivity than pure POM or LDH precursors under mild conditions. The uniform and well-ordered dispersion of POM in the confined gallery of LDHs and the multiple interactions between POMs and LDHs contribute to the excellent catalytic performance. Moreover, Mg₃Al–P₂W₁₇Zn is stable and can be easily separated from the reaction system. The recycled Mg₃Al–P₂W₁₇Zn maintains both the intact structures of the POM anion and LDHs. The scaled-up experiment provides further support for its potential use for industrial applications

DataSheet1_Variations, sources, and effects on ozone formation of VOCs during ozone episodes in 13 cities in China.docx

In recent years, ozone (O3) pollution has worsened in China and contributes frequently to air pollution problems. To support the implementation of coordinated control for ozone and fine particulate matter, it is essential to study the chemical compositions and sources of volatile organic compounds (VOCs), which are the crucial precursor of both ozone and fine particulate matter. In this study, 117 volatile organic compounds were monitored in 13 cities in Beijing-Tianjin-Hebei Urban Agglomeration and Fenwei plain. Concentrations of total volatile organic compounds ranged from 42 to 279 μg/m3 during the monitoring episode. In all 13 cities, alkanes, halogenated hydrocarbons, aromatics and oxygenated volatile organic compounds (OVOCs) were the dominant volatile organic compounds. Contributions of alkanes, halogenated hydrocarbons, aromatics and oxygenated volatile organic compounds to total ozone formation potential (OFP) were 21.7%–32.6%, 21.0%–27.9%, 24.3%–50.8% and 28.6%–52.3%, respectively. Furthermore, the results of source apportionment by positive matrix factorization (PMF) model indicated that solvent usage, gasoline evaporation, vehicle emissions, petrochemical industry and combustion were essential volatile organic compounds sources in 13 cities. Moreover, the sensitivity of ozone production was studied using an Empirical Kinetic Modeling Approach (EKMA) model, and it was found that ozone formation was volatile organic compounds limited in all 13 cities.</p