Construction and visible-light photocatalytic performance of carboxyethyltin/transition metal–functionalized wheel-like tungstophosphates

The wheel-like tungstophosphate ([P₈W₄₈O₁₈₄]⁴⁰⁻, abbreviated as P₈W₄₈) reacted with estertin trichloride (Cl₃SnRCH₃, R = CH₂CH₂COO) in aqueous solution, resulting in a new wheel-like polyoxometalate (POM) containing six SnR fragments, formulated as K₆Na₂₄[{(SnR(H₂O))₂(μ-OH)(μ-SnR(H₂O))}₂(P₈W₄₈O₁₈₄)]·59H₂O (abbreviated as Sn ₆ - P ₈ W ₄₈ ). Based on this, the transition metal (TM) was further introduced into the Sn ₆ - P ₈ W ₄₈ system, self-assembling three other wheel-like POMs with the general formula K_xNa_yH_{26 − x − y}[{TM(H₂O)₃(SnR(H₂O))₂(μ-OH)(μ-SnR(H₂O))}₂(P₈W₄₈O₁₈₄)]·nH₂O (abbreviated as TM ₂ - Sn ₆ - P ₈ W ₄₈ , TM = Mn, Co, Ni; x = 0, 1, 2; y = 19, 22, 15; n = 72, 85, 75, respectively). The structures of these new organometal and TM co-modified compounds were characterized using infrared, UV–Vis. spectroscopy, ¹¹⁹Sn NMR, and powder- and single-crystal X-ray diffraction analysis. The estertin precursor hydrolyzed into carboxyethyltin (SnR) fragment in these crystalline POM materials, which can improve their adhesion to titanium dioxide (TiO₂). The photocatalytic performance of Sn ₆ - P ₈ W ₄₈ , TM ₂ - Sn ₆ - P ₈ W ₄₈ , and their TiO₂ composites was examined by studying the degradation of a model dye pollutant Rhodamine B (RhB) under visible-light irradiation without adding hydrogen peroxide (H₂O₂), and the photocatalytic mechanism was also discussed. The experimental results show that the title compounds exhibit a quicker and better photocatalytic degradation effect on RhB compared with their parent compound, indicating that the introduced organotin groups play a significant role. Moreover, it was found that H₂O₂ was produced after illumination pretreatment for POM solution, promoting the photocatalytic reaction.     

One-step hydrolysis for the preparation of carboxylated cellulose nanofibrils with highly stable dispersibility from pomelo peel

Cellulose - One-step acid hydrolysis was successfully employed to prepare carboxylated cellulose nanofibrils (CCNFs) from pomelo peel waste with the mixture of hydrochloric acid and citric acid...     

A Free Boundary Problem for Some Modified Predator-Prey Model in a Higher Dimensional Environment

Applications of Mathematics - We focus on the free boundary problems for a Leslie-Gower predator-prey model with radial symmetry in a higher dimensional environment that is initially well populated...     

Highly stable polyoxometalate‐resorcin[4]arene‐based inorganic‐organic complexes for catalytic oxidation desulfurization

Self‐assembly of a resorcin[4]arene‐based ligand (TMR4A) with metal salts and H₃PMo₁₂O₄₀·xH₂O offers two isostructural complexes, namely, [Ni₂Cl(TMR4A)₂(CH₃CN)₂]·[PMo₁₂O₄₀]·4CH₃CN ( 1 ) and [Co₂Cl(TMR4A)₂(CH₃CN)₂]·[PMo₁₂O₄₀]·4CH₃CN ( 2 ). In both 1 and 2 , one Cl^? anion bridges two metal cations, and each metal cation is further chelated by four 2‐mercaptopyridine N‐oxide groups of one TMR4A, producing a [M₂Cl(TMR4A)₂]³⁺ dimer (M = Ni or Co). The negative [PMo₁₂O₄₀]^3? as a counter‐anion balances the positive charge. Markedly, 1 and 2 exhibit high stability in aqueous solutions with different pH values and in organic solvents. Remarkably, the efficient heterogeneous catalytic capability for oxidative desulfurization was studied by suing 1 and 2 as recycled catalysts. Moreover, the electrochemical behaviors of the two compounds were discussed as well.     

Multimetallic Oxynitrides Nanoparticles for a New Generation of Photocatalysts

A versatile synthetic strategy for the preparation of multimetallic oxynitrides has been designed and here exemplarily discussed considering the preparation of nanoscaled zinc–gallium oxynitrides and zinc–gallium–indium oxynitrides, two important photocatalysts of new generation, which proved to be active in key energy related processes from pollutant decomposition to overall water splitting. The synthesis presented here allows the preparation of small nanoparticles (less than 20 nm in average diameter), well-defined in size and shape, yet highly crystalline and with the highest surface area reported so far (up to 80 m² g⁻¹). X-ray diffraction studies show that the final material is not a mixture of single oxides but a distinctive compound. The photocatalytic properties of the oxynitrides have been tested towards the decomposition of an organic dye (as a model reaction for the decomposition of air pollutants), showing better photocatalytic performances than the corresponding pure phases (reaction constant 0.22 h⁻¹), whereas almost no reaction was observed in absence of catalyst or in the dark. The photocatalysts have been also tested for H₂ evolution (semi-reaction of the water splitting process) with results comparable to the best literature values but leaving room for further improvement.     

Enantioselective Total Synthesis of Pseudopteroxazole and Ileabethoxazole

Enantioselective total syntheses of pseudopteroxazole ( 1 ) and ileabethoxazole ( 2 ) are presented. The two original stereocenters were constructed in excellent enantioselectivity and good diastereoselectivity through Carreira's asymmetric dual catalytic allylation, which shows potential for accessing diastereoisomers at C2 and C3 of 1 and 2 . Cationic cyclizations of 13 and 24 demonstrated an effective pathway for the construction of the opposite configurations at C1 in 1 and 2 . Additionally, an approach for the introduction of methyl at C4 is a feasible solution for structural modifications at C4 in 1 and 2 .     

The Role of Polarization in Photocatalysis

Semiconductor photocatalysis as a desirable technology shows great potential in environmental remediation and renewable energy generation, but its efficiency is severely restricted by the rapid recombination of charge carriers in the bulk phase and on the surface of photocatalysts. Polarization has emerged as one of the most effective strategies for addressing the above‐mentioned issues, thus effectively promoting photocatalysis. This review summarizes the recent advances on improvements of photocatalytic activity by polarization‐promoted bulk and surface charge separation. Highlighted is the recent progress in charge separation advanced by different types of polarization, such as macroscopic polarization, piezoelectric polarization, ferroelectric polarization, and surface polarization, and the related mechanisms. Finally, the strategies and challenges for polarization enhancement to further enhance charge separation and photocatalysis are discussed.     

The antipode of a quasitriangular quasi-Turaev group coalgebra is bijective

In order to construct a class of new Turaev-braided group category with nontrivial associativity, the concept of a quasitriangular quasi-Turaev group coalgebras was recently introduced. Inside the definition, the conditions of invertibility of the R-matrix R and bijectivity of the antipode S are required. In this article, we prove that the antipode of a quasitriangular quasi-Turaev group coalgebra without the assumptions about invertibility of the antipode and R-matrix is inner, and a fortiori, bijective. As an application, we prove that for a quasitriangular quasi-Turaev group coalgebra, two conditions mentioned above are unnecessary.