Towards Environment Friendly Hydrothermally Synthesized Li+, Rb+, In3+ Intercalated Phosphotungstate (PW12O40) Thin Films

In the present investigation, a one-step hydrothermal approach is proposed to synthesize Li⁺, Rb⁺, and In³⁺intercalated PW₁₂O₄₀ (PTA) thin films. The photoelectrochemical performance of the deposited Li₃PW₁₂O₄₀ (Li-PTA), Rb₃PW₁₂O₄₀ (Rb-PTA), and In₃PW₁₂O₄₀ (In-PTA) photocathodes were investigated using a two-electrode cell configuration of FTO/Li₃PW₁₂O₄₀/(0.1 M I^-/I^3-)_aq./Graphite. The energy band gaps of 2.24, 2.11, and 2.13 eV were observed for the Li-PTA, Rb-PTA, and In-PTA films, respectively, as a function of Li⁺, Rb⁺, and In³⁺. The evolution of the spinal cubic crystal structure with increased crystallite size was observed for Rb⁺ intercalation within the PTA Keggin structure, which was confirmed by X-ray diffraction (XRD). Scanning electron microscopy (SEM) revealed a modification in the surface morphology from a rod-like structure to a densely packed, uniform, and interconnected microsphere to small and large-sized microspheres for Li-PTA, Rb-PTA, and In-PTA, respectively. Compositional studies confirmed that the composing elements of Li, Rb, In, P, W, and O ions are well in accordance with their arrangement for Li⁺, Rb⁺, In³⁺, P⁵⁺, W⁶⁺, and O^2- valence states. Furthermore, the J-V performance of the deposited photocathode shows power conversion efficiencies (PCE) of 1.25%, 3.03%, and 1.62%, as a function of the incorporation of Li⁺, Rb⁺, and In³⁺ ions. This work offers a one-step hydrothermal approach that is a prominent way to develop Li⁺, Rb⁺, and In³⁺ ions intercalated PTA, i.e., Li₃PW₁₂O_40, Rb₃PW₁₂O₄₀, and In₃PW₁₂O₄₀ photocathodes for competent solar energy harvesting.

Facile preparation of polyoxometalate nanoparticles via a solid-state chemical reaction for aerobic oxidative desulfurization catalysis

Polyoxometalate nanoparticles were synthesized via a concise solid-state reaction method by directly grinding silver nitrate and the polyoxometalate (NH4)5H6PMo4V8O40 at room temperature without the assistance of a surfactant. The as-prepared Ag6(NH4)5PMo4V8O40 (AgPMo4V8) comprised uniform nanoparticles of 50 nm size, which provided significant catalytic oxidative desulfurization (CODS) performance using O2, N2 + O2 or air as an oxidant. The high efficiency of 100% removal was obtained using AgPMo4V8 nanoparticles as a catalyst in treating model refractory sulfurs. The coexistence of Ag+ and PMo4V8O4011- was the main contribution for this CODS procedure, and the Ag+ species was employed as the electron transfer mediator (ETM) and the PMo4V8O4011- anion was used as the electron donor. The internal electron transfer between Ag+/Ag0 and V5+/V4+ allowed AgPMo4V8 to mimic oxygenase to release the activation energy of oxygen. AgPMo4V8 nanoparticles also exhibited potential for practical catalytic application in the CODS of diesel and gasoline to produce ultra-clean oils with a S content lower than 10 ppm under mild reaction conditions using a mixture of N2 and O2, thus favoring industrial application.

Heterogenization of polyoxometalates as solid catalysts in aerobic oxidation of glycerol

A series of heterogeneous catalysts LnPMo₁₂O₄₀ (L = Al³⁺, Fe³⁺, Cr³⁺, Ti⁴⁺, Zr⁴⁺, Zn²⁺) and HxPMo₁₁LO₃₉ (L = Zn²⁺, Cr³⁺, Fe³⁺, Al³⁺, Ti⁴⁺) were prepared using a simple calcination treatment and were evaluated in aerobic oxidation of glycerol.

