Modular polyoxometalate-layered double hydroxide composites as efficient oxidative catalysts

The exploitation of intercalation techniques in the field of two-dimensional layered materials offers unique opportunities for controlling chemical reactions in confined spaces and developing nanocomposites with desired functionality. In this paper, we demonstrate the exploitation of the novel and facile ‘one-pot’ anion-exchange method for the functionalization of layered double hydroxides (LDHs). As a proof of concept, we demonstrate the intercalation of a series of polyoxometalate (POM) clusters, Na3[PW12O40]•15H2O (Na3PW12), K6[P2W18O62]•14H2O (K6P2W18), and Na9LaW10O36•32H2O (Na9LaW10) into tris(hydroxymethyl)amino-methane (Tris) modified layered double hydroxides (LDHs) under ambient conditions without the necessity of degassing CO2. Investigation of the resultant intercalated materials of Tris-LDHs-PW12 (1), Tris-LDH-P2W18 (2), and Tris-LDH-LaW10 (3) for the degradation of methylene blue (MB), rhodamine B (RB) and crystal violet (CV) has been carried out, where Tris-LDH-PW12 reveals the best performance in the presence of H2O2. Additionally, degradation of a mixture of RB, MB and CV by Tris-LDH-PW12 follows the order of CV > MB > RB, which is directly related to the designed accessible area of the interlayer space. Also, the composite can be readily recycled and reused at least ten cycles without measurable decrease of activity

Calculations of optical rotation: Influence of molecular structure

Ab initio Hartree-Fock (HF) method and Density Functional Theory (DFT) were used to calculate the optical rotation of 26 chiral compounds. The effects of theory and basis sets used for calculation, solvents influence on the geometry and values of calculated optical rotation were all discussed. The polarizable continuum model, included in the calculation, did not improve the accuracy effectively, but it was superior to γs. Optical rotation of five or sixmembered of cyclic compound has been calculated and 17 pyrrolidine or piperidine derivatives which were calculated by HF and DFT methods gave acceptable predictions. The nitrogen atom affects the calculation results dramatically, and it is necessary in the molecular structure in order to get an accurate computation result. Namely, when the nitrogen atom was substituted by oxygen atom in the ring, the calculation result deteriorated

Inverse problem of recoverying a time-dependent nonlinearity appearing in third-order nonlinear acoustic equations

In this paper, we consider the inverse problem of recovering a time-dependent nonlinearity for a third order nonlinear acoustic equation, which is known as the Jordan-Moore-Gibson-Thompson equation (J-M-G-T equation for short). This third order in time equation arises, for example, from the wave propagation in viscous thermally relaxing fluids. The well-posedness of the nonlinear equation is obtained for the small initial and boundary data. By the higher order linearization to the nonlinear equation, and construction of complex geometric optics (CGO for short) solutions for the linearized equation, we derive the uniqueness of recovering the nonlinearity

Efficient concurrent removal of sulfur and nitrogen contents from complex oil mixtures by using polyoxometalate-based composite materials

The increasingly stringent regulations in relation to the environmental impact of employed industrial processes make compulsory the development of alternative routes towards the reduction of sulfur and nitrogen contents in large scale chemical mixtures. Herein, we demonstrate for the first time the highly efficient application of polyoxometalate (POMs)/layered double hydroxide (LDHs) composites in deep desulfurization (1000 ppm) and denitrogenation (100 ppm) of a complex model oil system under mild conditions (65 °C), with a corresponding decrease of the content to less than 10 and 1 ppm, respectively. The high efficiency of the heterogeneous catalyst along with the high stability and easy recovery of the catalytic system renders them promising candidates for greener catalytic applications

Demystify the mixed-parity pairing of attractive fermions with spin-orbit coupling in optical lattice

The admixture of spin-singlet and spin-triplet pairing states in superconductors can be typically induced by breaking spatial inversion symmetry. Employing the {\it numerically exact} auxiliary-field Quantum Monte Carlo method, we study such mixed-parity pairing phenomena of attractive fermions with Rashba spin-orbit coupling (SOC) in two-dimensional optical lattice at finite temperature. We systematically demystify the evolution of the essential pairing structure in both singlet and triplet channels versus the temperature, fermion filling, SOC and interaction strengths, via computing the condensate fraction and pair wave function. Our numerical results reveal that the singlet channel dominates in the fermion pairing and the triplet pairing has relatively small contribution to the superfluidity for physically relevant parameters. In contrast to the singlet channel mainly consisted of the on-site Cooper pairs, the triplet pairing has plentiful patterns in real space with the largest contributions from several nearest neighbors. As the SOC strengh increases, the pairing correlation is firstly enhanced and then suppressed for triplet pairing while it's simply weakened in singlet channel. We have also obtained the Berezinskii-Kosterlitz-Thouless transition temperatures through the finite-size analysis of condensate fraction. Our results can serve as quantitative guide for future optical lattice experiments as well as accurate benchmarks for theories and other numerical methods.Comment: 14 pages, 11+5 figure