Pseudohomogeneous metallic catalyst based on tungstate-decorated amphiphilic carbon quantum dots for selective oxidative scission of alkenes to aldehyde

Abstract

Herein, we present an interesting role of tungstate-decorated amphiphilic carbon quantum dots (A-CQDs/W) in the selective oxidative cleavage of alkenes to aldehydes. In this work, for the first time, we disclose an unprecedented tungstate-based oxidative system incorporating A-CQDs as a bridge to the homogeneous catalyst for selective and efficient cleavage of a wide substrate scope of alkenes into aldehydes. The A-CQDs/W were synthesized via a one-step hydrothermal synthesis approach using 1-aminopropyl-3-methyl-imidazolium chloride and stearic acid for the surface modification, following by anion-exchange to immobilize WO4–2 to A-CQDs. The A-CQDs/W act as a pseudohomogeneous metallic catalyst (PMC) for selective oxidative scission of alkenes under phase transfer catalysts (PTC) free condition without over oxidation to acids, using water and H2O2 as a green oxidant. Thanks to the sub-nanometric size and novel engineered chemical structure, this PMC and reactants are in the same phase, besides they can be easily isolated from each other by extraction processes. The synthesized PMC exhibited excellent solubility and stability in various solvents. Interestingly, the system’s high conversion efficiency was preserved even after eight catalytic cycles indicating the recyclability of the synthesized PMC. We believe that this study provides a significant and conceptually novel advance in oxidative cleavage chemistry.

Ultrasound-assisted pseudohomogeneous tungstate catalyst for selective oxidation of alcohols to aldehydes

“…3 a. According to spectra, two characteristic peaks centered at 230 nm and 300–400 nm are attributed to π → π* and n → π* transitions, which are related to aromatic conjugated sp 2 systems and non-bonding electrons respectively 23 , 36 . This evidence confirms the formation of CQDs core in both samples.…”

“…In order to identify the surface functional groups of A-CQDs and A-CQDs/W, FTIR analysis, was performed 23 . As can be seen in Fig.…”

“…A-CQDs and A-CQDs/W were prepared as reported in our previous works 32 , in a typical hydrothermal method, Citric Acid (3 mmol), [APMIm][Cl] (4.5 mmol), Stearic Acid (1 mmol) and 1,2-Bis(3-aminopropylamino) ethane (3 mmol) were added to a solution contain of (1:2) ratio of (H 2 O: EtOH) in a round bottom balloon and sonicated for 5 min in ultrasonic bath. As obtained mixture transferred to a Teflon-lined stainless-steel autoclave of 25 ml and heated at 200 °C for 4 h under N 2 .…”

“…In terms of metal type, this catalyst could be regarded as one of the most low-cost catalysts as tungstate is a inexpensive metal with invaluable features such as great catalytic activity, non-toxicity, availability, good oxygen carriage ability, and great capability towards activating H 2 O 2 which makes it an appealing item for oxidation purposes. The reason why tungstate base catalysts sometimes are considered as pricey catalysts has something to do with the wrong choice of support and the methods through which tungstate is loaded on support 18 – 20 , 22 , 23 .…”

Introducing rGO@Fe3O4@Ni as an efficient magnetic nanocatalyst for the synthesis of tetrahydrobenzopyranes via multicomponent coupling reactions of dimedone, malononitrile, and aromatic aldehydes

“…The application of carbon derivatives as supports can be seen, for example, in tungstate‐decorated amphiphilic carbon quantum dot nanocomposites, which were reported as efficient catalysts for selective oxidative scission of alkenes to aldehydes and oxidation of alcohols. [ 10,11 ] MOFs have also been reported as support substrates for nanomaterials in the literature. For instance, the catalytic performances of the bulk and nanosized MOFs with different functional groups were evaluated in Knoevenagel reaction under mild and green conditions.…”