Palladium-catalyzed tandem reaction of epoxynitriles with arylboronic acids in aqueous medium: divergent synthesis of furans and pyrroles

A palladium-catalyzed controllable divergent synthesis of furans and pyrroles through a cascade reaction of epoxynitriles with arylboronic acids has been developed in the aqueous phase.

Silver & gold-catalyzed routes to furans and benzofurans

Silver and gold have become incredibly versatile and mild catalysts for numerous transformations, especially in heterocycle synthesis. For the most prominent of them, i.e. furans, silver and gold, with their unique reactivity and mildness, allow numerous possible routes to highly substituted and/or functionalized furans from a large variety of starting materials. Silver and gold catalysis provide thus the most flexible way to this important family of compounds. The present review describes these silver and gold-catalyzed routes, with some emphasis on mechanistic aspects, and proposes a comparison of both the silver and the gold-catalyzed syntheses of furans.

Heterogeneous catalysis by tungsten-based heteropoly compounds

In this review, the recent works on heterogeneous catalytic applications of polyoxotungstates in liquid-phase organic reactions are reviewed.

One-Pot Conversion of Carbohydrates into Furan Derivatives via Furfural and 5-Hydroxylmethylfurfural as Intermediates

Recently, there has been growing interest in the transformation of renewable biomass into value-added fuels and chemicals. The catalytic conversion of naturally abundant carbohydrates can generate two-important furan chemicals: 5-hydroxymethylfurfural (HMF) from C6 carbohydrates and furfural from C5 carbohydrates. Both HMF and furfural have received great interest as precursors in the synthesis of commodity chemicals and liquid fuels. In recent years, a trend has emerged to integrate sequential catalytic processes involving multistep reactions for the direct one-pot transformation of carbohydrates into the aimed fuels and chemicals. One-pot reactions have remarkably unique and environmentally friendly benefits, including the fact that isolation and purification of intermediate compounds can be avoided. Herein, the present article aims to review recent advances in the one-pot conversion of carbohydrates into furan derivatives via furfural and HMF as intermediates. Special attention will be paid to the catalytic systems, mechanistic insight, reaction pathways, and catalyst stability. It is expected that this review will guide researchers to develop effective catalytic systems for the one-pot transformation of carbohydrates into furan derivatives.

Designation of highly efficient catalysts for one pot conversion of glycerol to lactic acid

Production of lactic acid from glycerol is a cascade catalytic procedure using multifunctional catalysts combined with oxidative and acidic catalytic sites. Therefore, a series of silver-exchanged phosphomolybdic acid catalysts (Ag_xH_3−xPMo₁₂O₄₀, x = 1 ~ 3, abbreviated as Ag_xPMo) was designed and applied in glycerol oxidation with O₂ as an oxidant to produce lactic acid (LA) without adding any base. Among all, total silver exchanged phosphomolybdic acid (Ag₃PMo) was found to be the most active one with LA selectivity of 93% at 99% conversion under mild conditions of 5 h at 60 °C. The exceptionally high efficiency was contributed to the generation of strong Lewis acid sites, enhanced redox potentials and water-tolerance. More importantly, Ag₃PMo was tolerant in crude glycerol from biodiesel production. And the reaction mechanism was also discussed. Meanwhile, Ag₃PMo acted as a heterogeneous catalyst for 12 recycles without loss of activity.

When CuAAC 'Click Chemistry' goes heterogeneous

Within the green chemistry context, heterogeneous catalysis is more and more applied to organic synthesis. The well known ‘click chemistry’ and especially its flagship, the copper-catalyzed azide–alkyne cycloaddition reaction (CuAAC), is now catch up by such heterogenisation process and copper ions or metals have been grafted or deposited on or into various solids, such as (bio)polymers, charcoal, silica, zeolites, POM or MOF.

Heterogenization of heteropoly compounds: a review of their structure and synthesis

The heterogenization of different types of heteropoly compoundsviasix popular methods from those published over the past recent 15 years is reviewed.

Gold(I)-catalyzed formation of furans from γ-acyloxyalkynyl ketones

Various γ-acyloxyalkynyl ketones were efficiently converted into highly substituted furans with 2.5 mol % of triflimide (triphenylphosphine)gold(I) as a catalyst in dichloroethane at 70 °C.