Hybridizing engineering strategy of decatungstate III: Transition metal modified carbon quantum dot-regulated photo-catalytic oxidation performance of decatungstate

Abstract

The selective oxidation of hydrocarbons (RH) by dioxygen (O₂) is a very important method for industrial production of bulk oxygen-containing compounds, However, due to the high chemical inertness of RH and O₂, achieving this reaction under mild conditions still faces significant challenges. This paper discloses an efficient hybridizing engineering (HE) strategy of decatungstate (DT) with 3d transition metal ions (Mⁿ⁺=Ni²⁺, Co²⁺ or Cu²⁺)-modified carbon quantum dots (Mⁿ⁺/CQD) as the dopants. Compared to pure CQD, The Mⁿ⁺/CQD can more efficiently combine with DT anion to fabricate a high-quality hybrid via electrostatic interactions, thereby bestowing the hybrid with an enhanced visible light response especially the separation efficiency of photo-generated charge pairs. Furthermore, the above hybridization effects of Mⁿ⁺/CQD on DT anion can be fine-tuned and gradually improved with a change of the metal ion from Cu²⁺, Co²⁺ to Ni²⁺, along with a continuous enhancement of the hybrid's photo-catalytic efficiency in the visible light- triggered selective oxidation of ethylbenzene with O₂ in acetonitrile. The best Ni²⁺/CQD-doped TBADT can achieve ca. 48% ethylbenzene conversion and 87.6% acetophenone selectivity in the presence of 2 M HCl, and it also shows a much higher photo-catalytic activity for the photo-oxidation of toluene, cyclohexane and benzyl alcohol compared to pure TBADT. The HE strategy with Mⁿ⁺/CQD as the cationized hybridizers is much superior to that with pure CQD or Ni²⁺ as the hybridizer in hoisting the photo-catalytic performance of DT.