Mechanistic Investigation of Thermal and Photoreactions between Boron and Silane.

Density functional theory and high-level ab initio calculations were performed to elucidate the detailed reaction mechanism from B and SiH4 to a structure with two bridging H atoms (Si(µ-H2)BH2, silicon tetrahydroborate). On the basis of the calculated results, this reaction mechanism includes both thermal and photochemical reactions. Especially, thermal conversion of silylene dihydroborate (H2B═SiH2) to Si(µ-H2)BH2 is not feasible because two high energetic barriers must be overcome. In contrast, the reverse reaction is feasible because it is effectively only necessary to overcome a single barrier. The characteristics of the excited states of H2B═SiH2 and Si(µ-H2)BH2 have been identified. Two successive conical intersections (CIs) are involved in the photochemical reaction. The BSiH4 bending coordinate is almost parallel to the reaction coordinate near the regions from the second CI to Si(µ-H2)BH2. The activated BSiH4 bending mode lift the degeneracy of the second CI, thereby the reaction readily proceeds to Si(µ-H2)BH2. All calculated results in this work reasonably well describe the recent experimental observations.

Hierarchical BiOI nanostructures supported on a metal organic framework as efficient photocatalysts for degradation of organic pollutants in water.

Semiconductor-based photocatalysis is a green method for the removal of toxic organic pollutants by decomposition into harmless products. However, traditional single-component semiconductors are unable to reach high degradation efficiencies due to excessive photo charge carrier recombination. The use of hybrid nanocomposite photocatalysts is a promising strategy for overcoming this problem by reducing recombination as well as ensuring that large amounts of solar energy are harvested. Herein, a novel visible-light-active hybrid nanocomposite, BiOI/MIL-88B(Fe), was successfully synthesized through a simple precipitation method. In the BiOI/MIL-88B(Fe) composite, both BiOI and MIL-88B(Fe) have improved charge carrier separation and reduced recombination via a simple Z-scheme mechanism. Photocatalytic degradation of the pollutant RhB was carried out during irradiation of the as-synthesized composites with simulated solar light, and the BiOI/MIL-88B(Fe) (2 wt%) composite was found to exhibit the highest photocatalytic activity among the composites. In addition, colorless phenol and ciprofloxacin (CIP) degradation experiments were also performed to confirm the visible light photocatalytic performance of the BiOI/MIL-88B(Fe) hybrid nanocomposite. Scavenger experiments, PL analysis, NBT transformations, and TA-PL experiments all supported the proposed Z-scheme mechanism of the BiOI/MIL-88B(Fe) composite photocatalyst. Moreover, simple separation from solution provides this 3D composite with good reusability and long-term stability.

Benchmark Study of Density Functional Theory for Neutral Gold Clusters, Aun (n = 2-8).

Neutral gold clusters, Aun (n = 2-8), were optimized using coupled cluster singles and doubles with perturbative triples (CCSD(T)) with a triple-ζ-level basis set to develop reliable reference values for their structural and energy parameters in order to assess the performance of density functionals. The performance of 44 density functional theory (DFT) methods for calculating molecular structures and relative energies is assessed with respect to CCSD(T). In addition, their performance when calculating vertical ionization potentials (vIPs) of Aun (n = 2-8) is also assessed by comparison with experimental values. The revTPSS functional shows good performance for calculating both the structural and energy properties of Aun (n = 2-8), whereas B3P86 shows a remarkable performance in calculating the vIPs. The quadruple-ζ-level valence basis set is necessary for obtaining accurate energy values in CCSD(T) calculations.

Ab Initio Investigation of the Ground States of F2P(S)N, F2PNS, and F2PSN.

A recent spectroscopic experiment identified difluorothiophosphoryl nitrene (F2P(S)N) and found that it showed rich photochemistry. However, a discrepancy between the experimental results and the quantum chemical calculations was reported. Thus, high-level ab initio calculations using the coupled cluster singles and doubles with perturbative triples and second-order multiconfigurational perturbation theory were performed to elucidate this inconsistency. The discrepancy arose due to the failure to consider the triplet state of difluoro(thionitroso)phosphine (F2PNS). In this work, we identify that the global minimum of the system is the triplet state of F2PNS, which allows us to explain the inconsistency between the experimental and theoretical results. All calculated results give consistent results with the recent experimental results.